Higgs physics at LHC

Indian Academy of Sciences (India)

The large hadron collider (LHC) and its detectors, ATLAS and CMS, are being built to study TeV scale physics, and to fully understand the electroweak symmetry breaking mechanism. The Monte-Carlo simulation results for the standard model and minimal super symmetric standard model Higgs boson searches and ...

The Nobel Prize winner in physics 2013--Peter Higgs

International Nuclear Information System (INIS)

Liu Jinyan

2014-01-01

Peter Higgs is a famous English physicist who was known for his works on Higgs mechanism and Higgs particle. He won the 2013 Noble Prize in physics. This paper briefly outlines his life, the proposition of Higgs mechanism and the origin of the name of Higgs particle. The discovery of Higgs particle is also given here. (author)

Introduction to the physics of Higgs bosons

International Nuclear Information System (INIS)

Dawson, S.

1994-11-01

A basic introduction to the physics of the Standard Model Higgs boson is given. We discuss Higgs boson production in e + e - and hadronic collisions and survey search techniques at future accelerators. The Higgs bosons of the minimal SUSY model are briefly considered. Indirect limits from triviality arguments, vacuum stability and precision measurements at LEP are also presented

Precision Higgs Boson Physics and Implications for Beyond the Standard Model Physics Theories

International Nuclear Information System (INIS)

Wells, James

2015-01-01

The discovery of the Higgs boson is one of science's most impressive recent achievements. We have taken a leap forward in understanding what is at the heart of elementary particle mass generation. We now have a significant opportunity to develop even deeper understanding of how the fundamental laws of nature are constructed. As such, we need intense focus from the scientific community to put this discovery in its proper context, to realign and narrow our understanding of viable theory based on this positive discovery, and to detail the implications the discovery has for theories that attempt to answer questions beyond what the Standard Model can explain. This project's first main object is to develop a state-of-the-art analysis of precision Higgs boson physics. This is to be done in the tradition of the electroweak precision measurements of the LEP/SLC era. Indeed, the electroweak precision studies of the past are necessary inputs to the full precision Higgs program. Calculations will be presented to the community of Higgs boson observables that detail just how well various couplings of the Higgs boson can be measured, and more. These will be carried out using state-of-the-art theory computations coupled with the new experimental results coming in from the LHC. The project's second main objective is to utilize the results obtained from LHC Higgs boson experiments and the precision analysis, along with the direct search studies at LHC, and discern viable theories of physics beyond the Standard Model that unify physics to a deeper level. Studies will be performed on supersymmetric theories, theories of extra spatial dimensions (and related theories, such as compositeness), and theories that contain hidden sector states uniquely accessible to the Higgs boson. In addition, if data becomes incompatible with the Standard Model's low-energy effective lagrangian, new physics theories will be developed that explain the anomaly and put it into a more

vh@nnlo-v2: new physics in Higgs Strahlung

Science.gov (United States)

Harlander, Robert V.; Klappert, Jonas; Liebler, Stefan; Simon, Lukas

2018-05-01

Introducing version 2 of the code vh@nnlo [1], we study the effects of a number of new-physics scenarios on the Higgs-Strahlung process. In particular, the cross section is evaluated within a general 2HDM and the MSSM. While the Drell-Yan-like contributions are consistently taken into account by a simple rescaling of the SM result, the gluon-initiated contribution is supplemented by squark-loop mediated amplitudes, and by the s-channel exchange of additional scalars which may lead to conspicuous interference effects. The latter holds as well for bottom-quark initiated Higgs Strahlung, which is also included in the new version of vh@nnlo. Using an orthogonal rotation of the three Higgs CP eigenstates in the 2HDM and the MSSM, vh@nnlo incorporates a simple means of CP mixing in these models. Moreover, the effect of vector-like quarks in the SM on the gluon-initiated contribution can be studied. Beyond concrete models, vh@nnlo allows to include the effect of higher-dimensional operators on the production of CP-even Higgs bosons. Transverse momentum distributions of the final state Higgs boson and invariant mass distributions of the Vϕ final state for the gluon- and bottom-quark initiated contributions can be studied. Distributions for the Drell-Yan-like component of Higgs Strahlung can be included through a link to MCFM. vh@nnlo can also be linked to FeynHiggs and 2HDMC for the calculation of Higgs masses and mixing angles. It can also read these parameters from an SLHA-file as produced by standard spectrum generators. Throughout the manuscript, we highlight new-physics effects in various numerical examples, both at the inclusive level and for distributions.

Multi-Higgs doublet models: physical parametrization, sum rules and unitarity bounds

Science.gov (United States)

Bento, Miguel P.; Haber, Howard E.; Romão, J. C.; Silva, João P.

2017-11-01

If the scalar sector of the Standard Model is non-minimal, one might expect multiple generations of the hypercharge-1/2 scalar doublet analogous to the generational structure of the fermions. In this work, we examine the structure of a Higgs sector consisting of N Higgs doublets (where N ≥ 2). It is particularly convenient to work in the so-called charged Higgs basis, in which the neutral Higgs vacuum expectation value resides entirely in the first Higgs doublet, and the charged components of remaining N - 1 Higgs doublets are mass-eigenstate fields. We elucidate the interactions of the gauge bosons with the physical Higgs scalars and the Goldstone bosons and show that they are determined by an N × 2 N matrix. This matrix depends on ( N - 1)(2 N - 1) real parameters that are associated with the mixing of the neutral Higgs fields in the charged Higgs basis. Among these parameters, N - 1 are unphysical (and can be removed by rephasing the physical charged Higgs fields), and the remaining 2( N - 1)2 parameters are physical. We also demonstrate a particularly simple form for the cubic interaction and some of the quartic interactions of the Goldstone bosons with the physical Higgs scalars. These results are applied in the derivation of Higgs coupling sum rules and tree-level unitarity bounds that restrict the size of the quartic scalar couplings. In particular, new applications to three Higgs doublet models with an order-4 CP symmetry and with a Z_3 symmetry, respectively, are presented.

Higgs physics at a future e+e- linear collider

International Nuclear Information System (INIS)

Schumacher, M.

2001-01-01

This letter reviews the potential of a high luminosity e + e - linear collider (LC) in the precision study of the Higgs boson profile. The complementarity with the large hadron collider (LHC) Higgs physics program is briefly discussed. At the LC the Higgs mass can be best measured exploiting the kinematics in the Higgs-strahlung process: e + e - → Z → ZH. Spin, parity and charge-conjugation quantum numbers of the Higgs boson can be determined in a model-independent way. At the LC the Higgs boson production and decay rates can be used to measure the Higgs couplings to gauge bosons and fermions. Several extensions of the SM model introduce additional Higgs doublets and singlets. A no loose theorem guarantees that in a general supersymmetric model embedded in a GUT scenario at least one Higgs boson will be observable at √s = 500 GeV with L = 500 fb -1 . At the LHC the SM Higgs boson or at least one Higgs boson in the MSSM will be observed. Beyond its discovery a limited number of measurements of Higgs boson properties can be carried out at the LHC (mass, total width for a heavy Higgs boson, some ratios of couplings). The complementary of LC over LHC concerning the Higgs sector is threefold: first the accuracy of these measurements will be increased, secondly the absolute measurements of all the relevant Higgs boson couplings, including the Higgs self coupling, will be possible only at LC, and finally extended Higgs sector scenarios can be observed at LC closing the loopholes of a possible non-discovery at the LHC

Higgs boson mass and new physics

International Nuclear Information System (INIS)

Bezrukov, Fedor; Brookhaven National Lab., Upton, NY; Kalmykov, Mikhail Yu.; Kniehl, Bernd A.; Shaposhnikov, Mikhail

2012-05-01

We discuss the lower Higgs boson mass bounds which come from the absolute stability of the Standard Model (SM) vacuum and from the Higgs inflation, as well as the prediction of the Higgs boson mass coming from asymptotic safety of the SM. We account for the 3-loop renormalization group evolution of the couplings of the Standard Model and for a part of two-loop corrections that involve the QCD coupling α s to initial conditions for their running. This is one step above the current state of the art procedure (''one-loop matching-two-loop running''). This results in reduction of the theoretical uncertainties in the Higgs boson mass bounds and predictions, associated with the Standard Model physics, to 1-2 GeV. We find that with the account of existing experimental uncertainties in the mass of the top quark and α s (taken at 2σ level) the bound reads M H ≥ M min (equality corresponds to the asymptotic safety prediction), where M min =129±6 GeV. We argue that the discovery of the SM Higgs boson in this range would be in agreement with the hypothesis of the absence of new energy scales between the Fermi and Planck scales, whereas the coincidence of M H with M min would suggest that the electroweak scale is determined by Planck physics. In order to clarify the relation between the Fermi and Planck scale a construction of an electron-positron or muon collider with a center of mass energy ∝200+200 GeV (Higgs and t-quark factory) would be needed.

Higgs boson mass and new physics

Energy Technology Data Exchange (ETDEWEB)

Bezrukov, Fedor [Connecticut Univ., Storrs, CT (United States). Dept. of Physics; Brookhaven National Lab., Upton, NY (United States). RIKEN-BNL Research Center; Kalmykov, Mikhail Yu.; Kniehl, Bernd A. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Shaposhnikov, Mikhail [Ecole Polytechnique Federale de Lausanne (Switzerland). Inst. de Theorie des Phenomenes Physiques

2012-05-15

We discuss the lower Higgs boson mass bounds which come from the absolute stability of the Standard Model (SM) vacuum and from the Higgs inflation, as well as the prediction of the Higgs boson mass coming from asymptotic safety of the SM. We account for the 3-loop renormalization group evolution of the couplings of the Standard Model and for a part of two-loop corrections that involve the QCD coupling {alpha}{sub s} to initial conditions for their running. This is one step above the current state of the art procedure (''one-loop matching-two-loop running''). This results in reduction of the theoretical uncertainties in the Higgs boson mass bounds and predictions, associated with the Standard Model physics, to 1-2 GeV. We find that with the account of existing experimental uncertainties in the mass of the top quark and {alpha}{sub s} (taken at 2{sigma} level) the bound reads M{sub H} {>=} M{sub min} (equality corresponds to the asymptotic safety prediction), where M{sub min}=129{+-}6 GeV. We argue that the discovery of the SM Higgs boson in this range would be in agreement with the hypothesis of the absence of new energy scales between the Fermi and Planck scales, whereas the coincidence of M{sub H} with M{sub min} would suggest that the electroweak scale is determined by Planck physics. In order to clarify the relation between the Fermi and Planck scale a construction of an electron-positron or muon collider with a center of mass energy {proportional_to}200+200 GeV (Higgs and t-quark factory) would be needed.

Concepts of electroweak symmetry breaking and Higgs physics

International Nuclear Information System (INIS)

Gomez-Bock, M.; Zerwas, P.M.; RWTH Aachen; Univ. Paris- Sud, Orsay

2007-12-01

We present an introduction to the basic concepts of electroweak symmetry breaking and Higgs physics within the Standard Model and its supersymmetric extensions. A brief overview will also be given on alternative mechanisms of electroweak symmetry breaking. In addition to the theoretical basis, the present experimental status of Higgs physics and prospects at the Tevatron, the LHC and e + e - linear colliders are discussed. (orig.)

Concepts of electroweak symmetry breaking and Higgs physics

Energy Technology Data Exchange (ETDEWEB)

Gomez-Bock, M. [Benemerita Univ., Puebla (Mexico). Inst. de Fisica; Mondragon, M. [Universidad Nacional Autonoma de Mexico, Mexico City (Mexico). Inst. de Fisica; Muehlleitner, M. [Laboratoire d' Annecy-Le-Vieux de Physique Theorique, 74 (France)]|[CERN - European Organization for Nuclear Research, Geneva (Switzerland). Theory Div.; Spira, M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Zerwas, P.M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[RWTH Aachen (Germany). Inst. Theor. Physik E]|[Univ. Paris- Sud, Orsay (France). Laboratoire de Physique Theorique

2007-12-15

We present an introduction to the basic concepts of electroweak symmetry breaking and Higgs physics within the Standard Model and its supersymmetric extensions. A brief overview will also be given on alternative mechanisms of electroweak symmetry breaking. In addition to the theoretical basis, the present experimental status of Higgs physics and prospects at the Tevatron, the LHC and e{sup +}e{sup -} linear colliders are discussed. (orig.)

SEARCHING FOR HIGGS BOSONS AND NEW PHYSICS AT HADRON COLLIDERS

International Nuclear Information System (INIS)

Chung Kao

2007-01-01

The objectives of research activities in particle theory are predicting the production cross section and decay branching fractions of Higgs bosons and new particles at hadron colliders, developing techniques and computer software to discover these particles and to measure their properties, and searching for new phenomena and new interactions at the Fermilab Tevatron and the CERN Large Hadron Collider. The results of our project could lead to the discovery of Higgs bosons, new particles, and signatures for new physics, or we will be able to set meaningful limits on important parameters in particle physics. We investigated the prospects for the discovery at the CERN Large Hadron Collider of Higgs bosons and supersymmetric particles. Promising results are found for the CP-odd pseudoscalar (A 0 ) and the heavier CP-even scalar (H 0 ) Higgs bosons with masses up to 800 GeV. Furthermore, we study properties of the lightest neutralino (χ 0 ) and calculate its cosmological relic density in a supersymmetric U(1)(prime) model as well as the muon anomalous magnetic moment a μ = (g μ -2)/2 in a supersymmetric U(1)(prime) model. We found that there are regions of the parameter space that can explain the experimental deviation of a μ from the Standard Model calculation and yield an acceptable cold dark matter relic density without conflict with collider experimental constraints. Recently, we presented a complete next-to-leading order (NLO) calculation for the total cross section of inclusive Higgs pair production via bottom-quark fusion (b(bar b) to hh) at the CERN Large Hadron Collider (LHC) in the Standard Model and the minimal supersymmetric model. We plan to predict the Higgs pair production rate and to study the trilinear coupling among the Higgs bosons. In addition, we have made significant contributions in B physics, single top production, charged Higgs search at the Fermilab as well as in grid computing for both D0 and ATLAS

ATLAS Higgs Physics Prospects at the High Luminosity LHC

CERN Document Server

Varol, Tulin; The ATLAS collaboration

2017-01-01

The Higgs physics prospects at the high-luminosity LHC are presented, assuming an energy of $\\sqrt s = 14$ TeV and a data sample of 3000-4000 fb$^{-1}$. In particular, the ultimate precision attainable on the couplings measurements of the 125 GeV Higgs boson with SM fermions and bosons is discussed, as well as perspectives on the search for the Standard Model di-Higgs production, which could lead to the measurement of the Higgs boson self-coupling.

(No) Eternal inflation and precision Higgs physics

International Nuclear Information System (INIS)

Arkani-Hamed, Nima; Dubovsky, Sergei; Senatore, Leonardo; Villadoro, Giovanni

2008-01-01

Even if nothing but a light Higgs is observed at the LHC, suggesting that the Standard Model is unmodified up to scales far above the weak scale, Higgs physics can yield surprises of fundamental significance for cosmology. As has long been known, the Standard Model vacuum may be metastable for low enough Higgs mass, but a specific value of the decay rate holds special significance: for a very narrow window of parameters, our Universe has not yet decayed but the current inflationary period can not be future eternal. Determining whether we are in this window requires exquisite but achievable experimental precision, with a measurement of the Higgs mass to 0.1 GeV at the LHC, the top mass to 60 MeV at a linear collider, as well as an improved determination of α s by an order of magnitude on the lattice. If the parameters are observed to lie in this special range, particle physics will establish that the future of our Universe is a global big crunch, without harboring pockets of eternal inflation, strongly suggesting that eternal inflation is censored by the fundamental theory. This conclusion could be drawn even more sharply if metastability with the appropriate decay rate is found in the MSSM, where the physics governing the instability can be directly probed at the TeV scale

New ATLAS Higgs physics results

CERN Multimedia

CERN. Geneva

2014-01-01

New Higgs physics results from the ATLAS experiment using the full Run-1 LHC dataset, corresponding to an integrated luminosity of approximately 25 fb-1, of proton-proton collisions at 7 TeV and 8 TeV, will be presented.

Top Quark and Higgs Boson Physics at LHC-ATLAS

Science.gov (United States)

Tomoto, M.

2013-03-01

One of the main goal of the Large Hadron Collider (LHC) experiments at CERN in Switzerland is to aim to solve the "origin of the mass" by discovering the Higgs boson and understanding the interaction of the Higgs boson with the elementary particles. The ATLAS, which is one of the LHC experiments has taken about 5 fb-1 of physics quality data and published several results with regard to the "origin of the mass" since March 2010. This presentation focuses on the latest results of the heaviest elementary particle, namely, top quark physics and the Higgs boson searches from ATLAS.

Higgs Working Group Report of the Snowmass 2013 Community Planning Study

CERN Document Server

Dawson, S; Logan, H; Qian, J; Tully, C; Van Kooten, R; Ajaib, A; Anastassov, A; Anderson, I; Bake, O; Barger, V; Barklow, T; Batell, B; Battaglia, M; Berge, S; Blondel, A; Bolognesi, S; Brau, J; Brownson, E; Cahill-Rowley, M; Calancha-Paredes, C; Chen, C -Y; Chou, W; Clare, R; Cline, D; Craig, N; Cranmer, K; de Gruttola, M; Elagin, A; Essig, R; Everett, L; Feng, E; Fujii, K; Gainer, J; Gao, Y; Gogoladze, I; Gori, S; Goncalo, R; Graf, N; Grojean, C; Guindon, S; Han, T; Hanson, G; Harnik, R; Heinemann, B; Heinemeyer, S; Heintz, U; Hewett, J; Ilchenko, Y; Ismail, A; Jain, V; Janot, P; Kawada, S; Kehoe, R; Klute, M; Kotwal, A; Krueger, K; Kukartsev, G; Kumar, K; Kunkle, J; Lewis, I; Li, Y; Linssen, L; Lipeles, E; Lipton, R; Liss, T; List, J; Liu, T; Liu, Z; Low, I; Ma, T; Mackenzie, P; Mellado, B; Melnikov, K; Moortgat-Pick, G; Mourou, G; Narain, M; Nielsen, J; Okada, N; Okawa, H; Olsen, J; Onyisi, P; Parashar, N; Peskin, M; Petriello, F; Plehn, T; Pollard, C; Potter, C; Prokofiev, K; Rauch, M; Rizzo, T; Robens, T; Rodriguez, V; Roloff, P; Ruiz, R; Sanz, V; Sayre, J; Shafi, Q; Shaughnessy, G; Sher, M; Simon, F; Solyak, N; Stupak, J; Su, S; Tanabe, T; Tajima, T; Telnov, V; Tian, J; Thomas, S; Thomson, M; Un, C; Velasco, M; Wagner, C; Wang, S; Whitbeck, A; Yao, W; Yokoya, H; Zenz, S; Zerwas, D; Zhang, Y; Zhou, Y

2013-01-01

This report summarizes the work of the Energy Frontier Higgs Boson working group of the 2013 Community Summer Study (Snowmass). We identify the key elements of a precision Higgs physics program and document the physics potential of future experimental facilities as elucidated during the Snowmass study. We study Higgs couplings to gauge boson and fermion pairs, double Higgs production for the Higgs self-coupling, its quantum numbers and $C\\!P$-mixing in Higgs couplings, the Higgs mass and total width, and prospects for direct searches for additional Higgs bosons in extensions of the Standard Model. Our report includes projections of measurement capabilities from detailed studies of the Compact Linear Collider (CLIC), a Gamma-Gamma Collider, the International Linear Collider (ILC), the Large Hadron Collider High-Luminosity Upgrade (HL-LHC), Very Large Hadron Colliders up to 100 TeV (VLHC), a Muon Collider, and a Triple-Large Electron Positron Collider (TLEP).

Higgs properties and decays, searches for high mass Higgs boson and di-Higgs production

CERN Document Server

Cadamuro, Luca

2018-01-01

The study of the scalar sector of the standard model of particle physics is one of the main goals of the LHC physics programme.A precise characterisation of the Higgs boson, searches for extensions of the scalar sector, and the study of Higgs boson pair production are complementary in this exploration.This document describes the status of Higgs boson physics analyses performed by the ATLAS and CMS Collaborations, focusing on the latest results from pp collisions at sqrt(s) = 13 TeV recorded in 2016, for an integrated luminosity of about 36 fb-1.

Higgs and new physics at high energy

International Nuclear Information System (INIS)

Solans, C.A.

2014-07-01

The observation of a new particle in the search for the Standard Model (SM) Higgs boson at the LHC, reported by the ATLAS and CMS collaborations, is a milestone in the quest to understand electroweak symmetry breaking. The evidence at the level of 5*σ for a Higgs boson-like particle has been published by both experiments after a preliminary analysis of the data from the LHC Run-I. Precision measurements of the new particle are of critical importance. ATLAS and CMS discovered a Higgs like particle with a mass close to 125.5 GeV, and measured the spin, parity and signal strength to be compatible with the one from the SM Higgs boson [J P = 0 + , μ(VBF+VH)=μ(ggH+ttH)=1]. In a coupling scale factors analysis, compatibility with the SM is found in all the tests performed, with probabilities ranging from 7% to 21%. Consequently, the Higgs physics potential of the LHC Run-I is almost exploited. Run-II and beyond will give the possibility to measure the couplings more precisely, to constrain rare decays further, and to determine a possible CP admixture of the Higgs boson

Higgs physics with hadronic signatures at ATLAS and CMS

CERN Document Server

Schroder, Matthias

2018-01-01

Precise measurement of the properties of the Higgs boson is of paramount interest in order to verify the standard model nature of the Higgs sector or discover new physics. Crucial information is obtained from investigation of hadronic final states, which offer, for example, a direct probe of the couplings to top or bottom quarks. In this article, latest results of Higgs boson measurements with hadronic signatures by ATLAS and CMS at the LHC are reviewed.

Prospects for Higgs physics at energies up to 100 TeV.

Science.gov (United States)

Baglio, Julien; Djouadi, Abdelhak; Quevillon, Jérémie

2016-11-01

We summarize the prospects for Higgs boson physics at future proton-proton colliders with centre of mass (c.m.) energies up to 100 TeV. We first provide the production cross sections for the Higgs boson of the Standard Model from 13 TeV to 100 TeV, in the main production mechanisms and in subleading but important ones such as double Higgs production, triple production and associated production with two gauge bosons or with a single top quark. We then discuss the production of Higgs particles in beyond the Standard Model scenarios, starting with the one in the continuum of a pair of scalar, fermionic and vector dark matter particles in Higgs-portal models in various channels with virtual Higgs exchange. The cross sections for the production of the heavier CP-even and CP-odd neutral Higgs states and the charged Higgs states in two-Higgs doublet models, with a specific study of the case of the Minimal Supersymmetric Standard Model, are then given. The sensitivity of a 100 TeV proton machine to probe the new Higgs states is discussed and compared to that of the LHC with a c.m. energy of 14 TeV and at high luminosity.

Beyond The Standard Model Higgs Physics with Photons with the CMS Detector

CERN Document Server

Teixeira de Lima, Rafael

The experimental discovery of the Higgs boson is one of the latest successes of the Standard Model of particle physics. Although all measurements have confirmed that this newly discovered particle is the Higgs boson predicted by the Standard Model, with no deviations to suggest otherwise, the Higgs boson can guide us to new models which modify the electroweak symmetry breaking mechanism or predict new states that couple to the Higgs. Therefore, it's paramount to directly look for modifications of our current model with the help of the recently discovered particle. In this thesis, two analyses involving beyond the Standard Model physics tied to the Higgs sector will be explored. First, looking at exotic Higgs decays, an analysis searching for the final state with photons and missing transverse energy will be presented. Then, the search for Higgs pair production, both resonantly and non-resonantly (a process predicted by the Standard Model, albeit at very low rates), in the final state with two bottom quark je...

Overview of the Higgs and Standard Model physics at ATLAS

CERN Document Server

Vazquez Schroeder, Tamara; The ATLAS collaboration

2018-01-01

This talk presents selected aspects of recent physics results from the ATLAS collaboration in the Standard Model and Higgs sectors, with a focus on the recent evidence for the associated production of the Higgs boson and a top quark pair.

A model of neutrino and Higgs physics at the electroweak scale

International Nuclear Information System (INIS)

Aranda, Alfredo; Blanno, Omar; Diaz-Cruz, J. Lorenzo

2008-01-01

We present and explore the Higgs physics of a model that in addition to the Standard Model fields includes a lepton number violating singlet scalar field. Based on the fact that the only experimental data we have so far for physics beyond the Standard Model is that of neutrino physics, we impose a constraint for any addition not to introduce new higher scales. As such, we introduce right-handed neutrinos with an electroweak scale mass. We study the Higgs decay H→νν and show that it leads to different signatures compared to those in the Standard Model, making it possible to detect them and to probe the nature of their couplings

A Ball Pool Model to Illustrate Higgs Physics to the Public

Science.gov (United States)

Organtini, Giovanni

2017-01-01

A simple model is presented to explain Higgs boson physics to the grand public. The model consists of a children's ball pool representing a Universe filled with a certain amount of the Higgs field. The model is suitable for usage as a hands-on tool in scientific exhibits and provides a clear explanation of almost all the aspects of the physics of…

Light-quarks Yukawa couplings and new physics in exclusive high-pT Higgs boson +jet and Higgs boson + b -jet events

Science.gov (United States)

Cohen, Jonathan; Bar-Shalom, Shaouly; Eilam, Gad; Soni, Amarjit

2018-03-01

We suggest that the exclusive Higgs +light (or b)-jet production at the LHC, p p →h +j (jb), is a rather sensitive probe of the light-quarks Yukawa couplings and of other forms of new physics (NP) in the Higgs-gluon h g g and quark-gluon q q g interactions. We study the Higgs pT-distribution in p p →h +j (jb)→γ γ +j (jb), i.e., in h +j (jb) production followed by the Higgs decay h →γ γ , employing the (pT-dependent) signal strength formalism to probe various types of NP which are relevant to these processes and which we parametrize either as scaled Standard Model (SM) couplings (the kappa-framework) and/or through new higher dimensional effective operators (the SMEFT framework). We find that the exclusive h +j (jb) production at the 13 TeV LHC is sensitive to various NP scenarios, with typical scales ranging from a few TeV to O (10 ) TeV , depending on the flavor, chirality and Lorentz structure of the underlying physics.

Lectures on Higgs Boson Physics in the Standard Model and Beyond

CERN Document Server

Wells, James D

2009-01-01

These lectures focus on the structure of various Higgs boson theories. Topics in the first lectures include: mass generation in chiral theories, spontaneous symmetry breaking, neutrino masses, perturbative unitarity, vacuum stability, vacuum alignment, flavor changing neutral current solutions with multiple Higgs doublets, analysis of type I theory with Z2 symmetry, and rephasing symmetries. After an Essay on the Hierarchy Problem, additional topics are covered that more directly relate to naturalness of the electroweak theory. Emphasis is on their connection to Higgs boson physics. Topics in these later lectures include: supersymmetry, supersymmetric Higgs sector in the Runge basis, leading-order radiative corrections of supersymmetric light Higgs boson mass, theories of extra dimensions, and radion mixing with the Higgs boson in warped extra dimensions. And finally, one lecture is devoted to Higgs boson connections to the hidden sector.

Higgs inflation, seesaw physics and fermion dark matter

Directory of Open Access Journals (Sweden)

Nobuchika Okada

2015-07-01

Full Text Available We present an inflationary model in which the Standard Model Higgs doublet field with non-minimal coupling to gravity drives inflation, and the effective Higgs potential is stabilized by new physics which includes a dark matter particle and right-handed neutrinos for the seesaw mechanism. All of the new particles are fermions, so that the Higgs doublet is the unique inflaton candidate. With central values for the masses of the top quark and the Higgs boson, the renormalization group improved Higgs potential is employed to yield the scalar spectral index ns≃0.968, the tensor-to-scalar ratio r≃0.003, and the running of the spectral index α=dns/dln⁡k≃−5.2×10−4 for the number of e-folds N0=60 (ns≃0.962, r≃0.004, and α≃−7.5×10−4 for N0=50. The fairly low value of r≃0.003 predicted in this class of models means that the ongoing space and land based experiments are not expected to observe gravity waves generated during inflation.

Linear Collider Physics Resource Book for Snowmass 2001, 2 Higgs and Supersymmetry Studies

CERN Document Server

Abe, T.; Asner, David Mark; Baer, H.; Bagger, Jonathan A.; Balazs, Csaba; Baltay, C.; Barker, T.; Barklow, T.; Barron, J.; Baur, Ulrich J.; Beach, R.; Bellwied, R.; Bigi, Ikaros I.Y.; Blochinger, C.; Boege, S.; Bolton, T.; Bower, G.; Brau, James E.; Breidenbach, Martin; Brodsky, Stanley J.; Burke, David L.; Burrows, Philip N.; Butler, Joel N.; Chakraborty, Dhiman; Cheng, Hsin-Chia; Chertok, Maxwell Benjamin; Choi, Seong-Youl; Cinabro, David; Corcella, Gennaro; Cordero, R.K.; Danielson, N.; Davoudiasl, Hooman; Dawson, S.; Denner, Ansgar; Derwent, P.; Diaz, Marco Aurelio; Dima, M.; Dittmaier, Stefan; Dixit, M.; Dixon, Lance J.; Dobrescu, Bogdan A.; Doncheski, M.A.; Duckwitz, M.; Dunn, J.; Early, J.; Erler, Jens; Feng, Jonathan L.; Ferretti, C.; Fisk, H.Eugene; Fraas, H.; Freitas, A.; Frey, R.; Gerdes, David W.; Gibbons, L.; Godbole, R.; Godfrey, S.; Goodman, E.; Gopalakrishna, Shrihari; Graf, N.; Grannis, Paul D.; Gronberg, Jeffrey Baton; Gunion, John F.; Haber, Howard E.; Han, Tao; Hawkings, Richard; Hearty, Christopher; Heinemeyer, Sven; Hertzbach, Stanley S.; Heusch, Clemens A.; Hewett, JoAnne L.; Hikasa, K.; Hiller, G.; Hoang, Andre H.; Hollebeek, Robert; Iwasaki, M.; Jacobsen, Robert Gibbs; Jaros, John Alan; Juste, A.; Kadyk, John A.; Kalinowski, J.; Kalyniak, P.; Kamon, Teruki; Karlen, Dean; Keller, L; Koltick, D.; Kribs, Graham D.; Kronfeld, Andreas Samuel; Leike, A.; Logan, Heather E.; Lykken, Joseph D.; Macesanu, Cosmin; Magill, Stephen R.; Marciano, William Joseph; Markiewicz, Thomas W.; Martin, S.; Maruyama, T.; Matchev, Konstantin Tzvetanov; Monig, Klaus; Montgomery, Hugh E.; Moortgat-Pick, Gudrid A.; Moreau, G.; Mrenna, Stephen; Murakami, Brandon; Murayama, Hitoshi; Nauenberg, Uriel; Neal, H.; Newman, B.; Nojiri, Mihoko M.; Orr, Lynne H.; Paige, F.; Para, A.; Pathak, S.; Peskin, Michael E.; Plehn, Tilman; Porter, F.; Potter, C.; Prescott, C.; Rainwater, David Landry; Raubenheimer, Tor O.; Repond, J.; Riles, Keith; Rizzo, Thomas Gerard; Ronan, Michael T.; Rosenberg, L.; Rosner, Jonathan L.; Roth, M.; Rowson, Peter C.; Schumm, Bruce Andrew; Seppala, L.; Seryi, Andrei; Siegrist, J.; Sinev, N.; Skulina, K.; Sterner, K.L.; Stewart, I.; Su, S.; Tata, Xerxes Ramyar; Telnov, Valery I.; Teubner, Thomas; Tkaczyk, S.; Turcot, Andre S.; van Bibber, Karl A.; Van Kooten, Rick J.; Vega, R.; Wackeroth, Doreen; Wagner, D.; Waite, Anthony P.; Walkowiak, Wolfgang; Weiglein, Georg; Wells, James Daniel; Wester, William Carl, III; Williams, B.; Wilson, G.; Wilson, R.; Winn, D.; Woods, M.; Wudka, J.; Yakovlev, Oleg I.; Yamamoto, H.; Yang, Hai Jun

2001-01-01

This Resource Book reviews the physics opportunities of a next-generation e+e- linear collider and discusses options for the experimental program. Part 2 reviews the possible experiments on Higgs bosons and supersymmetric particles that can be done at a linear collider.

Higgs boson events and background lep. A Monte Carlo study

International Nuclear Information System (INIS)

Ekspong, G.; Hultqvist, K.

1982-06-01

Higgs boson production at LEP using e+ e- to Z 0 to H 0 + e+ e- has been studied by Monte Carlo generation of events with realistic errors of measurement added. The results show the recoil mass (Higgs boson mass) resolution to be reasonably good for boson masses bigger than 5 Ge V. The events are found to populate a phase space region free of physical background for all boson masses below about 35 GeV. For masses above 40 GeV the Higgs boson signal merges with the physical background produced by semileptonic decays of heavy flavour quarks while diminishing in strength to low levels. The geometrical acceptance of a detector like DELPHI is about 80 per cent for Higgs boson events. (Author)

Working Group Report: Higgs Boson

Energy Technology Data Exchange (ETDEWEB)

Dawson, Sally; Gritsan, Andrei; Logan, Heather; Qian, Jianming; Tully, Chris; Van Kooten, Rick [et al.

2013-10-30

This report summarizes the work of the Energy Frontier Higgs Boson working group of the 2013 Community Summer Study (Snowmass). We identify the key elements of a precision Higgs physics program and document the physics potential of future experimental facilities as elucidated during the Snowmass study. We study Higgs couplings to gauge boson and fermion pairs, double Higgs production for the Higgs self-coupling, its quantum numbers and $CP$-mixing in Higgs couplings, the Higgs mass and total width, and prospects for direct searches for additional Higgs bosons in extensions of the Standard Model. Our report includes projections of measurement capabilities from detailed studies of the Compact Linear Collider (CLIC), a Gamma-Gamma Collider, the International Linear Collider (ILC), the Large Hadron Collider High-Luminosity Upgrade (HL-LHC), Very Large Hadron Colliders up to 100 TeV (VLHC), a Muon Collider, and a Triple-Large Electron Positron Collider (TLEP).

Review of Physics Results from the Tevatron: Higgs Boson Physics

International Nuclear Information System (INIS)

Junk, Thomas R.; Juste, Aurelio

2015-01-01

We review the techniques and results of the searches for the Higgs boson performed by the two Tevatron collaborations, CDF and DO. The Higgs boson predicted by the Standard Model was sought in the mass range 90 GeVHiggs boson with a mass in the range 115 GeVHiggs boson mass of m H =125 GeV, studies of Higgs boson properties were performed, including measurements of the product of the cross section times branching the ratio in various production and decay modes, constraints on Higgs boson couplings to fermions and vector bosons, and tests of spin and parity. We also summarize the results of searches for supersymmetric Higgs bosons, and Higgs bosons in other extensions of the Standard Model

Future ATLAS Higgs Studies

CERN Document Server

Smart, Ben; The ATLAS collaboration

2017-01-01

The High-Luminosity LHC will prove a challenging environment to work in, with for example $=200$ expected. It will however also provide great opportunities for advancing studies of the Higgs boson. The ATLAS detector will be upgraded, and Higgs prospects analyses have been performed to assess the reach of ATLAS Higgs studies in the HL-LHC era. These analyses are presented, as are Run-2 ATLAS di-Higgs analyses for comparison.

Studying Higgs pair production in the process γγ→H0H0 in the two-Higgs-doublet model

International Nuclear Information System (INIS)

La-Zhen, S.; Yao-Yang, L.

1996-01-01

In the two-Higgs-doublet model the complete nonstandard Higgs boson helicity amplitudes for the Higgs boson pair production process γγ→H 0 H 0 is calculated and explicit formulas for nonstandard Higgs boson contributions to the helicity amplitudes are given. It is shown that the cross section is in the range of 0.03 endash 30 pb at √s=1 TeV, for Higgs boson masses of 350 H 0 <490 GeV in monochromatic γγ collisions. The angular distribution for Higgs pair production is strongly peaked in the forward and backward directions. In particular the angular dependence for Higgs pair production is due to the nonstandard Higgs boson getting larger where the box diagrams constitute the dominant part of the differential cross section. For studying heavy Higgs pair production the use of circularly polarized photon beams with equal helicities is advantageous. copyright 1996 The American Physical Society

Impact of flavor and Higgs physics on theories beyond the standard model

Energy Technology Data Exchange (ETDEWEB)

Casagrande, Sandro

2013-02-13

Quantum effects of physics beyond the Standard Model receive strong indirect constraints from precisely measured collider observables. In the conceptual part of this thesis, we apply the generic relations between particle interactions in perturbatively unitary theories to calculate one-loop amplitudes for flavor physics. We provide template results applicable for any model of this class. We also investigate example models that are partly and such that are not perturbatively unitary: the Littlest Higgs model and Randall-Sundrum models. The latter have a unique coupling structure, which we cover exhaustively. We find strong constraints on the Randall-Sundrum models and numerically compare those from flavor, electroweak precision, and Higgs physics by performing detailed parameter scans. We observe interesting correlations between flavor observables, and we find that constraints from Higgs production and decays are already competitive.

Impact of flavor and Higgs physics on theories beyond the standard model

International Nuclear Information System (INIS)

Casagrande, Sandro

2013-01-01

Quantum effects of physics beyond the Standard Model receive strong indirect constraints from precisely measured collider observables. In the conceptual part of this thesis, we apply the generic relations between particle interactions in perturbatively unitary theories to calculate one-loop amplitudes for flavor physics. We provide template results applicable for any model of this class. We also investigate example models that are partly and such that are not perturbatively unitary: the Littlest Higgs model and Randall-Sundrum models. The latter have a unique coupling structure, which we cover exhaustively. We find strong constraints on the Randall-Sundrum models and numerically compare those from flavor, electroweak precision, and Higgs physics by performing detailed parameter scans. We observe interesting correlations between flavor observables, and we find that constraints from Higgs production and decays are already competitive.

Electroweak Higgs production with HiggsPO at NLO QCD

Science.gov (United States)

Greljo, Admir; Isidori, Gino; Lindert, Jonas M.; Marzocca, David; Zhang, Hantian

2017-12-01

We present the HiggsPO UFO model for Monte Carlo event generation of electroweak VH and VBF Higgs production processes at NLO in QCD in the formalism of Higgs pseudo-observables (PO). We illustrate the use of this tool by studying the QCD corrections, matched to a parton shower, for several benchmark points in the Higgs PO parameter space. We find that, while being sizable and thus important to be considered in realistic experimental analyses, the QCD higher-order corrections largely factorize. As an additional finding, based on the NLO results, we advocate to consider 2D distributions of the two-jet azimuthal-angle difference and the leading jet p_T for new physics searches in VBF Higgs production. The HiggsPO UFO model is publicly available.

Physical analysis of some features of the gauge theories with Higgs sectors

International Nuclear Information System (INIS)

Beshtoev, Kh.M.

1995-01-01

A physical analysis of some features of the gauge theories with Higgs sectors is made. It is shown that we should assume gauge transformations in the fermion and Higgs sectors to be different (i.e., to have different charges) in order to remove contradictions arising in gauge theories with Higgs sectors. Then, the Higgs mechanism can be interpreted as some mechanism of gauge field shielding. In such a mechanism fermions remain without masses. The conclusion is made that in the standard theory of the development of the Universe, monopoles cannot survive at low temperatures. 15 refs

Electroweak Higgs production with HiggsPO at NLO QCD

International Nuclear Information System (INIS)

Greljo, Admir; Isidori, Gino; Zhang, Hantian; Lindert, Jonas M.; Marzocca, David

2017-01-01

We present the HiggsPO UFO model for Monte Carlo event generation of electroweak VH and VBF Higgs production processes at NLO in QCD in the formalism of Higgs pseudo-observables (PO). We illustrate the use of this tool by studying the QCD corrections, matched to a parton shower, for several benchmark points in the Higgs PO parameter space. We find that, while being sizable and thus important to be considered in realistic experimental analyses, the QCD higher-order corrections largely factorize. As an additional finding, based on the NLO results, we advocate to consider 2D distributions of the two-jet azimuthal-angle difference and the leading jet p T for new physics searches in VBF Higgs production. The HiggsPO UFO model is publicly available. (orig.)

Electroweak Higgs production with HiggsPO at NLO QCD

Energy Technology Data Exchange (ETDEWEB)

Greljo, Admir [Universitaet Zuerich, Physik-Institut, Zurich (Switzerland); Johannes Gutenberg-Universitaet Mainz, PRISMA Cluster of Excellence and Mainz Institute for Theoretical Physics, Mainz (Germany); University of Sarajevo, Faculty of Science, Sarajevo (Bosnia and Herzegovina); Isidori, Gino; Zhang, Hantian [Universitaet Zuerich, Physik-Institut, Zurich (Switzerland); Lindert, Jonas M. [Durham University, Department of Physics, Institute for Particle Physics Phenomenology, Durham (United Kingdom); Marzocca, David [Universitaet Zuerich, Physik-Institut, Zurich (Switzerland); INFN, Sezione di Trieste(Italy); SISSA, Trieste (Italy)

2017-12-15

We present the HiggsPO UFO model for Monte Carlo event generation of electroweak VH and VBF Higgs production processes at NLO in QCD in the formalism of Higgs pseudo-observables (PO). We illustrate the use of this tool by studying the QCD corrections, matched to a parton shower, for several benchmark points in the Higgs PO parameter space. We find that, while being sizable and thus important to be considered in realistic experimental analyses, the QCD higher-order corrections largely factorize. As an additional finding, based on the NLO results, we advocate to consider 2D distributions of the two-jet azimuthal-angle difference and the leading jet p{sub T} for new physics searches in VBF Higgs production. The HiggsPO UFO model is publicly available. (orig.)

NLO qq -> ZH production and Effective Lagrangians for BSM Higgs Physics

CERN Document Server

Jomhari, Nur Zulaiha; CERN. Geneva. PH Department

2015-01-01

The naturalness issue is a compelling reason for the emergence of Beyond the Standard Model (BSM) physics at the Large Hadron Collider (LHC). Absence of hints in direct searches makes the model-independent Effective Field Theory (EFT) approach to Higgs physics interesting. It is important that to establish to which extent the new boson discovered at LHC is the scalar particle predicted by the SM. BSM physics can change the HZZ coupling that associated ZH production probes. Model-independent extensions of the SM can describe possible changes, described in a field-theoretical way, via an extended Lagrangian with the SM fields. In this project, Higgs boson is Attached to WeaK bosons (HAWK) and Madgraph5 are used as a Monte Carlo (MC) generator to distinguish higher-order SM corrections from actual BSM manifestations and this study attempts to address is whether one can “calibrate” EFT calculations to match the most accurate SM predictions.

Status of the charged Higgs boson in two Higgs doublet models

Science.gov (United States)

Arbey, A.; Mahmoudi, F.; Stål, O.; Stefaniak, T.

2018-03-01

The existence of charged Higgs boson(s) is inevitable in models with two (or more) Higgs doublets. Hence, their discovery would constitute unambiguous evidence for new physics beyond the Standard Model (SM). Taking into account all relevant results from direct charged and neutral Higgs boson searches at LEP and the LHC, as well as the most recent constraints from flavour physics, we present a detailed analysis of the current phenomenological status of the charged Higgs sector in a variety of well-motivated two Higgs doublet models (2HDMs). We find that charged Higgs bosons as light as 75 GeV can still be compatible with the combined data, although this implies severely suppressed charged Higgs couplings to all fermions. In more popular models, e.g. the 2HDM of Type II, we find that flavour physics observables impose a combined lower limit on the charged Higgs mass of M_{H^± } ≳ 600 GeV - independent of tan β - which increases to M_{H^± } ≳ 650 GeV for tan β < 1. We furthermore find that in certain scenarios, the signature of a charged Higgs boson decaying into a lighter neutral Higgs boson and a W boson provides a promising experimental avenue that would greatly complement the existing LHC search programme for charged Higgs boson(s).

Status of the charged Higgs boson in two Higgs doublet models

International Nuclear Information System (INIS)

Arbey, A.; Mahmoudi, F.; Stefaniak, T.; Staal, O.

2018-01-01

The existence of charged Higgs boson(s) is inevitable in models with two (or more) Higgs doublets. Hence, their discovery would constitute unambiguous evidence for new physics beyond the Standard Model (SM). Taking into account all relevant results from direct charged and neutral Higgs boson searches at LEP and the LHC, as well as the most recent constraints from flavour physics, we present a detailed analysis of the current phenomenological status of the charged Higgs sector in a variety of well-motivated two Higgs doublet models (2HDMs). We find that charged Higgs bosons as light as 75 GeV can still be compatible with the combined data, although this implies severely suppressed charged Higgs couplings to all fermions. In more popular models, e.g. the 2HDM of Type II, we find that flavour physics observables impose a combined lower limit on the charged Higgs mass of M H ± > or similar 600 GeV - independent of tan β - which increases to M H ± > or similar 650 GeV for tan β < 1. We furthermore find that in certain scenarios, the signature of a charged Higgs boson decaying into a lighter neutral Higgs boson and a W boson provides a promising experimental avenue that would greatly complement the existing LHC search programme for charged Higgs boson(s). (orig.)

Looking For Physics Beyond The Standard Model: Searches For Charged Higgs Bosons At $e^{+}e^{-}$ Colliders

CERN Document Server

Kiiskinen, A P

2004-01-01

This thesis describes direct searches for pair production of charged Higgs bosons performed in the data collected by the DELPHI detector at the LEP collider at CERN. In addition, the possibilities to discover and study heavy charged Higgs bosons at possible future high-energy linear colliders are presented. The existence of charged Higgs bosons is predicted by many extensions of the Standard Model. A possible discovery of these particles would be a solid proof for physics beyond the Standard Model. Discovery of charged Higgs bosons, and measurement of their properties, would also provide useful information about the structure of the more general theory. New analysis methods were developed for the searches performed at LEP. A large, previously unexplored, mass range for cover but no evidence for the existence of the charged Higgs bosons was found. This allowed setting new lower mass limits for the charged Higgs boson within the framework of general two Higgs doublet models. Results have been interpreted and pr...

Simplified models for Higgs physics: singlet scalar and vector-like quark phenomenology

Energy Technology Data Exchange (ETDEWEB)

Dolan, Matthew J. [ARC Centre of Excellence for Particle Physics at the Terascale,School of Physics, University of Melbourne,Melbourne 3010 (Australia); Hewett, J.L. [SLAC National Accelerator Laboratory,Menlo Park 94025, CA (United States); Krämer, M. [Institute for Theoretical Particle Physics and Cosmology, RWTH Aachen University,D-52056 Aachen (Germany); Rizzo, T.G. [SLAC National Accelerator Laboratory,Menlo Park 94025, CA (United States)

2016-07-08

Simplified models provide a useful tool to conduct the search and exploration of physics beyond the Standard Model in a model-independent fashion. In this work we consider the complementarity of indirect searches for new physics in Higgs couplings and distributions with direct searches for new particles, using a simplified model which includes a new singlet scalar resonance and vector-like fermions that can mix with the SM top-quark. We fit this model to the combined ATLAS and CMS 125 GeV Higgs production and coupling measurements and other precision electroweak constraints, and explore in detail the effects of the new matter content upon Higgs production and kinematics. We highlight some novel features and decay modes of the top partner phenomenology, and discuss prospects for Run II.

Perturbative calculations and their application to Higgs physics

International Nuclear Information System (INIS)

Zirke, Tom J.E.

2014-09-01

In this thesis the numerical calculation of IR-finite two-loop integrals for processes related to Higgs physics in four-dimensional regularization regarding especilla the process gg→HZ is described. An application to two-loop vacuum integrals with φ→γγ at NLO QCD is presented. (HSI)

New Physics and novel Higgs signals

International Nuclear Information System (INIS)

Diaz-Cruz, J. Lorenzo

2003-01-01

We review some of the results of our recent work dealing with the novel type of Higgs signals that arise when one considers extensions of the standard model. We discuss first possible deviations on the Higgs couplings due to heavy particles, in the context of the MSSM and with large extra-dimensions. Then, we present several models where it is possible to induce flavor violating Higgs couplings, and probe them at future hadron colliders through the LFV Higgs decay h → τμ or with rare top decays

Search of New Physics with Boosted Higgs Boson in Hadronic Final States with ATLAS Detector

CERN Document Server

AUTHOR|(INSPIRE)INSPIRE-00387563

The discovery of a Higgs boson at the Large Hadron Collider (LHC) confirms the validity of the Standard Model (SM) in the description of particle interactions at electroweak scale. However, radioactive corrections to the Higgs mass drives its value to the model's validity limit, indicating either extreme fine-tuning or the presence of new physics at higher energy scale. Since 2015, the LHC starts its Run 2 journey with unprecedented center of mass energy of 13 TeV. Along with increase in luminosity, this greatly extends the sensitivity of ATLAS experiment to heavy new particles at TeV scale. In particular, many new physics models beyond the Standard Model manifest themselves through significant coupling to the Higgs boson in decays of new particles to a Higgs boson and other SM particles. In this work, two searches for resonances decaying to either pair of Higgs bosons or a Higgs boson associated with another SM vector boson in all hadronic final states are presented using data collected by ATLAS during Run 2...

Higgs Particle: The Origin of Mass

Science.gov (United States)

Okada, Yasuhiro

2007-11-01

The Higgs particle is a new elementary particle predicted in the Standard Model of the elementary particle physics. It plays a special role in the theory of mass generation of quarks, leptons, and gauge bosons. In this article, theoretical issues on the Higgs mechanism are first discussed, and then experimental prospects on the Higgs particle study at the future collider experiments, LHC and ILC, are reviewed. The Higgs coupling determination is an essential step to establish the mass generation mechanism, which could lead to a deeper understanding of particle physics.

Higgs particle. The origin of mass

International Nuclear Information System (INIS)

Okada, Yasuhiro

2007-01-01

The Higgs particle is a new elementary particle predicted in the Standard Model of the elementary particle physics. It plays a special role in the theory of mass generation of quarks, leptons, and gauge bosons. In this article, theoretical issues on the Higgs mechanism are first discussed, and then experimental prospects on the Higgs particle study at the future collider experiments. LHC and ILC, are reviewed. The Higgs coupling determination is an essential step to establish the mass generation mechanism, which could lead to a deeper understanding of particle physics. (author)

A Study Of Observability Of Higgs Boson Decay In Higgs Boson Decays To Two Z Mesons Decays To Four Leptons At Cms

CERN Document Server

Liang, G

2005-01-01

The Standard Model (SM) of particle physics has been the most successful theory about fundamental particles and how they interact. In SM, the originally massless fundamental particles acquire masses in a process called the Higgs mechanism. This mechanism involves an additional particle, called the Higgs boson, whose responsibility is to break the electroweak symmetry and help those massless particles acquire masses. With the discovery of the top quark at Tevatron in 1995, the Higgs boson remains to be the only unfound fundamental particle in the Standard Model. The discovery of the Higgs boson would greatly increase our understanding of the origin of the mass. One of the most important objectives of the LHC experiment is to discover the Higgs boson. At LHC, the CMS experiment is optimized for the search of the Higgs boson over a mass range up to 1 TeV. Among all Higgs decay channels, H → ZZ → 4l is one of the most promising channels to search the SM Higgs boson at CMS. This study concentrat...

ATLAS Higgs and Supersymmetry Physics Prospects at the High-Luminosity LHC

CERN Document Server

AUTHOR|(INSPIRE)INSPIRE-00225111; The ATLAS collaboration

2018-01-01

The Higgs physics prospects at the high-luminosity LHC are presented, assuming an energy of sqrt(s) = 14 TeV and a data sample of 3000-4000 fb-1. In particular, the ultimate precision attainable on the couplings measurements of the 125 GeV Higgs boson with SM fermions and bosons is discussed, as well as perspectives on the search for the Standard Model di-Higgs production, which could lead to the measurement of the Higgs boson self-coupling. Scenarios of SUSY sparticle production, among others, have been used as benchmark to drive the design of the component upgrades, and to evaluate the sensitivity of the upgraded accelerator and detector. This talk will also overview the expected sensitivity that the ATLAS experiment will have to SUSY sparticle production with 3000 fb-1 pf proton-proton collisions collected at a centre of mass energy of 14 TeV.

Top quark and Higgs boson masses: Interplay between infared and ultraviolet physics

International Nuclear Information System (INIS)

Schrempp, B.; Wimmer, M.

1996-05-01

We review recent efforts to explore the information on masses of heavy matter particles, notable of the top quark and the Higgs boson, as encoded at the quantum level in the renormalization group equations. The standard model (SM) and the minimal supersymmetric standard model (MSSM) are considered in parallel throughout. First, the question is addressed to which extent the infrared physics of the ''top-down'' renormalization group flow is independent of the ultraviolet physics. The central issues are (i) infrared attractive fixed point values for the top and the Higgs mass, the most outstanding one being m t =O (190 GeV) sin β in the MSSM, (ii) infrared attractive relations between parameters, the most prominent ones being an infrared fixed top-Higgs mass relation in the SM, leading to m H =O (156 GeV) for the experimental top mass, and an infrared fixed relation between the top mass and the parameter tan β in the MSSM, and (iii) a systematical analytical assessment of their respective strengths of attraction. The triviality and vacuum stability bounds on the Higgs and top masses in the SM as well as the upper bound on the mass of the lightest Higgs boson in the MSSM are reviewed. The mathematical backbone for all these features, the rich structure of infrared attractive fixed points, lines, surfaces,.. in the corresponding multiparameter space, is made transparent

High performance computing system in the framework of the Higgs boson studies

CERN Document Server

Belyaev, Nikita; The ATLAS collaboration

2017-01-01

The Higgs boson physics is one of the most important and promising fields of study in modern High Energy Physics. To perform precision measurements of the Higgs boson properties, the use of fast and efficient instruments of Monte Carlo event simulation is required. Due to the increasing amount of data and to the growing complexity of the simulation software tools, the computing resources currently available for Monte Carlo simulation on the LHC GRID are not sufficient. One of the possibilities to address this shortfall of computing resources is the usage of institutes computer clusters, commercial computing resources and supercomputers. In this paper, a brief description of the Higgs boson physics, the Monte-Carlo generation and event simulation techniques are presented. A description of modern high performance computing systems and tests of their performance are also discussed. These studies have been performed on the Worldwide LHC Computing Grid and Kurchatov Institute Data Processing Center, including Tier...

Higgs Physics and Cosmology

Science.gov (United States)

Roberts, Alex

2016-08-01

Recently, a new framework for describing the multiverse has been proposed which is based on the principles of quantum mechanics. The framework allows for well-defined predictions, both regarding global properties of the universe and outcomes of particular experiments, according to a single probability formula. This provides complete unification of the eternally inflating multiverse and many worlds in quantum mechanics. We elucidate how cosmological parameters can be calculated in this framework, and study the probability distribution for the value of the cosmological constant. We consider both positive and negative values, and find that the observed value is consistent with the calculated distribution at an order of magnitude level. In particular, in contrast to the case of earlier measure proposals, our framework prefers a positive cosmological constant over a negative one. These results depend only moderately on how we model galaxy formation and life evolution therein. We explore supersymmetric theories in which the Higgs mass is boosted by the non-decoupling D-terms of an extended U(1) X gauge symmetry, defined here to be a general linear combination of hypercharge, baryon number, and lepton number. Crucially, the gauge coupling, gX, is bounded from below to accommodate the Higgs mass, while the quarks and leptons are required by gauge invariance to carry non-zero charge under U(1)X. This induces an irreducible rate, sigmaBR, for pp → X → ll relevant to existing and future resonance searches, and gives rise to higher dimension operators that are stringently constrained by precision electroweak measurements. Combined, these bounds define a maximally allowed region in the space of observables, (sigmaBR, mX), outside of which is excluded by naturalness and experimental limits. If natural supersymmetry utilizes non-decoupling D-terms, then the associated X boson can only be observed within this window, providing a model independent 'litmus test' for this broad

Your Higgs number—how fundamental physics is connected to technology and societal revolutions

Science.gov (United States)

Allen, Roland E.; Lidström, Suzy

2015-02-01

Fundamental physics, as exemplified by the recently discovered Higgs boson, often appears to be completely disconnected from practical applications and ordinary human life. But this is not really the case, because science, technology, and human affairs are profoundly integrated in ways that are not immediately obvious. We illustrate this by defining a ‘Higgs number’ through overlapping activities. Following three different paths, which end respectively in applications of the World Wide Web, digital photography, and all modern electronic devices, we find that most people have a Higgs number of no greater than 3.

New physics effects in Higgs decay to tau leptons

International Nuclear Information System (INIS)

Mantry, Sonny; Ramsey-Musolf, Michael J.; Trott, Michael

2008-01-01

We study the possible effects of TeV scale new physics (NP) on the rate for Higgs boson decays to charged leptons, focusing on the τ + τ - channel which can be readily studied at the Large Hadron Collider. Using an SU(3) C xSU(2) L xU(1) Y invariant effective theory valid below a NP scale Λ, we determine all effective operators up to dimension six that could generate appreciable contributions to the decay rate and compute the dependence of the rate on the corresponding operator coefficients. We bound the size of these operator coefficients based on the scale of the τ mass, naturalness considerations, and experimental constraints on the τ anomalous magnetic moment. These considerations imply that contributions to the decay rate, when Λ∼TeV, could be comparable to the prediction based on the SM Yukawa interaction. A reliable test of the Higgs mechanism for fermion mass generation via the h→τ + τ - channel is possible only after such NP effects are understood and brought under theoretical control

Higgs physics at the LHC

CERN Document Server

Mariotti, Chiara

2017-01-01

The first measurements of the mass, the width, and the couplings of the newly discovered Higgs boson at LHC at 7 and 8 TeV center of mass energy will be reviewed. Recent results at 13 TeV center of mass energy will be presented. Finally, searches for additional Higgs bosons in models beyond the standard model will be summarised.

Higgs couplings: disentangling new physics with off-shell measurements.

Science.gov (United States)

Cacciapaglia, Giacomo; Deandrea, Aldo; La Rochelle, Guillaume Drieu; Flament, Jean-Baptiste

2014-11-14

After the discovery of a scalar resonance, resembling the Higgs boson, its couplings have been extensively studied via the measurement of various production and decay channels on the invariant mass peak. Recently, the possibility of using off-shell measurements has been suggested: in particular, the CMS Collaboration has published results based on the high-invariant mass cross section of the process gg→ZZ, which contains a contribution from the Higgs boson. While this measurement has been interpreted as a constraint on the Higgs width after very specific assumptions are taken on the Higgs couplings, in this Letter, we show that a much more model-independent interpretation is possible.

Higgs physics at the Large Hadron Collider

Indian Academy of Sciences (India)

Higgs boson; Large Hadron Collider; electroweak symmetry; spin and CP of the Higgs boson ... I shall then give a short description of the pre-LHC constraints on the Higgs mass and the theoretical predictions for the LHC along with a discussion of the current experimental results, ending with prospects in the near future at ...

Higgs cosmology

Science.gov (United States)

Rajantie, Arttu

2018-01-01

The discovery of the Higgs boson in 2012 and other results from the Large Hadron Collider have confirmed the standard model of particle physics as the correct theory of elementary particles and their interactions up to energies of several TeV. Remarkably, the theory may even remain valid all the way to the Planck scale of quantum gravity, and therefore it provides a solid theoretical basis for describing the early Universe. Furthermore, the Higgs field itself has unique properties that may have allowed it to play a central role in the evolution of the Universe, from inflation to cosmological phase transitions and the origin of both baryonic and dark matter, and possibly to determine its ultimate fate through the electroweak vacuum instability. These connections between particle physics and cosmology have given rise to a new and growing field of Higgs cosmology, which promises to shed new light on some of the most puzzling questions about the Universe as new data from particle physics experiments and cosmological observations become available. This article is part of the Theo Murphy meeting issue `Higgs cosmology'.

Review of searches for Higgs bosons and beyond the standard model physics at the Tevatron

International Nuclear Information System (INIS)

Duperrin, Arnaud

2009-01-01

The energy frontier is currently at the Fermilab Tevatron accelerator, which collides protons and antiprotons at a center-of-mass energy of 1.96 TeV. The luminosity delivered to the CDF and DOe experiments has now surpassed the 4 fb -1 . This paper reviews the most recent direct searches for Higgs bosons and beyond-the-standard-model (BSM) physics at the tevatron. The results reported correspond to an integrated luminosity of up to 2.5 fb -1 of Run II data collected by the two Collaborations. Searches covered include the standard model (SM) Higgs boson (including sensitivity projections), the neutral Higgs bosons in the minimal supersymmetric extension of the standard model (MSSM), charged Higgs bosons and extended Higgs models, supersymmetric decays that conserve or violate R-parity, gauge-mediated supersymmetric breaking models, long-lived particles, leptoquarks, compositeness, extra gauge bosons, extra dimensions, and finally signature-based searches. Given the excellent performance of the collider and the continued productivity of the experiments, the Tevatron physics potential looks promising for discovery with the coming larger data sets. In particular, evidence for the SM Higgs boson could be obtained if its mass is light or near 160 GeV. The observed (expected) upper limits are currently a factor of 3.7 (3.3) higher than the expected SM Higgs boson cross section at m H =115 GeV and 1.1(1.6) at m H =160 GeV at 95% C.L. (orig.)

Heavy Higgs searches. Flavour matters

International Nuclear Information System (INIS)

Gori, Stefania; Paul, Ayan

2017-10-01

We point out that the stringent lower bounds on the masses of additional electrically neutral and charged Higgs bosons crucially depend on the flavour structure of their Yukawa interactions. We show that these bounds can easily be evaded by the introduction of flavour-changing neutral currents in the Higgs sector. As an illustration, we study the phenomenology of a two Higgs doublet model with a Yukawa texture singling out the third family of quarks and leptons. We combine constraints from low-energy flavour physics measurements, LHC measurements of the 125 GeV Higgs boson rates, and LHC searches for new heavy Higgs bosons. We propose novel LHC searches that could be performed in the coming years to unravel the existence of these new Higgs bosons.

Heavy Higgs searches. Flavour matters

Energy Technology Data Exchange (ETDEWEB)

Gori, Stefania [Cincinnati Univ., OH (United States). Dept. of Physics; Grojean, Christophe [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Juste, Aurelio [Institut de Fisica d' Altes Energies (IFAE), Barcelona (Spain); Institucio Catalanade Recerca i Estudis Avancats (ICREA), Barcelona (Spain); Paul, Ayan [INFN, Sezione di Roma (Italy)

2017-10-15

We point out that the stringent lower bounds on the masses of additional electrically neutral and charged Higgs bosons crucially depend on the flavour structure of their Yukawa interactions. We show that these bounds can easily be evaded by the introduction of flavour-changing neutral currents in the Higgs sector. As an illustration, we study the phenomenology of a two Higgs doublet model with a Yukawa texture singling out the third family of quarks and leptons. We combine constraints from low-energy flavour physics measurements, LHC measurements of the 125 GeV Higgs boson rates, and LHC searches for new heavy Higgs bosons. We propose novel LHC searches that could be performed in the coming years to unravel the existence of these new Higgs bosons.

Higgs Particle: The Origin of Mass

OpenAIRE

Okada, Yasuhiro

2007-01-01

The Higgs particle is a new elementary particle predicted in the Standard Model of the elementary particle physics. It plays a special role in the theory of mass generation of quarks, leptons, and gauge bosons. In this article, theoretical issues on the Higgs mechanism are first discussed, and then experimental prospects on the Higgs particle study at the future collider experiments, LHC and ILC, are reviewed. The Higgs coupling determination is an essential step to establish the mass generat...

Boosted Higgs shapes

International Nuclear Information System (INIS)

Schlaffer, Matthias; Spannowsky, Michael; Wymant, Chris

2014-05-01

The inclusive Higgs production rate through gluon fusion has been measured to be in agreement with the Standard Model (SM). We show that even if the inclusive Higgs production rate is very SM-like, a precise determination of the boosted Higgs transverse momentum shape offers the opportunity to see effects of natural new physics. These measurements are generically motivated by effective field theory arguments and specifically in extensions of the SM with a natural weak scale, like composite Higgs models and natural supersymmetry. We show in detail how a measurement at high transverse momentum of H→2l+p T via H→ττ and H→WW * could be performed and demonstrate that it offers a compelling alternative to the t anti tH channel. We discuss the sensitivity to new physics in the most challenging scenario of an exactly SM-like inclusive Higgs cross-section.

Particle physics after the Higgs discovery: Philosophical perspectives

Science.gov (United States)

Friederich, Simon; Lehmkuhl, Dennis

2015-08-01

The recent discovery at the LHC of a particle with properties matching those expected of the Higgs boson is a decisive event in the history of particle physics. The present special section combines three contributions that approach conceptual and methodological challenges related to this event and the current situation in particle physics from different angles. One contribution studies the experimental practices of contemporary particle physics by investigating the role of computer simulations in these practices; in particular, it focuses on the status of simulations as compared to experiments that in some circumstances have analogous functions. One contribution investigates the status of the controversial naturalness problem that many physicists see as the most severe shortcoming of the Standard Model of elementary particle physics. Finally, a third contribution critically assesses the impact of suggested no-go theorems concerning the interpretability of rigorous algebraic quantum field theory in terms of particles at the phenomenological level. In what follows we present a short overview of these contributions, highlighting some of their central ideas and arguments and putting them into context.

The Higgs hunter's guide

CERN Document Server

Gunion, John F; Haber, Howard E; Kane, Gordon L

1989-01-01

The Higgs Hunter's Guide is a definitive and comprehensive guide to the physics of Higgs bosons. In particular, it discusses the extended Higgs sectors required by those recent theoretical approaches that go beyond the Standard Model, including supersymmetry and superstring-inspired models.

Phenomenology of the Higgs effective Lagrangian via FEYNRULES

International Nuclear Information System (INIS)

Alloul, Adam; Fuks, Benjamin; Sanz, Verónica

2014-01-01

The Higgs discovery and the lack of any other hint for new physics favor a description of non-standard Higgs physics in terms of an effective field theory. We present an implementation of a general Higgs effective Lagrangian containing operators up to dimension six in the framework of FEYNRULES and provide details on the translation between the mass and interaction bases, in particular for three- and four-point interaction vertices involving Higgs and gauge bosons. We illustrate the strengths of this implementation by using the UFO interface of FEYNRULES capable to generate model files that can be understood by the MADGRAPH 5 event generator and that have the specificity to contain all interaction vertices, without any restriction on the number of external legs or on the complexity of the Lorentz structures. We then investigate several new physics effects in total rates and differential distributions for different Higgs production modes, including gluon fusion, associated production with a gauge boson and di-Higgs production. We finally study contact interactions of gauge and Higgs bosons to fermions

Phenomenology of the Higgs effective Lagrangian via FEYNRULES

Energy Technology Data Exchange (ETDEWEB)

Alloul, Adam [Groupe de Recherche de Physique des Hautes Énergies (GRPHE), Université de Haute-Alsace, IUT Colmar, 34 rue du Grillenbreit BP 50568, 68008 Colmar Cedex (France); Fuks, Benjamin [Theory Division, Physics Department, CERN, CH-1211 Geneva 23 (Switzerland); Institut Pluridisciplinaire Hubert Curien/Département Recherches Subatomiques,Université de Strasbourg/CNRS-IN2P3, 23 rue du Loess, F-67037 Strasbourg (France); Sanz, Verónica [Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH (United Kingdom)

2014-04-16

The Higgs discovery and the lack of any other hint for new physics favor a description of non-standard Higgs physics in terms of an effective field theory. We present an implementation of a general Higgs effective Lagrangian containing operators up to dimension six in the framework of FEYNRULES and provide details on the translation between the mass and interaction bases, in particular for three- and four-point interaction vertices involving Higgs and gauge bosons. We illustrate the strengths of this implementation by using the UFO interface of FEYNRULES capable to generate model files that can be understood by the MADGRAPH 5 event generator and that have the specificity to contain all interaction vertices, without any restriction on the number of external legs or on the complexity of the Lorentz structures. We then investigate several new physics effects in total rates and differential distributions for different Higgs production modes, including gluon fusion, associated production with a gauge boson and di-Higgs production. We finally study contact interactions of gauge and Higgs bosons to fermions.

Standard model Higgs physics at colliders

International Nuclear Information System (INIS)

Rosca, A.

2007-01-01

In this report we briefly review the experimental status and prospects to verify the Higgs mechanism of spontaneous symmetry breaking. The focus is on the most relevant aspects of the phenomenology of the Standard Model Higgs boson at current (Tevatron) and future (Large Hadron Collider, LHC and International Linear Collider, ILC) particle colliders. We review the Standard Model searches: searches at the Tevatron, the program planned at the LHC and prospects at the ILC. Emphasis is put on what follows after a candidate discovery at the LHC: the various measurements which are necessary to precisely determine what the properties of this Higgs candidate are. (author)

Beyond the Standard Model Higgs searches at the LHC

CERN Document Server

Meridiani, P

2015-01-01

The Run I at the LHC marks the birth of the "Higgs physics", a path which will be followed at its full extent in the future runs of the LHC. Indeed there are two complementary paths to be followed to new physics in the Higgs sector: precision measurements of the Higgs properties (couplings, mass, spin and parity), where new physics can manifest as deviation from the Standard Model, or direct search for processes not foreseen in the Standard Model (Higgs decays not foreseen in the Standard Model, additional scalars which would indicate an extended Higgs sector). The current status of these studies at the LHC is presented, focussing in particular on the direct searches for rare or invisible Higgs decays or for an extended Higgs sector. The results are based on the analysis of the proton-proton collisions at 7 and 8 TeV center-of-mass energy at the LHC by the ATLAS and CMS collaborations.

Higgs cosmology.

Science.gov (United States)

Rajantie, Arttu

2018-03-06

The discovery of the Higgs boson in 2012 and other results from the Large Hadron Collider have confirmed the standard model of particle physics as the correct theory of elementary particles and their interactions up to energies of several TeV. Remarkably, the theory may even remain valid all the way to the Planck scale of quantum gravity, and therefore it provides a solid theoretical basis for describing the early Universe. Furthermore, the Higgs field itself has unique properties that may have allowed it to play a central role in the evolution of the Universe, from inflation to cosmological phase transitions and the origin of both baryonic and dark matter, and possibly to determine its ultimate fate through the electroweak vacuum instability. These connections between particle physics and cosmology have given rise to a new and growing field of Higgs cosmology, which promises to shed new light on some of the most puzzling questions about the Universe as new data from particle physics experiments and cosmological observations become available.This article is part of the Theo Murphy meeting issue 'Higgs cosmology'. © 2018 The Author(s).

Handbook of LHC Higgs Cross Sections: 4. Deciphering the Nature of the Higgs Sector

Energy Technology Data Exchange (ETDEWEB)

de Florian, D. [National Univ. of San Martin, Buenos Aires (Argentina); et al.

2016-10-25

This Report summarizes the results of the activities of the LHC Higgs Cross Section Working Group in the period 2014-2016. The main goal of the working group was to present the state-of-the-art of Higgs physics at the LHC, integrating all new results that have appeared in the last few years. The first part compiles the most up-to-date predictions of Higgs boson production cross sections and decay branching ratios, parton distribution functions, and off-shell Higgs boson production and interference effects. The second part discusses the recent progress in Higgs effective field theory predictions, followed by the third part on pseudo-observables, simplified template cross section and fiducial cross section measurements, which give the baseline framework for Higgs boson property measurements. The fourth part deals with the beyond the Standard Model predictions of various benchmark scenarios of Minimal Supersymmetric Standard Model, extended scalar sector, Next-to-Minimal Supersymmetric Standard Model and exotic Higgs boson decays. This report follows three previous working-group reports: Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002), Handbook of LHC Higgs Cross Sections: 2. Differential Distributions (CERN-2012-002), and Handbook of LHC Higgs Cross Sections: 3. Higgs properties (CERN-2013-004). The current report serves as the baseline reference for Higgs physics in LHC Run 2 and beyond.

A tale of twin Higgs: natural twin two Higgs doublet models

International Nuclear Information System (INIS)

Yu, Jiang-Hao

2016-01-01

In original twin Higgs model, vacuum misalignment between electroweak and new physics scales is realized by adding explicit ℤ 2 breaking term. Introducing additional twin Higgs could accommodate spontaneous ℤ 2 breaking, which explains origin of this misalignment. We introduce a class of twin two Higgs doublet models with most general scalar potential, and discuss general conditions which trigger electroweak and ℤ 2 symmetry breaking. Various scenarios on realising the vacuum misalignment are systematically discussed in a natural composite two Higgs double model framework: explicit ℤ 2 breaking, radiative ℤ 2 breaking, tadpole-induced ℤ 2 breaking, and quartic-induced ℤ 2 breaking. We investigate the Higgs mass spectra and Higgs phenomenology in these scenarios.

7th Higgs Hunting 2016

CERN Document Server

2016-01-01

A subject of major importance in fundamental physics is the investigation of the origin of Electroweak Symmetry Breaking. The mechanism of mass generation through the spontaneous breaking of a gauge symmetry is called the Brout-Englert-Higgs mechanism and is associated with the appearance of a physical scalar boson. The discovery announced at CERN on 4th July 2012 by the ATLAS and CMS Collaborations of a boson at a mass close to 125 GeV/c2, compatible with this scalar boson of the Standard Model, the so-called Higgs boson, mainly in γγ, ZZ and WW decay modes, with compatible evidence also found at Fermilab in the bb mode, changed the landscape. This important discovery was acknowledged as decisive for the attribution of the 2013 Nobel Prize in Physics awarded jointly to François Englert and Peter Higgs . This 7th workshop of the "Higgs Hunting" series organized in Paris on August 31 - September 2, 2016 will discuss the developments of LHC run 2 analyses, detailed studies of the new boson and possible de...

Invisible Higgs decays from Higgs-graviscalar mixing

International Nuclear Information System (INIS)

Dominici, Daniele; Gunion, John F.

2009-01-01

We recompute the invisible Higgs decay width arising from Higgs-graviscalar mixing in the Arkani-Hamed, Dimopoulos, Dvali model, comparing the original derivation in the nondiagonal mass basis to that in a diagonal mass basis. The results obtained are identical (and differ by a factor of 2 from the original calculation) but the diagonal-basis derivation is pedagogically useful for clarifying the physics of the invisible width from mixing. We emphasize that both derivations make it clear that a direct scan in energy for a process such as WW→WW mediated by Higgs plus graviscalar intermediate resonances would follow a single Breit-Wigner form with total width given by Γ tot =Γ h SM +Γ invisible . We also compute the additional contributions to the invisible width due to direct Higgs to graviscalar-pair decays. We find that the invisible width due to the latter is relatively small, unless the Higgs mass is comparable to or larger than the effective extra-dimensional Planck mass.

The Higgs particle and higher-dimensional theories

International Nuclear Information System (INIS)

Lim, C. S.

2014-01-01

In spite of the great success of LHC experiments, we do not know whether the discovered “standard model-like” Higgs particle is really what the standard model predicts, or a particle that some new physics has in its low-energy effective theory. Also, the long-standing problems concerning the property of the Higgs and its interactions are still there, and we still do not have any conclusive argument on the origin of the Higgs itself. In this article we focus on higher-dimensional theories as new physics. First we give a brief review of their representative scenarios and closely related 4D scenarios. Among them, we mainly discuss two interesting possibilities of the origin of the Higgs: the Higgs as a gauge boson and the Higgs as a (pseudo) Nambu–Goldstone boson. Next, we argue that theories of new physics are divided into two categories, i.e., theories with normal Higgs interactions and those with anomalous Higgs interactions. Interestingly, both the candidates for the origin of the Higgs mentioned above predict characteristic “anomalous” Higgs interactions, such as the deviation of the Yukawa couplings from the standard model predictions. Such deviations can hopefully be investigated by precision tests of Higgs interactions at the planned ILC experiment. Also discussed is the main decay mode of the Higgs, H→γγ. Again, theories belonging to different categories are known to predict remarkably different new physics contributions to this important process

Constraining supersymmetric models using Higgs physics, precision observables and direct searches

International Nuclear Information System (INIS)

Zeune, Lisa

2014-08-01

We present various complementary possibilities to exploit experimental measurements in order to test and constrain supersymmetric (SUSY) models. Direct searches for SUSY particles have not resulted in any signal so far, and limits on the SUSY parameter space have been set. Measurements of the properties of the observed Higgs boson at ∝126 GeV as well as of the W boson mass (M W ) can provide valuable indirect constraints, supplementing the ones from direct searches. This thesis is divided into three major parts: In the first part we present the currently most precise prediction for M W in the Minimal Supersymmetric Standard Model (MSSM) with complex parameters and in the Next-to-Minimal Supersymmetric Standard Model (NMSSM). The evaluation includes the full one-loop result and all relevant available higher order corrections of Standard Model (SM) and SUSY type. We perform a detailed scan over the MSSM parameter space, taking into account the latest experimental results, including the observation of a Higgs signal. We find that the current measurements for M W and the top quark mass (m t ) slightly favour a non-zero SUSY contribution. The impact of different SUSY sectors on the prediction of M W as well as the size of the higher-order SUSY corrections are analysed both in the MSSM and the NMSSM. We investigate the genuine NMSSM contribution from the extended Higgs and neutralino sectors and highlight differences between the M W predictions in the two SUSY models. In the second part of the thesis we discuss possible interpretations of the observed Higgs signal in SUSY models. The properties of the observed Higgs boson are compatible with the SM so far, but many other interpretations are also possible. Performing scans over the relevant parts of the MSSM and the NMSSM parameter spaces and applying relevant constraints from Higgs searches, flavour physics and electroweak measurements, we find that a Higgs boson at ∝126 GeV, which decays into two photons, can in

Higgs Tasting Workshop 2016: Higgs and flavor in the LHC Run 2 era

CERN Document Server

2016-01-01

The discovery of a Higgs particle by the LHC experiments has launched the exploration of electroweak symmetry breaking and potentially opened a new window into beyond Standard Model physics. Measurements of Higgs boson properties during Run 1 of the LHC are broadly consistent with the Standard Model predictions, although they leave significant room for New Physics contributions. At the same time, a number of exciting anomalies in low-energy precision flavor observables have cumulated over the years, whose potential implications are yet to be fully gauged. One of the most pressing questions in high energy physics is the origin of flavor and it is undeniably linked in an intimate way to the physics of the Higgs boson. The Standard Model comes with definite predictions for the structure of the couplings between the Higgs boson and the fermions. Probing this structure or observing any deviation will have long-reaching implications on our understanding on how Nature works at its most fundamental level, including c...

A tale of twin Higgs: natural twin two Higgs doublet models

Energy Technology Data Exchange (ETDEWEB)

Yu, Jiang-Hao [Amherst Center for Fundamental Interactions, Department of Physics,University of Massachusetts Amherst,710 North Pleasant St., Amherst, MA 01002 (United States)

2016-12-28

In original twin Higgs model, vacuum misalignment between electroweak and new physics scales is realized by adding explicit ℤ{sub 2} breaking term. Introducing additional twin Higgs could accommodate spontaneous ℤ{sub 2} breaking, which explains origin of this misalignment. We introduce a class of twin two Higgs doublet models with most general scalar potential, and discuss general conditions which trigger electroweak and ℤ{sub 2} symmetry breaking. Various scenarios on realising the vacuum misalignment are systematically discussed in a natural composite two Higgs double model framework: explicit ℤ{sub 2} breaking, radiative ℤ{sub 2} breaking, tadpole-induced ℤ{sub 2} breaking, and quartic-induced ℤ{sub 2} breaking. We investigate the Higgs mass spectra and Higgs phenomenology in these scenarios.

Four generations and Higgs physics

Energy Technology Data Exchange (ETDEWEB)

Kribs, Graham D. [Department of Physics and Institute of Theoretical Science, University of Oregon, Eugene (United States); Plehn, Tilman [SUPA, School of Physics, University of Edinburgh (United Kingdom); Spannowsky, Michael [Institut fuer Theoretische Physik, Universitaet Karlsruhe (Germany); Tait, Tim M.P. [HEP Division, Argonne National Laboratory (United States)

2008-07-01

A fourth generation has been considered and forgotten or discarded several times, wrongly leaving the impression that it is either ruled out or disfavored by experimental data. We revisit a fourth generation of chiral matter in the light of present electroweak precision data and deduce effects on Higgs phenomenology. We find a chiral fourth generation to be a viable model which can yield interesting signatures at the LHC, e.g. production rates are enhanced, weak-boson-fusion channels are suppressed, angular distributions are modified and Higgs pairs can be observed.

New Physics Opportunities in the Boosted Di-Higgs-Boson Plus Missing Transverse Energy Signature.

Science.gov (United States)

Kang, Zhaofeng; Ko, P; Li, Jinmian

2016-04-01

The Higgs field in the standard model may couple to new physics sectors related to dark matter and/or massive neutrinos. In this Letter we propose a novel signature, the boosted di-Higgs-boson plus E_{T} (which is either a dark matter or neutrino), to probe those new physics sectors. In a large class of models, in particular, the supersymmetric standard models and low scale seesaw mechanisms, this signature can play a key role. The signature has a clear background, and at the sqrt[s]=14  TeV high luminosity LHC, we can probe it with a production rate as low as ∼0.1  fb. We apply it to benchmark models, supersymmetry in the bino-Higgsino limit, the canonical seesaw model, and the little Higgs model, finding that the masses of the Higgsino, right-handed neutrino, and heavy vector boson can be probed up to ∼500, 650, and 900 GeV, respectively.

Higgs physics: Theory

Indian Academy of Sciences (India)

2012-10-06

Oct 6, 2012 ... confidence level (CL) established at LEP2 [4]. ... particle is not self-consistent at high energies as it leads to ... matter and thus impact their density in the Universe today. ... s = 7 TeV LHC, lead to a K-factor KNLO ∼ 1.8 in the low Higgs mass ...... See Michael Spira, http://people.web.psi.ch/spira/proglist.html.

A review of Higgs mass calculations in supersymmetric models

DEFF Research Database (Denmark)

Draper, P.; Rzehak, H.

2016-01-01

The discovery of the Higgs boson is both a milestone achievement for the Standard Model and an exciting probe of new physics beyond the SM. One of the most important properties of the Higgs is its mass, a number that has proven to be highly constraining for models of new physics, particularly those...... related to the electroweak hierarchy problem. Perhaps the most extensively studied examples are supersymmetric models, which, while capable of producing a 125 GeV Higgs boson with SM-like properties, do so in non-generic parts of their parameter spaces. We review the computation of the Higgs mass...

The Standard Model and Higgs physics

Science.gov (United States)

Torassa, Ezio

2018-05-01

The Standard Model is a consistent and computable theory that successfully describes the elementary particle interactions. The strong, electromagnetic and weak interactions have been included in the theory exploiting the relation between group symmetries and group generators, in order to smartly introduce the force carriers. The group properties lead to constraints between boson masses and couplings. All the measurements performed at the LEP, Tevatron, LHC and other accelerators proved the consistency of the Standard Model. A key element of the theory is the Higgs field, which together with the spontaneous symmetry breaking, gives mass to the vector bosons and to the fermions. Unlike the case of vector bosons, the theory does not provide prediction for the Higgs boson mass. The LEP experiments, while providing very precise measurements of the Standard Model theory, searched for the evidence of the Higgs boson until the year 2000. The discovery of the top quark in 1994 by the Tevatron experiments and of the Higgs boson in 2012 by the LHC experiments were considered as the completion of the fundamental particles list of the Standard Model theory. Nevertheless the neutrino oscillations, the dark matter and the baryon asymmetry in the Universe evidence that we need a new extended model. In the Standard Model there are also some unattractive theoretical aspects like the divergent loop corrections to the Higgs boson mass and the very small Yukawa couplings needed to describe the neutrino masses. For all these reasons, the hunt of discrepancies between Standard Model and data is still going on with the aim to finally describe the new extended theory.

Handbook of LHC Higgs Cross Sections: 3. Higgs Properties

Energy Technology Data Exchange (ETDEWEB)

Heinemeyer, S; et al.

2013-01-01

This Report summarizes the results of the activities in 2012 and the first half of 2013 of the LHC Higgs Cross Section Working Group. The main goal of the working group was to present the state of the art of Higgs Physics at the LHC, integrating all new results that have appeared in the last few years. This report follows the first working group report Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002) and the second working group report Handbook of LHC Higgs Cross Sections: 2. Differential Distributions (CERN-2012-002). After the discovery of a Higgs boson at the LHC in mid-2012 this report focuses on refined prediction of Standard Model (SM) Higgs phenomenology around the experimentally observed value of 125-126 GeV, refined predictions for heavy SM-like Higgs bosons as well as predictions in the Minimal Supersymmetric Standard Model and first steps to go beyond these models. The other main focus is on the extraction of the characteristics and properties of the newly discovered particle such as couplings to SM particles, spin and CP-quantum numbers etc.

Your Higgs number - how fundamental physics is connected to technology and societal revolutions

Science.gov (United States)

Lidström, Suzy; Allen, Roland E.

2015-03-01

Fundamental physics, as exemplified by the recently discovered Higgs boson, often appears to be completely disconnected from practical applications and ordinary human life. But this is not really the case, because science, technology, and human affairs are profoundly integrated in ways that are not immediately obvious. We illustrate this by defining a ``Higgs number'' through overlapping activities. Following three different paths, which end respectively in applications of the World Wide Web, digital photography, and modern electronic devices, we find that most people have a Higgs number of no greater than 3. Specific examples chosen for illustration, with their assigned Higgs numbers, are: LHC experimentalists employing the Worldwide Computing Grid (0) - Timothy Berners-Lee (1) - Marissa Mayer, of Google and Yahoo, and Sheryl Sandberg, of Facebook (2) - users of all web-based enterprises (3). CMS and ATLAS experimentalists (0) - particle detector developers (1) - inventors of CCDs and active-pixel sensors (2) - users of digital cameras and camcorders (3). Philip Anderson (0) - John Bardeen (1) - Jack Kilby (2) - users of personal computers, mobile phones, and all other modern electronic devices (3).

Beyond-the-Standard Model Higgs Physics using the ATLAS Experiment

CERN Document Server

Madsen, Alexander; The ATLAS collaboration

2015-01-01

The discovery of a Higgs boson with a mass of about 125 GeV has prompted the question of whether or not this particle is part of a larger and more complex Higgs sector than that envisioned in the Standard Model. In this talk, the latest results from the ATLAS experiment on Beyond-the-Standard Model (BSM) Higgs searches are outlined. Searches for additional Higgs bosons are presented and interpreted in well-motivated BSM Higgs frameworks, such as two-Higgs-doublet Models and the Minimal and Next to Minimal Supersymmetric Standard Model.

Beyond-the-Standard Model Higgs Physics using the ATLAS Experiment

CERN Document Server

Vanadia, Marco; The ATLAS collaboration

2015-01-01

The discovery of a Higgs boson with a mass of about 125 GeV has prompted the question of whether or not this particle is part of a larger and more complex Higgs sector than that envisioned in the Standard Model. In this talk, the latest Run 1 results from the ATLAS Experiment on Beyond-the-Standard Model (BSM) Higgs searches are outlined. Searches for additional Higgs bosons are presented and interpreted in wellmotivated BSM Higgs frameworks, including the two-Higgs-doublet Models and the Minimal and Next to Minimal Supersymmetric Standard Model.

Beyond-the-Standard Model Higgs Physics using the ATLAS Experiment

CERN Document Server

Scutti, Federico; The ATLAS collaboration

2015-01-01

The discovery of a Higgs boson with a mass of about 125 GeV has prompted the question of whether or not this particle is part of a larger and more complex Higgs sector than that envisioned in the Standard Model. In this talk, the current results from the ATLAS experiment on Beyond-the-Standard Model (BSM) Higgs searches are summarized. Searches for additional Higgs bosons are presented and interpreted in well-motivated BSM Higgs frameworks, such as two-Higgs-doublet Models and the Minimal and Next to Minimal Supersymmetric Standard Model.

Beyond-the-Standard Model Higgs Physics using the ATLAS Experiment

CERN Document Server

Nagata, Kazuki; The ATLAS collaboration

2014-01-01

The discovery of a Higgs boson with a mass of about 125 GeV has prompted the question of whether or not this particle is part of a larger and more complex Higgs sector than that envisioned in the Standard Model. In this talk, the current results from the ATLAS experiment on Beyond-the-Standard Model (BSM) Higgs searches are outlined. Searches for additional Higgs bosons are presented and interpreted in well-motivated BSM Higgs frameworks, such as two-Higgs-doublet Models and the Minimal and Next to Minimal Supersymmetric Standard Model.

Beyond-the-Standard Model Higgs physics using the ATLAS experiment

CERN Document Server

Ernis, G; The ATLAS collaboration

2014-01-01

The discovery of a Higgs boson with a mass of about 125 GeV has prompted the question of whether or not this particle is part of a larger and more complex Higgs sector than that envisioned in the Standard Model. In this talk, the current results from the ATLAS experiment on Beyond-the-Standard Model (BSM) Higgs searches are outlined. Searches for additional Higgs bosons are presented and interpreted in well-motivated BSM Higgs frameworks, such as two-Higgs-doublet Models and the Minimal and Next to Minimal Supersymmetric Standard Model.

Systematic study of Higgs masses in the MSSM

CERN Document Server

Ghosh, B

2000-01-01

The Higgs masses in the minimal supersymmetric standard model at extremely high energies relevant to LEP2 and LHC have been studied. The results of systematic studies on Higgs masses for the possible ranges of all the parameters in the case of 1-loop radiative correction to the Higgs boson masses have been given. On the basis of detailed analyses we come to interesting constraints on the Higgs masses in the minimal supersymmetric standard model. (11 refs).

The HiggsTools handbook: a beginners guide to decoding the Higgs sector

Science.gov (United States)

Boggia, M.; Cruz-Martinez, J. M.; Frellesvig, H.; Glover, N.; Gomez-Ambrosio, R.; Gonella, G.; Haddad, Y.; Ilnicka, A.; Jones, S.; Kassabov, Z.; Krauss, F.; Megy, T.; Melini, D.; Napoletano, D.; Passarino, G.; Patel, S.; Rodriguez-Vazquez, M.; Wolf, T.

2018-06-01

This report summarises some of the activities of the HiggsTools initial training network working group in the period 2015–2017. The main goal of this working group was to produce a document discussing various aspects of state-of-the-art Higgs physics at the large hadron collider (LHC) in a pedagogic manner. The first part of the report is devoted to a description of phenomenological searches for new physics (NP) at the LHC. All of the available studies of the couplings of the new resonance discovered in 2012 by the ATLAS and CMS experiments (Aad et al (ATLAS Collaboration) 2012 Phys. Lett. B 716 1–29 Chatrchyan et al (CMS Collaboration) 2012 Phys. Lett. B 716 30–61) conclude that it is compatible with the Higgs boson of the standard model (SM) within present precision. So far the LHC experiments have given no direct evidence for any physical phenomena that cannot be described by the SM. As the experimental measurements become more and more precise, there is a pressing need for a consistent framework in which deviations from the SM predictions can be computed precisely. Such a framework should be applicable to measurements in all sectors of particle physics, not only LHC Higgs measurements but also electroweak precision data, etc. We critically review the use of the κ-framework, fiducial and simplified template cross sections, effective field theories, pseudoobservables and phenomenological Lagrangians. Some of the concepts presented here are well known and were used already at the time of the large electron–positron collider (LEP) experiment. However, after years of theoretical and experimental development, these techniques have been refined, and we describe new tools that have been introduced in order to improve the comparison between theory and experimental data. In the second part of the report, we propose {φ }η * as a new and complementary observable for studying Higgs boson production at large transverse momentum in the case where the Higgs boson

Interplay of Higgs phenomenology and new physics in supersymmetric theories

Energy Technology Data Exchange (ETDEWEB)

Patel, Shruti

2017-10-15

crosssection predictions into an extension of the numerical code SusHi, named SusHiMi. In our numerical analysis, we employ SusHiMi to study the effects of the phase of the soft SUSY-breaking trilinear coupling of the Higgs with the top squark, and of the phase of the gluino mass parameter on the neutral Higgs cross sections, masses, and mixings. We demonstrate that squark effects can be strongly dependent on the phases of the complex parameters, and emphasise the relevance of the resummation of squark effects in the bottom-Yukawa coupling. Furthermore, we show that in a scenario where the two heavy Higgs bosons, h{sub 2} and h{sub 3}, are strongly admixed and nearly mass-degenerate, experimentally resolving the two Higgs bosons as separate signals may not be possible. Only the sum of their cross sections including interference terms can be measured experimentally. Finally, we incorporate our cross section predictions into a formalism to account for the CP-violating interference between the Higgs bosons. In the prediction of the process b anti b→hh{sub 3}→τ{sup +}τ{sup -}, we show that strongly destructive interference arises in the benchmark scenario defined in this thesis. Consequently, considerable parameter regions escape the exclusion bounds, which would be ruled out in LHC searches which neglect these interference contributions.

Interplay of Higgs phenomenology and new physics in supersymmetric theories

International Nuclear Information System (INIS)

Patel, Shruti

2017-10-01

crosssection predictions into an extension of the numerical code SusHi, named SusHiMi. In our numerical analysis, we employ SusHiMi to study the effects of the phase of the soft SUSY-breaking trilinear coupling of the Higgs with the top squark, and of the phase of the gluino mass parameter on the neutral Higgs cross sections, masses, and mixings. We demonstrate that squark effects can be strongly dependent on the phases of the complex parameters, and emphasise the relevance of the resummation of squark effects in the bottom-Yukawa coupling. Furthermore, we show that in a scenario where the two heavy Higgs bosons, h 2 and h 3 , are strongly admixed and nearly mass-degenerate, experimentally resolving the two Higgs bosons as separate signals may not be possible. Only the sum of their cross sections including interference terms can be measured experimentally. Finally, we incorporate our cross section predictions into a formalism to account for the CP-violating interference between the Higgs bosons. In the prediction of the process b anti b→hh 3 →τ + τ - , we show that strongly destructive interference arises in the benchmark scenario defined in this thesis. Consequently, considerable parameter regions escape the exclusion bounds, which would be ruled out in LHC searches which neglect these interference contributions.

Probing Higgs self-coupling of a classically scale invariant model in e+e- → Zhh: Evaluation at physical point

Science.gov (United States)

Fujitani, Y.; Sumino, Y.

2018-04-01

A classically scale invariant extension of the standard model predicts large anomalous Higgs self-interactions. We compute missing contributions in previous studies for probing the Higgs triple coupling of a minimal model using the process e+e- → Zhh. Employing a proper order counting, we compute the total and differential cross sections at the leading order, which incorporate the one-loop corrections between zero external momenta and their physical values. Discovery/exclusion potential of a future e+e- collider for this model is estimated. We also find a unique feature in the momentum dependence of the Higgs triple vertex for this class of models.

Higgs boson studies at the Tevatron

Czech Academy of Sciences Publication Activity Database

Aaltonen, L.; Abbott, B.; Abazov, V. M.; Kupčo, Alexander; Lokajíček, Miloš; Lysák, Roman

2013-01-01

Roč. 88, č. 5 (2013), "052014-1"-"052014-29" ISSN 1550-7998 R&D Projects: GA MŠk(CZ) LG12006 Institutional support: RVO:68378271 Keywords : Higgs particle * mass * vector boson * gluon * fusion * Batavia TEVATRON Coll * CDF * DZERO * anti-p p * interaction Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 4.864, year: 2013

Handbook of LHC Higgs Cross Sections: 3. Higgs Properties Report of the LHC Higgs Cross Section Working Group

CERN Document Server

Heinemeyer, S; Passarino, G; Tanaka, R; Andersen, J R; Artoisenet, P; Bagnaschi, E A; Banfi, A; Becher, T; Bernlochner, F U; Bolognesi, S; Bolzoni, P; Boughezal, R; Buarque, D; Campbell, J; Caola, F; Carena, M; Cascioli, F; Chanon, N; Cheng, T; Choi, S Y; David, A; de Aquino, P; Degrassi, G; Del Re, D; Denner, A; van Deurzen, H; Diglio, S; Di Micco, B; Di Nardo, R; Dittmaier, S; Dührssen, M; Ellis, R K; Ferrera, G; Fidanza, N; Flechl, M; de Florian, D; Forte, S; Frederix, R; Frixione, S; Gangal, S; Gao, Y; Garzelli, M V; Gillberg, D; Govoni, P; Grazzini, M; Greiner, N; Griffiths, J; Gritsan, A V; Grojean, C; Hall, D C; Hays, C; Harlander, R; Hernandez-Pinto, R; Höche, S; Huston, J; Jubb, T; Kadastik, M; Kallweit, S; Kardos, A; Kashif, L; Kauer, N; Kim, H; Klees, R; Krämer, M; Krauss, F; Laureys, A; Laurila, S; Lehti, S; Li, Q; Liebler, S; Liu, X; Logan, E; Luisoni, G; Malberti, M; Maltoni, F; Mawatari, K; Maierhoefer, F; Mantler, H; Martin, S; Mastrolia, P; Mattelaer, O; Mazzitelli, J; Mellado, B; Melnikov, K; Meridiani, P; Miller, D J; Mirabella, E; Moch, S O; Monni, P; Moretti, N; Mück, A; Mühlleitner, M; Musella, P; Nason, P; Neu, C; Neubert, M; Oleari, C; Olsen, J; Ossola, G; Peraro, T; Peters, K; Petriello, F; Piacquadio, G; Potter, C T; Pozzorini, S; Prokofiev, K; Puljak, I; Rauch, M; Rebuzzi, D; Reina, L; Rietkerk, R; Rizzi, A; Rotstein-Habarnau, Y; Salam, G P; Sborlini, G; Schissler, F; Schönherr, M; Schulze, M; Schumacher, M; Siegert, F; Slavich, P; Smillie, J M; Stål, O; von Soden-Fraunhofen, J F; Spira, M; Stewart, I W; Tackmann, F J; Taylor, P T E; Tommasini, D; Thompson, J; Thorne, R S; Torrielli, P; Tramontano, F; Tran, N V; Trócsányi, Z; Ubiali, M; Vazquez Acosta, M; Vickey, T; Vicini, A; Waalewijn, W J; Wackeroth, D; Wagner, C; Walsh, J R; Wang, J; Weiglein, G; Whitbeck, A; Williams, C; Yu, J; Zanderighi, G; Zanetti, M; Zaro, M; Zerwas, P M; Zhang, C; Zirke, T J E; Zuberi, S

2013-01-01

This Report summarizes the results of the activities in 2012 and the first half of 2013 of the LHC Higgs Cross Section Working Group. The main goal of the working group was to present the state of the art of Higgs Physics at the LHC, integrating all new results that have appeared in the last few years. This report follows the first working group report Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002) and the second working group report Handbook of LHC Higgs Cross Sections: 2. Differential Distributions (CERN-2012-002). After the discovery of a Higgs boson at the LHC in mid-2012 this report focuses on refined prediction of Standard Model (SM) Higgs phenomenology around the experimentally observed value of 125-126 GeV, refined predictions for heavy SM-like Higgs bosons as well as predictions in the Minimal Supersymmetric Standard Model and first steps to go beyond these models. The other main focus is on the extraction of the characteristics and properties of the newly discovered p...

A Brief Survey of Higgs Bundles

OpenAIRE

Zúñiga-Rojas, Ronald Alberto

2018-01-01

Considering a compact Riemann surface of genus greater than two, a Higgs~bundle is a pair composed of a holomorphic bundle over the Riemann surface, joint with an auxiliar vector field, so-called Higgs field. This theory started around thirty years ago, with Hitchin's work, when he reduced the self-duality equations from dimension four to dimension two, and so, studied those equations over Riemann surfaces. Hitchin baptized those fields as "Higgs fields" beacuse in the context of physics and ...

Beyond-the-Standard Model Higgs Physics using the ATLAS Experiment

CERN Document Server

Vanadia, Marco; The ATLAS collaboration

2015-01-01

The discovery of a Higgs boson with a mass of about 125 GeV/$\\rm{c^2}$ has prompted the question of whether or not this particle is part of a larger and more complex Higgs sector than that envisioned in the Standard Model. In this report, the latest Run 1 results from the ATLAS Experiment on Beyond-the-Standard Model (BSM) Higgs searches are outlined. Searches for additional Higgs bosons are presented and interpreted in well motivated BSM Higgs frameworks, including the two-Higgs-doublet Models and the Minimal and Next to Minimal Supersymmetric Standard Model.

Light Higgs bosons in phenomenological NMSSM

International Nuclear Information System (INIS)

Mahmoudi, F.; Rathsman, J.; Zeune, L.; Goettingen Univ.

2010-12-01

We consider scenarios in the next-to-minimal supersymmetric model (NMSSM) where the CP-odd and charged Higgs bosons are very light. As we demonstrate, these can be obtained as simple deformations of existing phenomenological MSSM benchmarks scenarios with parameters defined at the weak scale. This offers a direct and meaningful comparison to the MSSM case. Applying a wide set of up-to-date constraints from both high-energy collider and flavour physics, the Higgs boson masses and couplings are studied in viable parts of parameter space. The LHC phenomenology of the light Higgs scenario for neutral and charged Higgs boson searches is discussed. (orig.)

Light Higgs bosons in phenomenological NMSSM

Energy Technology Data Exchange (ETDEWEB)

Mahmoudi, F. [CERN, Geneva (Switzerland); Clermont Univ., CNRS/IN2P3, LPC, Clermont-Ferrand (France); Rathsman, J. [Uppsala Univ. (Sweden). High-Energy Physics; Lund Univ. (Sweden). Theoretical High Energy Physics; Staal, O. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Zeune, L. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Goettingen Univ. (Germany). II. Physikalisches Inst.

2010-12-15

We consider scenarios in the next-to-minimal supersymmetric model (NMSSM) where the CP-odd and charged Higgs bosons are very light. As we demonstrate, these can be obtained as simple deformations of existing phenomenological MSSM benchmarks scenarios with parameters defined at the weak scale. This offers a direct and meaningful comparison to the MSSM case. Applying a wide set of up-to-date constraints from both high-energy collider and flavour physics, the Higgs boson masses and couplings are studied in viable parts of parameter space. The LHC phenomenology of the light Higgs scenario for neutral and charged Higgs boson searches is discussed. (orig.)

High performance computing system in the framework of the Higgs boson studies

CERN Document Server

Belyaev, Nikita; The ATLAS collaboration; Velikhov, Vasily; Konoplich, Rostislav

2017-01-01

The Higgs boson physics is one of the most important and promising fields of study in the modern high energy physics. It is important to notice, that GRID computing resources become strictly limited due to increasing amount of statistics, required for physics analyses and unprecedented LHC performance. One of the possibilities to address the shortfall of computing resources is the usage of computer institutes' clusters, commercial computing resources and supercomputers. To perform precision measurements of the Higgs boson properties in these realities, it is also highly required to have effective instruments to simulate kinematic distributions of signal events. In this talk we give a brief description of the modern distribution reconstruction method called Morphing and perform few efficiency tests to demonstrate its potential. These studies have been performed on the WLCG and Kurchatov Institute’s Data Processing Center, including Tier-1 GRID site and supercomputer as well. We also analyze the CPU efficienc...

The Higgs boson resonance width from a chiral Higgs-Yukawa model on the lattice

International Nuclear Information System (INIS)

Gerhold, Philipp; Kallarackal, Jim; Humboldt-Universitaet, Berlin; Jansen, Karl

2011-11-01

The Higgs boson is a central part of the electroweak theory and is crucial to generate masses for quarks, leptons and the weak gauge bosons. We use a 4-dimensional Euclidean lattice formulation of the Higgs-Yukawa sector of the electroweak model to compute physical quantities in the path integral approach which is evaluated by means of Monte Carlo simulations thus allowing for fully non perturbative calculations. The chiral symmetry of the model is incorporated by using the Neuberger overlap Dirac operator. The here considered Higgs-Yukawa model does not involve the weak gauge bosons and furthermore, only a degenerate doublet of top- and bottom quarks are incorporated. The goal of this work is to study the resonance properties of the Higgs boson and its sensitivity to the strength of the quartic self coupling. (orig.)

Higgs into the heart of imagination

CERN Document Server

Van den Bergh, Hannie

2010-01-01

Higgs is the documentary about the quest for the Higgs particle, also known as "The God Particle". It is considered the missing link in particle physics. Higgs is a film about the curiosity, the passion, and the imaginative power of silence.

Character Profile of the Higgs boson

CERN Document Server

AUTHOR|(INSPIRE)INSPIRE-00386479; Bentvelsen, Stan; Ferrari, Pamela

Elementary particle physics describes and measures the properties of the smallest, most fundamental particles that make up the universe. The Standard Model of elementary particle physics provides a fundamental description of particles, their dynamics and interactions. The particles embedded into the theory are, a priori, massless, while observed particles have mass. In order to explain the origin of the elementary particle masses, the Brout-Englert-Higgs mechanism is introduced. The mechanism introduces the existence of one real scalar field, with the Higgs boson as excitation, however it does not predict its mass. To verify that the Higgs mechanism is the origin of elementary particle masses is one of the main goals of the Large Hadron Collider (LHC) programs at CERN. Higgs physics at the ATLAS detector has reached an exciting new phase of precision measurements, but the analyses are still mostly set up for conducting searches. The research shown in this thesis has provided measurements in the Higgs sector, ...

Simulation Study of Invisible Decays of the Higgs Boson with the Circular Electron Positron Collider

Science.gov (United States)

Jyotishmati, Susmita

A Higgs-like boson has been discovered by the experiments ATLAS and CMS at the LHC. We need to verify that it is the Standard Model (SM) Higgs and understand its nature. A Circular Electron Positron Collider (CEPC), has been proposed as a Higgs factory for detailed study of the Higgs boson. In this dissertation we study the feasibility of measuring the H → Invisible decays at the CEPC. Dark Matter (DM) interacts with matter by gravity, thus appears to be invisible in the CEPC experiment. If Higgs boson couples to DM it could be an important "portal" to New Physics. A Monte Carlo analysis of H → Invisible optimized to achieve high signal significance, and low backgrounds in the e +e- → ZH, Z → mu +mu- channel based on an integrated luminosity of 5 ab-1 expected for ten years run of the CEPC, is performed. Precision on the Higgs to invisible branching ratio at the input values of 0.1%(SM) and Beyond Standard Model (BSM) cases 0%, 1%, 5% and 10% is determined. Two approaches have been employed. They are the cut-based analysis and the multivariate analysis. Based on this dissertation study a baseline analysis approach is recommended for future CEPC design and studies.

John Ellis discusses the Higgs, the lack of the Higgs, and extra dimensions

CERN Multimedia

Katarina Anthony

2011-01-01

On 13 September, CERN will be hosting a colloquium to mark John Ellis' 65th birthday. The colloquium comes as John ends his long career as a distinguished CERN staff member and makes a transition to Clerk Maxwell Professor of Theoretical Physics at King’s College London. The Bulletin took the opportunity to ask John to share his expectations from the LHC during this long-awaited data-taking phase...   John Ellis  in his office (July 2011). So, let’s start from the Higgs boson: does it exist and where is it? The million-dollar question… Sometime in the next few months, I think we will finally get clarity on the Higgs boson. While it has been with us as a hypothesis since 1964, I think we are finally closing in on it now. However, in every possible discovery scenario, clarity on the Higgs will lead to new physics. Let me explain... Experiments have left only three possible mass ranges where the Higgs – or a Higgs-like particl...

HiggsToFourLeptonsEV in the ATLAS EventView Analysis Framework

CERN Document Server

Lagouri, T; Del Peso, J

2008-01-01

ATLAS is one of the four experiments at the Large Hadron Collider (LHC) at CERN. This experiment has been designed to study a large range of physics topics, including searches for previously unobserved phenomena such as the Higgs Boson and super-symmetry. The physics analysis package HiggsToFourLeptonsEV for the Standard Model (SM) Higgs to four leptons channel with ATLAS is presented. The physics goal is to investigate with the ATLAS detector, the SM Higgs boson discovery potential through its observation in the four-lepton (electron and muon) final state. HiggsToFourLeptonsEV is based on the official ATLAS software ATHENA and the EventView (EV) analysis framework. EventView is a highly flexible and modular analysis framework in ATHENA and it is one of several analysis schemes for ATLAS physics user analysis. At the core of the EventView is the representative "view" of an event, which defines the contents of event data suitable for event-level physics analysis. The HiggsToFourLeptonsEV package, presented in ...

Phenomenology of the Higgs effective Lagrangian via F eynR ules

Science.gov (United States)

Alloul, Adam; Fuks, Benjamin; Sanz, Verónica

2014-04-01

The Higgs discovery and the lack of any other hint for new physics favor a description of non-standard Higgs physics in terms of an effective field theory. We present an implementation of a general Higgs effective Lagrangian containing operators up to dimension six in the framework of F eynR ules and provide details on the translation between the mass and interaction bases, in particular for three- and four-point interaction vertices involving Higgs and gauge bosons. We illustrate the strengths of this implementation by using the UFO interface of F eynR ules capable to generate model files that can be understood by the M adG raph 5 event generator and that have the specificity to contain all interaction vertices, without any restriction on the number of external legs or on the complexity of the Lorentz structures. We then investigate several new physics effects in total rates and differential distributions for different Higgs production modes, including gluon fusion, associated production with a gauge boson and di-Higgs production. We finally study contact interactions of gauge and Higgs bosons to fermions.

A Historical Profile of the Higgs Boson

Energy Technology Data Exchange (ETDEWEB)

Ellis, John; Gaillard, Mary K.; Nanopoulos, Dimitri V.

2012-01-31

The Higgs boson was postulated in 1964, and phenomenological studies of its possible production and decays started in the early 1970s, followed by studies of its possible productionin e{sup +} e{sup -}, {anti p}p and pp collisions, in particular. Until recently, the most sensitive searches for the Higgs boson were at LEP between 1989 and 2000, which have been complemented bysearches at the Fermilab Tevatron. The LHC has recently entered the hunt, excluding a Higgs boson over a large range of masses and revealing a tantalizing hint in the range 119 to125 GeV, and there are good prospects that the existence or otherwise of the Higgs boson will soon be established. One of the most attractive possibilities is that the Higgs bosonis accompanied by supersymmetry, though composite options have yet to be excluded. This article reviews some of the key historical developments in Higgs physics over the past half-century.

Off-Shell Higgs Probe of Naturalness

Science.gov (United States)

Gonçalves, Dorival; Han, Tao; Mukhopadhyay, Satyanarayan

2018-03-01

Examining the Higgs sector at high energy scales through off-shell Higgs production can potentially shed light on the naturalness problem of the Higgs boson mass. We propose such a study at the LHC by utilizing a representative model with a new scalar field (S ) coupled to the standard model Higgs doublet (H ) in a form |S |2|H |2. In the process p p →h*→Z Z , the dominant momentum-dependent part of the one-loop scalar singlet corrections, especially above the new threshold at 2 mS, leads to a measurable deviation in the differential distribution of the Z -pair invariant mass, in accordance with the quadratic divergence cancellation to the Higgs mass. We find that it is conceivable to probe such new physics at the 5 σ level at the high-luminosity LHC, improving further with the upgraded 27 TeV LHC, without requiring the precise measurement of the Higgs boson total width. The discovery of such a Higgs portal could also have important implications for thermal dark matter as well as for electroweak baryogenesis.

Beyond the standard Higgs after the 125 GeV Higgs discovery.

Science.gov (United States)

Grojean, C

2015-01-13

An elementary weakly coupled and solitary Higgs boson allows one to extend the validity of the Standard Model up to very high energy, maybe as high as the Planck scale. Nonetheless, this scenario fails to fill the universe with dark matter and does not explain the matter-antimatter asymmetry. However, amending the Standard Model tends to destabilize the weak scale by large quantum corrections to the Higgs potential. New degrees of freedom, new forces, new organizing principles are required to provide a consistent and natural description of physics beyond the standard Higgs.

Where is the Higgs-boson

International Nuclear Information System (INIS)

Cahn, R.; Froidevaux, D.; Grivaz, J.F.; King, S.F.; Mansoulie, B.; Taxil, P.

1990-01-01

The 22th session of Summer School on Particle Physics was held in Strasbourg from 3 to 7 September 1990. The subject 'Where is the Higgs' and all aspects of this question have been studied in lessons and discussions: actual researches of Higgs at LEP in the Standard Model or not, future researches in hadron collisions of very high energy and hard technical problems that the experiments set near to the future hadron colliders

From condensed matter to Higgs physics. Solving functional renormalization group equations globally in field space

Energy Technology Data Exchange (ETDEWEB)

Borchardt, Julia

2017-02-07

By means of the functional renormalization group (FRG), systems can be described in a nonperturbative way. The derived flow equations are solved via pseudo-spectral methods. As they allow to resolve the full field dependence of the effective potential and provide highly accurate results, these numerical methods are very powerful but have hardly been used in the FRG context. We show their benefits using several examples. Moreover, we apply the pseudo-spectral methods to explore the phase diagram of a bosonic model with two coupled order parameters and to clarify the nature of a possible metastability of the Higgs-Yukawa potential.In the phase diagram of systems with two competing order parameters, fixed points govern multicritical behavior. Such systems are often discussed in the context of condensed matter. Considering the phase diagram of the bosonic model between two and three dimensions, we discover additional fixed points besides the well-known ones from studies in three dimensions. Interestingly, our findings suggest that in certain regions of the phase diagram, two universality classes coexist. To our knowledge, this is the first bosonic model where coexisting (multi-)criticalities are found. Also, the absence of nontrivial fixed points can have a physical meaning, such as in the electroweak sector of the standard model which suffers from the triviality problem. The electroweak transition giving rise to the Higgs mechanism is dominated by the Gaussian fixed point. Due to the low Higgs mass, perturbative calculations suggest a metastable potential. However, the existence of the lower Higgs-mass bound eventually is interrelated with the maximal ultraviolet extension of the standard model. A relaxation of the lower bound would mean that the standard model may be still valid to even higher scales. Within a simple Higgs-Yukawa model, we discuss the origin of metastabilities and mechanisms, which relax the Higgs-mass bound, including higher field operators.

Higgs Boson Measurements in CMS with Run II Data

CERN Document Server

Kumar, Ashok

2017-01-01

Latest results from the CMS experiment on studies of Higgs boson production are presented. Studies involving the 125 GeV Higgs boson using various Standard Model production and decay modes have been performed using proton proton collisions from data accumulated during the LHC Run II with center-of-mass energy of 13 TeV. Similar datasets have also been used to place constraints on physics beyond the Standard Model involving extended Higgs boson sectors.

Unitarity and predictiveness in new Higgs inflation

Science.gov (United States)

Fumagalli, Jacopo; Mooij, Sander; Postma, Marieke

2018-03-01

In new Higgs inflation the Higgs kinetic terms are non-minimally coupled to the Einstein tensor, allowing the Higgs field to play the role of the inflaton. The new interaction is non-renormalizable, and the model only describes physics below some cutoff scale. Even if the unknown UV physics does not affect the tree level inflaton potential significantly, it may still enter at loop level and modify the running of the Standard Model (SM) parameters. This is analogous to what happens in the original model for Higgs inflation. A key difference, though, is that in new Higgs inflation the inflationary predictions are sensitive to this running. Thus the boundary conditions at the EW scale as well as the unknown UV completion may leave a signature on the inflationary parameters. However, this dependence can be evaded if the kinetic terms of the SM fermions and gauge fields are non-minimally coupled to gravity as well. Our approach to determine the model's UV dependence and the connection between low and high scale physics can be used in any particle physics model of inflation.

SM-like Higgs decay into two muons at 1.4 TeV CLIC

CERN Document Server

Milutinovic-Dumbelovic, G

2014-01-01

The potential for measuring the Standard Model (SM) Higgs boson decay into two muons at a 1.4 TeV CLIC e+e− collider is addressed in this paper, that was presented at ICHEP2014. The study is performed in the full Geant4 detector simulations of CLIC_ILD, taking into consideration all the relevant physics and the beam-induced background processes, as well as the instrumentation of the very forward region to tag forward electrons. In this analysis we show that the branching ratio BR(H-->mu+mu-) times the Higgs production cross-section can be measured with 38% statistical accuracy at √s =1.4 TeV using an integrated luminosity of 1.5 ab-1. This study is part of an ongoing comprehensive Higgs physics benchmark study covering various Higgs production processes and decay modes, currently being carried out to estimate the full Higgs physics potential of CLIC.

Usefulness of effective field theory for boosted Higgs production

Energy Technology Data Exchange (ETDEWEB)

Dawson, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Lewis, I. M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Zeng, Mao [Stony Brook Univ., Stony Brook, NY (United States)

2015-04-07

The Higgs + jet channel at the LHC is sensitive to the effects of new physics both in the total rate and in the transverse momentum distribution at high _pT. We examine the production process using an effective field theory (EFT) language and discussing the possibility of determining the nature of the underlying high-scale physics from boosted Higgs production. The effects of heavy color triplet scalars and top partner fermions with TeV scale masses are considered as examples and Higgs-gluon couplings of dimension-5 and dimension-7 are included in the EFT. As a byproduct of our study, we examine the region of validity of the EFT. Dimension-7 contributions in realistic new physics models give effects in the high _pT tail of the Higgs signal which are so tiny that they are likely to be unobservable.

Experimental study of the Higgs-b/c couplings in photon-proton collisions

International Nuclear Information System (INIS)

Franck, Joachim

2011-06-01

After the commissioning of the Large Hadron Collider, new insights into the physics of elementary particles are expected, in particular, particle physicists hope for the detection of the Higgs boson. Measuring the Higgs couplings to the charm and beauty quarks will be of great importance to verify or to falsify existing theories in particle physics. In the present diploma thesis, it has been studied whether the couplings mentioned above would be measurable at a Large Hadron-Photon Collider in associated production. On one hand, the design parameters of such a machine were investigated, on the other hand, several simulation programs were used to predict essential properties of the desired processes, like cross sections and kinematics. The result of the present work is that the single events are detectable and, for the beauty process, the background is low enough for the events to stand out. However, using the present technology, the required luminosity can not be achieved. Detailed introductions into the physical and technological concepts hat are fundamental for this study as well as into the used software round off the thesis' contents. (orig.)

Higgs-Palatini inflation and unitarity

International Nuclear Information System (INIS)

Bauer, Florian; Demir, Durmus A.

2011-01-01

In the Higgs inflation scenario the Higgs field is strongly coupled to the Ricci scalar in order to drive primordial inflation. However, in its original form in pure metric formulation of gravity, the ultraviolet (UV) cutoff of the Higgs interactions and the Hubble rate are of the same magnitude, and this makes the whole inflationary evolution dependent of the unknown UV completion of the Higgs sector. This problem, the unitarity violation, plagues the Higgs inflation scenario. In this Letter we show that, in the Palatini formulation of gravitation, Higgs inflation does not suffer from unitarity violation since the UV cutoff lies parametrically much higher than the Hubble rate so that unknown UV physics does not disrupt the inflationary dynamics. Higgs-Palatini inflation, as we call it, is, therefore, UV-safe, minimal and endowed with predictive power.

Tools for charged Higgs bosons

International Nuclear Information System (INIS)

Staal, Oscar

2010-12-01

We review the status of publicly available software tools applicable to charged Higgs physics. A selection of codes are highlighted in more detail, focusing on new developments that have taken place since the previous charged Higgs workshop in 2008. We conclude that phenomenologists now have the tools ready to face the LHC data. A new web page collecting charged Higgs resources is presented. (orig.)

Bound states via Higgs exchanging and heavy resonant di-Higgs

Directory of Open Access Journals (Sweden)

Zhaofeng Kang

2017-08-01

Full Text Available The existence of Higgs boson h predicted by the standard model (SM was established and hunting for clues to new physics (NP hidden in h has become the top priority in particle physics. In this paper we explore an intriguing phenomenon that prevails in NP associated with h, bound state (Bh, referring to the ground state only of relatively heavy particles ϕ out of NP via interchanging h. This is well-motivated due to the intrinsic properties of h: It has zero spin and light mass, capable of mediating Yukawa interactions; moreover, it may be strongly coupled to ϕ in several important contexts, from addressing the naturalness problem by compositeness/supersymmetry (SUSY/classical scale invariance to understanding neutrino mass origin radiatively and matter asymmetry by electroweak baryogensis. The new resonance Bh, being a neutral scalar boson, has important implications to the large hadron collider (LHC di-Higgs search because it yields a clear resonant di-Higgs signature at the high mass region (≳1 TeV. In other words, searching for Bh offers a new avenue to probe the hidden sector with a Higgs-portal. For illustration in this paper we concentrate on two examples, the stop sector in SUSY and an inert Higgs doublet from a radiative neutrino model. In particular, h-mediation opens a new and wide window to probe the conventional stoponium and the current date begins to have sensitivity to stoponium around TeV.

Bound states via Higgs exchanging and heavy resonant di-Higgs

Science.gov (United States)

Kang, Zhaofeng

2017-08-01

The existence of Higgs boson h predicted by the standard model (SM) was established and hunting for clues to new physics (NP) hidden in h has become the top priority in particle physics. In this paper we explore an intriguing phenomenon that prevails in NP associated with h, bound state (Bh, referring to the ground state only) of relatively heavy particles ϕ out of NP via interchanging h. This is well-motivated due to the intrinsic properties of h: It has zero spin and light mass, capable of mediating Yukawa interactions; moreover, it may be strongly coupled to ϕ in several important contexts, from addressing the naturalness problem by compositeness/supersymmetry (SUSY)/classical scale invariance to understanding neutrino mass origin radiatively and matter asymmetry by electroweak baryogensis. The new resonance Bh, being a neutral scalar boson, has important implications to the large hadron collider (LHC) di-Higgs search because it yields a clear resonant di-Higgs signature at the high mass region (≳ 1 TeV). In other words, searching for Bh offers a new avenue to probe the hidden sector with a Higgs-portal. For illustration in this paper we concentrate on two examples, the stop sector in SUSY and an inert Higgs doublet from a radiative neutrino model. In particular, h-mediation opens a new and wide window to probe the conventional stoponium and the current date begins to have sensitivity to stoponium around TeV.

R&D; studies on the hadronic calorimeter and physics simulations on the Standard Model and minimal supersymmetric Standard Model Higgs bosons in the CMS experiment

CERN Document Server

Duru, Firdevs

2007-01-01

This thesis consists of two main parts: R&D; studies done on the Compact Muon Solenoid (CMS) Hadronic Calorimeter (HCAL) and physics simulations on the Higgs boson for a Minimal Supersymmetric Standard Model (MSSM) and a Standard Model (SM) channel. In the first part, the air core light guides used in the read-out system of the Hadronic Forward (HF) calorimeter and the reflective materials used in them are studied. Then, tests and simulations were performed to find the most efficient way to collect Cerenkov light from the quartz plates, which are proposed as a substitute for the scintillator tiles in the Hadronic Endcap (HE) calorimeter due to radiation damage problems. In the second part physics simulations and their results are presented. The MSSM channel H/A[arrow right]ττ [arrow right]l l v v v v is studied to investigate the jet and missing transverse energy (MET) reconstruction of the CMS detector. The effects of the jet and MET corrections on the Higgs boson mass reconstruction are investigated. ...

Ruling out a strongly interacting standard Higgs model

International Nuclear Information System (INIS)

Riesselmann, K.; Willenbrock, S.

1997-01-01

Previous work has suggested that perturbation theory is unreliable for Higgs- and Goldstone-boson scattering, at energies above the Higgs-boson mass, for relatively small values of the Higgs quartic coupling λ(μ). By performing a summation of nonlogarithmic terms, we show that perturbation theory is in fact reliable up to relatively large coupling. This eliminates the possibility of a strongly interacting standard Higgs model at energies above the Higgs-boson mass, complementing earlier studies which excluded strong interactions at energies near the Higgs-boson mass. The summation can be formulated in terms of an appropriate scale in the running coupling, μ=√(s)/e∼√(s)/2.7, so it can be incorporated easily in renormalization-group-improved tree-level amplitudes as well as higher-order calculations. copyright 1996 The American Physical Society

Unveiling the Higgs mechanism to students

International Nuclear Information System (INIS)

Organtini, Giovanni

2012-01-01

In this paper we outline a lecture given to undergraduate students to explain why physicists are so interested in the Higgs boson. The lecture was conceived for students not yet familiar with advanced physics and is suitable for those studying several other disciplines. The Higgs mechanism is introduced through semi-classical arguments mimicking basic field-theory concepts, assuming the validity of a symmetry principle in the expression of the energy of particles in a classical field. The lecture is divided into two parts. The first, suitable even for high-school students, shows how the mass of a particle results from a dynamical effect caused by interaction between a massless particle and a field (as in the Higgs mechanism). The audience for the second, much more technical part consists mainly of teachers and university students from disciplines other than physics. (paper)

Finding the CP-violating Higgs bosons at e+e- colliders

International Nuclear Information System (INIS)

Grzadkowski, B.; Gunion, J.F.; Kalinowski, J.

1999-01-01

We discuss a general two-Higgs-doublet model with CP violation in the Higgs sector. In general, the three neutral Higgs fields of the model all mix and the resulting physical Higgs bosons have no definite CP properties. We derive a new sum rule relating Yukawa and Higgs-Z couplings which implies that a neutral Higgs boson cannot escape detection at an e + e - collider if it is kinematically accessible in Z+Higgs boson, b bar b+Higgs boson and t bar t+Higgs boson production, irrespective of the mixing angles and the masses of the other neutral Higgs bosons. We also discuss modifications of the sum rules and their phenomenological consequences in the case when the two-doublet Higgs sector is extended by adding one or more singlets. A brief discussion of the implications of the sum rules for Higgs boson discovery at the Fermilab Tevatron and CERN LHC is given. copyright 1999 The American Physical Society

Trilinear Higgs coupling determination via single-Higgs differential measurements at the LHC

Energy Technology Data Exchange (ETDEWEB)

Maltoni, Fabio; Shivaji, Ambresh; Zhao, Xiaoran [Universite Catholique de Louvain, Centre for Cosmology, Particle Physics and Phenomenology (CP3), Louvain-la-Neuve (Belgium); Pagani, Davide [Technische Universitaet Muenchen, Garching (Germany)

2017-12-15

We study one-loop effects induced by an anomalous Higgs trilinear coupling on total and differential rates for the H → 4l decay and some of the main single-Higgs production channels at the LHC, namely, VBF, VH, t anti tH and tHj. Our results are based on a public code that calculates these effects by simply reweighting samples of Standard-Model-like events for a given production channel. For VH and t anti tH production, where differential effects are particularly relevant, we include Standard Model electroweak corrections, which have similar sizes but different kinematic dependences. Finally, we study the sensitivity of future LHC runs to determine the trilinear coupling via inclusive and differential measurements, considering also the case where the Higgs couplings to vector bosons and the top quark is affected by new physics. We find that the constraints on the couplings and the relevance of differential distributions critically depend on the expected experimental and theoretical uncertainties. (orig.)

Trilinear Higgs coupling determination via single-Higgs differential measurements at the LHC

Science.gov (United States)

Maltoni, Fabio; Pagani, Davide; Shivaji, Ambresh; Zhao, Xiaoran

2017-12-01

We study one-loop effects induced by an anomalous Higgs trilinear coupling on total and differential rates for the H→ 4ℓ decay and some of the main single-Higgs production channels at the LHC, namely, VBF, VH, t{\\bar{t}}H and tHj. Our results are based on a public code that calculates these effects by simply reweighting samples of Standard-Model-like events for a given production channel. For VH and t{\\bar{t}}H production, where differential effects are particularly relevant, we include Standard Model electroweak corrections, which have similar sizes but different kinematic dependences. Finally, we study the sensitivity of future LHC runs to determine the trilinear coupling via inclusive and differential measurements, considering also the case where the Higgs couplings to vector bosons and the top quark is affected by new physics. We find that the constraints on the couplings and the relevance of differential distributions critically depend on the expected experimental and theoretical uncertainties.

The Higgs boson resonance from a chiral Higgs-Yukawa model on the lattice

Energy Technology Data Exchange (ETDEWEB)

Kallarackal, Jim

2011-04-28

Despite the fact that the standard model of particle physics has been confirmed in many high energy experiments, the existence of the Higgs boson is not assured. The Higgs boson is a central part of the electroweak theory and is crucial to generate masses for fermions and the weak gauge bosons. The goal of this work is to set limits on the mass and the decay width of the Higgs boson. The basis to compute the physical quantities is the path integral which is here evaluated by means of Monte Carlo simulations thus allowing for fully non perturbative calculations. A polynomial hybrid Monte Carlo algorithm is used to incorporate dynamical fermions. The chiral symmetry of the electroweak model is incorporated by using the Neuberger overlap operator. Here, the standard model is considered in the limit of a Higgs-Yukawa sector which does not contain the weak gauge bosons and only a degenerate doublet of top- and bottom quarks are incorporated. Results from lattice perturbation theory up to one loop of the Higgs boson propagator are compared with those obtained from Monte Carlo simulations at three different values of the Yukawa coupling. At all values of the investigated couplings, the perturbative results agree very well with the Monte Carlo data. A main focus of this work is the investigation of the resonance parameters of the Higgs boson. The resonance width and the resonance mass are investigated at weak and at large quartic couplings. The parameters of the model are chosen such that the Higgs boson can decay into any even number of Goldstone bosons. Thus, the Higgs boson does not appear as an asymptotic stable state but as a resonance. In all considered cases the Higgs boson resonance width lies below 10% of the resonance mass. The obtained resonance mass is compared with the mass obtained from the Higgs boson propagator. The results agree perfectly at all values of the quartic coupling considered. Finally, the effect of a heavy fourth generation of fermions on the

The Higgs boson resonance from a chiral Higgs-Yukawa model on the lattice

International Nuclear Information System (INIS)

Kallarackal, Jim

2011-01-01

Despite the fact that the standard model of particle physics has been confirmed in many high energy experiments, the existence of the Higgs boson is not assured. The Higgs boson is a central part of the electroweak theory and is crucial to generate masses for fermions and the weak gauge bosons. The goal of this work is to set limits on the mass and the decay width of the Higgs boson. The basis to compute the physical quantities is the path integral which is here evaluated by means of Monte Carlo simulations thus allowing for fully non perturbative calculations. A polynomial hybrid Monte Carlo algorithm is used to incorporate dynamical fermions. The chiral symmetry of the electroweak model is incorporated by using the Neuberger overlap operator. Here, the standard model is considered in the limit of a Higgs-Yukawa sector which does not contain the weak gauge bosons and only a degenerate doublet of top- and bottom quarks are incorporated. Results from lattice perturbation theory up to one loop of the Higgs boson propagator are compared with those obtained from Monte Carlo simulations at three different values of the Yukawa coupling. At all values of the investigated couplings, the perturbative results agree very well with the Monte Carlo data. A main focus of this work is the investigation of the resonance parameters of the Higgs boson. The resonance width and the resonance mass are investigated at weak and at large quartic couplings. The parameters of the model are chosen such that the Higgs boson can decay into any even number of Goldstone bosons. Thus, the Higgs boson does not appear as an asymptotic stable state but as a resonance. In all considered cases the Higgs boson resonance width lies below 10% of the resonance mass. The obtained resonance mass is compared with the mass obtained from the Higgs boson propagator. The results agree perfectly at all values of the quartic coupling considered. Finally, the effect of a heavy fourth generation of fermions on the

From the Higgs boson to the search for new physics: the prospects for the LHC programme at CERN

CERN Multimedia

CERN. Geneva

2013-01-01

The discovery of the Higgs boson, which was the subject of this year's Nobel prize for physics, has brought us the missing piece of the Standard Model of Particle Physics.  However, many observations (such as the predominance of matter over antimatter in the Universe, the existence of dark matter observed by the cosmologists and even the fact that the Higgs boson has a relatively small mass) underline that our knowledge of the structure of matter and its interactions is incomplete.   A wide-ranging programme of research spanning several decades to come thus awaits us at the LHC.  Philippe Bloch will begin his lecture by giving us the latest news on the Higgs boson, and will then go on to explain how developments at the LHC and its experiments, which will resume in 2015, will explore these fund...

Exciting the Vacuum: Possible Manifestations of the Higgs Particle at the LHC

International Nuclear Information System (INIS)

Kaplan, David

2009-01-01

The Higgs boson is the particle most anticipated at the LHC. However, there is currently no leading theory of electroweak symmetry breaking (and the 'Higgs mechanism'). The many possibilities suggest many ways the Higgs could appear in the detectors, some of which require non-standard search methods. I will review the current state of beyond the standard model physics and the implication for Higgs physics. I then discuss some non-standard Higgs decays and suggest (perhaps naive) new experimental strategies for detecting the Higgs in such cases. In some models, while part of the new physics at the weak scale would be visible, the Higgs would be nearly impossible to detect.

Search for BSM Higgs bosons in fermion decay modes with ATLAS

CERN Document Server

Straessner, Arno; The ATLAS collaboration

2017-01-01

Many physics models beyond the Standard Model (BSM) predict an extension of the Higgs sector, like the general 2-Higgs Doublet Model (2HDM) or supersymmetric models. In case of one additional Higgs doublet, there are five physical Higgs bosons: two CP neutral states (h,H), one CP odd state (A) and two charged Higgs bosons (H±). Typically, the already observed Higgs boson is identified with the h Higgs boson, while the others are assumed to be heavy. This presentation is reporting on recent results of direct searches for heavy neutral and charged Higgs bosons by the ATLAS Collaboration, in particular analyzing direct Higgs boson decays to fermions, like $H^\\pm \\to \\tau\

Implications of new physics for Higgs searches at the LHC

International Nuclear Information System (INIS)

Albornoz Vasquez, D.; Arbey, A.; Battaglia, M.; Belanger, G.; Belyaev, A.; Boehm, C.; Boudjema, F.; Brown, M.; Da Silva, J.; Djouadi, A.; Drieu La Rochelle, G.; Dumont, B.; Godbole, R.; Kakizaki, M.; Kraml, S.; Mahmoudi, F.; Pukhov, A.; Sekmen, S.; Wingerter, A.; Wymant, C.

2012-01-01

We examine to what extent the Higgs sectors of extensions of the Standard Model (SM) are constrained on the one hand by the LHC searches for the SM Higgs boson, on the other hand by LHC searches for new particles beyond the SM. The models considered include the MSSM (Minimal Supersymmetric Standard Model) and some of its extensions, as well as a minimal UED (Universal Extra Dimensions) model and the SM with a sequential 4. generation. Among other issues, we discuss expectations for the signal strength of a light Higgs in the γγ channel in these models. Where relevant we discuss also the WW/ZZ channels. Moreover, we assess the implications of the recent hints of a Higgs signal at the LHC corresponding to a Higgs mass near 125 GeV. (authors)

Beyond-the-Standard Model Higgs Physics using the ATLAS Experiment

CERN Document Server

AUTHOR|(INSPIRE)INSPIRE-00444174; The ATLAS collaboration

2015-01-01

Some recent searches for the Higgs boson in the context of beyond the Standard Model, performed by the ATLAS experiment are presented: high mass Higgs boson searches, lepton flavour violating Higgs decay, NMSSM, con- straint from the search for three photons. The interpretation based on the measurements of Higgs couplings are shown, along with the constraint on the Higgs boson invisible decays. Except the latter has some part using both full √s = 7 TeV and √s = 8 TeV data, the rest are performed with the √s = 8 TeV data of proton-proton collisions collected by the ATLAS experiment. No sig- nificant excess of data over the predicted background is observed in all those searches. Limits are placed in certain quantities depending on the searches.

Disentangling a dynamical Higgs

International Nuclear Information System (INIS)

Brivio, I.; Corbett, T.; Éboli, O.J.P.; Gavela, M.B.; Gonzalez-Fraile, J.; Gonzalez-Garcia, M.C.; Merlo, L.; Rigolin, S.

2014-01-01

The pattern of deviations from Standard Model predictions and couplings is different for theories of new physics based on a non-linear realization of the SU(2) L ×U(1) Y gauge symmetry breaking and those assuming a linear realization. We clarify this issue in a model-independent way via its effective Lagrangian formulation in the presence of a light Higgs particle, up to first order in the expansions: dimension-six operators for the linear expansion and four derivatives for the non-linear one. Complete sets of gauge and gauge-Higgs operators are considered, implementing the renormalization procedure and deriving the Feynman rules for the non-linear expansion. We establish the theoretical relation and the differences in physics impact between the two expansions. Promising discriminating signals include the decorrelation in the non-linear case of signals correlated in the linear one: some pure gauge versus gauge-Higgs couplings and also between couplings with the same number of Higgs legs. Furthermore, anomalous signals expected at first order in the non-linear realization may appear only at higher orders of the linear one, and vice versa. We analyze in detail the impact of both type of discriminating signals on LHC physics

Disentangling a dynamical Higgs

Energy Technology Data Exchange (ETDEWEB)

Brivio, I. [Departamento de Física Teórica and Instituto de Física Teórica, IFT-UAM/CSIC,Universidad Autónoma de Madrid, Cantoblanco, 28049, Madrid (Spain); Corbett, T. [C.N. Yang Institute for Theoretical Physics and Department of Physics and Astronomy,SUNY at Stony Brook, Stony Brook, NY 11794-3840 (United States); Éboli, O.J.P. [Instituto de Física, Universidade de São Paulo,C.P. 66318, 05315-970, São Paulo SP (Brazil); Gavela, M.B. [Departamento de Física Teórica and Instituto de Física Teórica, IFT-UAM/CSIC,Universidad Autónoma de Madrid, Cantoblanco, 28049, Madrid (Spain); Gonzalez-Fraile, J. [Departament d’Estructura i Constituents de la Matèria and ICC-UB, Universitat de Barcelona,647 Diagonal, E-08028 Barcelona (Spain); Gonzalez-Garcia, M.C. [Institució Catalana de Recerca i Estudis Avançats (ICREA),Passeig Lluís Companys, 23, E-08010 Barcelona (Spain); Departament d’Estructura i Constituents de la Matèria and ICC-UB, Universitat de Barcelona,647 Diagonal, E-08028 Barcelona (Spain); C.N. Yang Institute for Theoretical Physics and Department of Physics and Astronomy,SUNY at Stony Brook, Stony Brook, NY 11794-3840 (United States); Merlo, L. [Departamento de Física Teórica and Instituto de Física Teórica, IFT-UAM/CSIC,Universidad Autónoma de Madrid, Cantoblanco, 28049, Madrid (Spain); Rigolin, S. [Dipartimento di Fisica e Astronomia “G. Galilei”, Università di Padova and INFN, Sezione di Padova, Via Marzolo 8, I-35131 Padua (Italy)

2014-03-05

The pattern of deviations from Standard Model predictions and couplings is different for theories of new physics based on a non-linear realization of the SU(2){sub L}×U(1){sub Y} gauge symmetry breaking and those assuming a linear realization. We clarify this issue in a model-independent way via its effective Lagrangian formulation in the presence of a light Higgs particle, up to first order in the expansions: dimension-six operators for the linear expansion and four derivatives for the non-linear one. Complete sets of gauge and gauge-Higgs operators are considered, implementing the renormalization procedure and deriving the Feynman rules for the non-linear expansion. We establish the theoretical relation and the differences in physics impact between the two expansions. Promising discriminating signals include the decorrelation in the non-linear case of signals correlated in the linear one: some pure gauge versus gauge-Higgs couplings and also between couplings with the same number of Higgs legs. Furthermore, anomalous signals expected at first order in the non-linear realization may appear only at higher orders of the linear one, and vice versa. We analyze in detail the impact of both type of discriminating signals on LHC physics.

Higgs pair production at NLO QCD for CP-violating Higgs sectors

Science.gov (United States)

Gröber, R.; Mühlleitner, M.; Spira, M.

2017-12-01

Higgs pair production through gluon fusion is an important process at the LHC to test the dynamics underlying electroweak symmetry breaking. Higgs sectors beyond the Standard Model (SM) can substantially modify this cross section through novel couplings not present in the SM or the on-shell production of new heavy Higgs bosons that subsequently decay into Higgs pairs. CP violation in the Higgs sector is important for the explanation of the observed matter-antimatter asymmetry through electroweak baryogenesis. In this work we compute the next-to-leading order (NLO) QCD corrections in the heavy top quark limit, including the effects of CP violation in the Higgs sector. We choose the effective theory (EFT) approach, which provides a rather model-independent way to explore New Physics (NP) effects by adding dimension-6 operators, both CP-conserving and CP-violating ones, to the SM Lagrangian. Furthermore, we perform the computation within a specific UV-complete model and choose as benchmark model the general 2-Higgs-Doublet Model with CP violation, the C2HDM. Depending on the dimension-6 coefficients, the relative NLO QCD corrections are affected by several per cent through the new CP-violating operators. This is also the case for SM-like Higgs pair production in the C2HDM, while the relative QCD corrections in the production of heavier C2HDM Higgs boson pairs deviate more strongly from the SM case. The absolute cross sections both in the EFT and the C2HDM can be modified by more than an order of magnitude. In particular, in the C2HDM the resonant production of Higgs pairs can by far exceed the SM cross section.

Lecture at the Globe | "From the Higgs boson to the search for new physics: the prospects for the LHC programme at CERN"

CERN Multimedia

2013-01-01

Christmas lecture (in French, with simultaneous interpreting into English): "From the Higgs boson to the search for new physics: the prospects for the LHC programme at CERN", by Philippe Bloch.   Globe of Science and Innovation Route de Meyrin, 1211 Genève Monday 16 December 2013 at 8:30 p.m. The discovery of the Higgs boson, which was the subject of this year's Nobel prize for physics, has brought us the missing piece of the Standard Model of particle physics. However, many observations (such as the predominance of matter over antimatter in the Universe, the existence of dark matter observed by cosmologists and even the fact that the Higgs boson has a relatively small mass) underline that our knowledge of the structure of matter and its interactions is incomplete.   A wide-ranging programme of research spanning several decades to come thus awaits us at the LHC. Philippe Bloch will begin his lecture by giving us the latest news on the Higg...

Higgs bosons in the left-right model

International Nuclear Information System (INIS)

Boyarkina, G.G.; Boyarkin, O.M.

2000-01-01

The model with the SU(2) L x SU(2) R x U(1) B-L gauge group, containing one bidoublet and two triplets in the Higgs sector, is considered. The link between the constants determining the physical Higgs boson interactions and the neutrino oscillation parameters is found. It is shown that the observation of the ultrahigh-energy neutrinos with the help of the processes e - ν e →W - Z, e - ν e →μ - ν μ , gives us information on the singly charged Higgs bosons. The processes of the doubly charged Higgs boson production, e - μ - →Δ (--) 1 γ, e - μ - →Δ (--) 1 Z, are investigated. From the point of view of detecting the neutral Higgs bosons the process of the electron-muon recharge e - μ + →e + μ - is studied. (orig.)

Higgs Boson Properties and Search for Additional Resonances

CERN Document Server

AUTHOR|(INSPIRE)INSPIRE-00435709

The Higgs boson was predicted by the Standard Model of particle physics and jointly discovered by the CMS and ATLAS experiments at LHC, in 2012. Following its discovery, the property measurements of the Higgs boson and the search for additional resonances become important research goals. The Standard Model is not the complete theory and leaves many questions unanswered, therefore it is important to search for any evidence of new physics beyond the SM. This thesis will briefly introduce the theoretical motivation for the Higgs boson, the production and decay mechanisms of the Higgs boson, and the methods used for analysis of the Higgs boson properties. The spin-1 and spin-2 Higgs hypotheses are tested in H->ZZ->4l channel, using the data recorded by CMS in Run1 of LHC. The exotic spin models were excluded and the Higgs boson is shown to agree with the Standard Model prediction of spin-0. The search for high-mass Higgs-like resonance is performed in H->ZZ->4l and H->ZZ->2l2q channels, using data recorded by CMS...

Prospecting for new physics in the Higgs and flavor sectors

International Nuclear Information System (INIS)

Bishara, Fady

2015-01-01

We explore two directions in beyond the standard model physics: dark matter model building and probing new sources of CP violation. In dark matter model building, we consider two scenarios where the stability of dark matter derives from the flavor symmetries of the standard model. The first model contains a flavor singlet dark matter candidate whose couplings to the visible sector are proportional to the flavor breaking parameters. This leads to a metastable dark matter with TeV scale mediators. In the second model, we consider a fully gauged SU(3) 3 flavor model with a flavor triplet dark matter. Consequently, the dark matter multiplet is charged while the standard model fields are neutral under a remnant Z 3 which ensures dark matter stability. We show that a Dirac fermion dark matter with radiative splitting in the multiplet must have a mass in the range [0:5; 5] TeV in order to satisfy all experimental constraints. We then turn our attention to Higgs portal dark matter and investigate the possibility of obtaining bounds on the up, down, and strange quark Yukawa couplings. If Higgs portal dark matter is discovered, we find that direct detection rates are insensitive to vanishing light quark Yukawa couplings. We then review flavor models and give the expected enhancement or suppression of the Yukawa couplings in those models. Finally, in the last two chapters, we develop techniques for probing CP violation in the Higgs coupling to photons and in rare radiative decays of B mesons. While theoretically clean, we find that these methods are not practical with current and planned detectors. However, these techniques can be useful with a dedicated detector (e.g., a gaseous TPC). In the case of radiative B meson decay B 0 → (K* → Kππ)γ, the techniques we develop also allow the extraction of the photon polarization fraction which is sensitive to new physics contributions since, in the standard model, the right(left) handed polarization fraction is of O(Λ QCD =m b

Frequently Asked Questions: The Higgs!

CERN Multimedia

CERN Bulletin

2012-01-01

Why have we tried so hard to find the Higgs particle? How does the Higgs mechanism work? What is the difference in physics between strong evidence and a discovery? Why do physicists speak in terms of "sigmas"? Find out here!   Why have we tried so hard to find the Higgs particle? Because it could be the answer to the question: how does Nature decide whether or not to assign mass to particles? All the fundamental particles making up matter – the electron, the quarks, etc. – have masses. Moreover, quantum physics requires that forces are also carried by particles. The W and Z particles that carry the weak force responsible for radioactivity must also have masses, whereas the photon, the carrier of the electromagnetic force, has no mass at all. This is the root of the “Higgs problem”: how to give masses to the fundamental particles and break the symmetry between the massive W and Z and the massless photon? Just assigning masses by hand...

B-meson anomalies and Higgs physics in flavored U(1)' model

Science.gov (United States)

Bian, Ligong; Lee, Hyun Min; Park, Chan Beom

2018-04-01

We consider a simple extension of the Standard Model with flavor-dependent U(1)', that has been proposed to explain some of B-meson anomalies recently reported at LHCb. The U(1)' charge is chosen as a linear combination of anomaly-free B_3-L_3 and L_μ -L_τ . In this model, the flavor structure in the SM is restricted due to flavor-dependent U(1)' charges, in particular, quark mixings are induced by a small vacuum expectation value of the extra Higgs doublet. As a result, it is natural to get sizable flavor-violating Yukawa couplings of heavy Higgs bosons involving the bottom quark. In this article, we focus on the phenomenology of the Higgs sector of the model including extra Higgs doublet and singlet scalars. We impose various bounds on the extended Higgs sector from Higgs and electroweak precision data, B-meson mixings and decays as well as unitarity and stability bounds, then discuss the productions and decays of heavy Higgs bosons at the LHC.

Higgs pair production at NLO QCD for CP-violating Higgs sectors

Directory of Open Access Journals (Sweden)

R. Gröber

2017-12-01

Full Text Available Higgs pair production through gluon fusion is an important process at the LHC to test the dynamics underlying electroweak symmetry breaking. Higgs sectors beyond the Standard Model (SM can substantially modify this cross section through novel couplings not present in the SM or the on-shell production of new heavy Higgs bosons that subsequently decay into Higgs pairs. CP violation in the Higgs sector is important for the explanation of the observed matter-antimatter asymmetry through electroweak baryogenesis. In this work we compute the next-to-leading order (NLO QCD corrections in the heavy top quark limit, including the effects of CP violation in the Higgs sector. We choose the effective theory (EFT approach, which provides a rather model-independent way to explore New Physics (NP effects by adding dimension-6 operators, both CP-conserving and CP-violating ones, to the SM Lagrangian. Furthermore, we perform the computation within a specific UV-complete model and choose as benchmark model the general 2-Higgs-Doublet Model with CP violation, the C2HDM. Depending on the dimension-6 coefficients, the relative NLO QCD corrections are affected by several per cent through the new CP-violating operators. This is also the case for SM-like Higgs pair production in the C2HDM, while the relative QCD corrections in the production of heavier C2HDM Higgs boson pairs deviate more strongly from the SM case. The absolute cross sections both in the EFT and the C2HDM can be modified by more than an order of magnitude. In particular, in the C2HDM the resonant production of Higgs pairs can by far exceed the SM cross section.

Large mass of the littlest Higgs boson

International Nuclear Information System (INIS)

Bazzocchi, F.; Fabbrichesi, M.; Piai, M.

2005-01-01

We study the exact (one-loop) effective potential of the littlest Higgs model and determine the dependence of physical quantities, such as the vacuum expectation value v W and mass m h of the Higgs boson, on the fundamental parameters of the Lagrangian--masses, couplings of new states, the fundamental scale f of the sigma model, and the coefficients of operators quadratically sensitive to the cutoff of the theory. On the one hand, we show that it is possible to have the electroweak ground state and a relatively large cutoff Λ=4πf with f in the 2 TeV range without requiring unnaturally small coefficients for quadratically divergent quantities, and with only moderate cancellations between the contribution of different sectors to the effective potential of the Higgs. On the other hand, this cannot be achieved while at the same time keeping m h close to its current lower bound of 114.4 GeV. The natural expectation for m h is O(f), mainly because of large logarithmically divergent contributions to the effective potential of the top-quark sector. Even a fine-tuning at the level of O(10 -2 ) in the coefficients of the quadratic divergences is not enough to produce small physical Higgs masses, and the natural expectation is in the 800 GeV range for f∼2 TeV. We conclude that the littlest Higgs model is a solution of the little hierarchy problem, in the sense that it stabilizes the electroweak symmetry breaking scale to be a factor of 100 less than the cutoff of the theory, but this requires a quite large physical mass for the Higgs, and hence precision electroweak studies should be redone accordingly. We also study finite temperature corrections. The first order electroweak phase transition is no stronger than in the standard model. A second phase transition (nonrestoration of symmetry at high temperature) depends strongly on the logarithmic terms in the potential

The Higgs portal above threshold

Energy Technology Data Exchange (ETDEWEB)

Craig, Nathaniel [Department of Physics, University of California,Santa Barbara, CA 93106 (United States); Lou, Hou Keong [Department of Physics, Princeton University,Princeton, NJ 08540 (United States); McCullough, Matthew [Theory Division, CERN,1211 Geneva 23 (Switzerland); Thalapillil, Arun [Department of Physics and Astronomy, Rutgers University,Piscataway, NJ 08854 (United States)

2016-02-18

The discovery of the Higgs boson opens the door to new physics interacting via the Higgs Portal, including motivated scenarios relating to baryogenesis, dark matter, and electroweak naturalness. We systematically explore the collider signatures of singlet scalars produced via the Higgs Portal at the 14 TeV LHC and a prospective 100 TeV hadron collider. We focus on the challenging regime where the scalars are too heavy to be produced in the decays of an on-shell Higgs boson, and instead are produced primarily via an off-shell Higgs. Assuming these scalars escape the detector, promising channels include missing energy in association with vector boson fusion, monojets, and top pairs. We forecast the sensitivity of searches in these channels at √s=14 & 100 TeV and compare collider reach to the motivated parameter space of singlet-assisted electroweak baryogenesis, Higgs Portal dark matter, and neutral naturalness.

The Higgs portal above threshold

International Nuclear Information System (INIS)

Craig, Nathaniel; Lou, Hou Keong; McCullough, Matthew; Thalapillil, Arun

2016-01-01

The discovery of the Higgs boson opens the door to new physics interacting via the Higgs Portal, including motivated scenarios relating to baryogenesis, dark matter, and electroweak naturalness. We systematically explore the collider signatures of singlet scalars produced via the Higgs Portal at the 14 TeV LHC and a prospective 100 TeV hadron collider. We focus on the challenging regime where the scalars are too heavy to be produced in the decays of an on-shell Higgs boson, and instead are produced primarily via an off-shell Higgs. Assuming these scalars escape the detector, promising channels include missing energy in association with vector boson fusion, monojets, and top pairs. We forecast the sensitivity of searches in these channels at √s=14 & 100 TeV and compare collider reach to the motivated parameter space of singlet-assisted electroweak baryogenesis, Higgs Portal dark matter, and neutral naturalness.

New ideas for effective Higgs measurements

Energy Technology Data Exchange (ETDEWEB)

Brehmer, Johann

2017-07-26

An effective field theory provides a model-independent and phenomenologically powerful parametrisation of new physics in the Higgs sector. We analyse two aspects of this framework that are relevant for measurements of the Higgs properties during Run 2 of the LHC. First, the limited precision of the LHC analyses cannot guarantee a clear hierarchy between the experimental momentum transfer and the probed new physics scales, casting doubt on the validity of the effective model. By comparing a range of new physics scenarios to their dimension-six approximation, we analyse if an effective description of the Higgs sector is useful, where it breaks down, and how its validity can be improved. Second, we use information geometry to understand and optimise Higgs measurements at the LHC. Our novel approach is based on the Fisher information, which encodes the maximum precision with which theory parameters can be measured in an experiment. We develop an algorithm to calculate the Fisher information in LHC processes and compute the information on dimension-six operators in different Higgs signatures. We demonstrate how information geometry lets us improve event selections, determine the most powerful observables, and compare the power of modern multivariate techniques to that of traditional histogram-based analyses.

New ideas for effective Higgs measurements

International Nuclear Information System (INIS)

Brehmer, Johann

2017-01-01

An effective field theory provides a model-independent and phenomenologically powerful parametrisation of new physics in the Higgs sector. We analyse two aspects of this framework that are relevant for measurements of the Higgs properties during Run 2 of the LHC. First, the limited precision of the LHC analyses cannot guarantee a clear hierarchy between the experimental momentum transfer and the probed new physics scales, casting doubt on the validity of the effective model. By comparing a range of new physics scenarios to their dimension-six approximation, we analyse if an effective description of the Higgs sector is useful, where it breaks down, and how its validity can be improved. Second, we use information geometry to understand and optimise Higgs measurements at the LHC. Our novel approach is based on the Fisher information, which encodes the maximum precision with which theory parameters can be measured in an experiment. We develop an algorithm to calculate the Fisher information in LHC processes and compute the information on dimension-six operators in different Higgs signatures. We demonstrate how information geometry lets us improve event selections, determine the most powerful observables, and compare the power of modern multivariate techniques to that of traditional histogram-based analyses.

A global view on the Higgs self-coupling

International Nuclear Information System (INIS)

Di Vita, S.; Grojean, C.; Humboldt-Universitaet, Berlin; Panico, G.; Riembau, M.; Vantalon, T.; Barcelona Institute of Science and Technology, Bellaterra

2017-04-01

The Higgs self-coupling is notoriously intangible at the LHC. It was recently proposed to probe the trilinear Higgs interaction through its radiative corrections to single-Higgs processes. This approach however requires to disentangle these effects from those associated to deviations of other Higgs-couplings to fermions and gauge bosons. We show that a global fit exploiting only single-Higgs inclusive data suffers from degeneracies that prevent one from extracting robust bounds on each individual coupling. We show how the inclusion of double-Higgs production via gluon fusion, and the use of differential measurements in the associated single-Higgs production channels WH, ZH and t anti tH, can help to overcome the deficiencies of a global Higgs-couplings fit. In particular, we bound the variations of the Higgs trilinear self-coupling relative to its SM value to the interval [0.1, 2.3] at 68% confidence level at the high-luminosity LHC, and we discuss the robustness of our results against various assumptions on the experimental uncertainties and the underlying new physics dynamics. We also study how to obtain a parametrically enhanced deviation of the Higgs self-couplings and we estimate how large this deviation can be in a self-consistent effective field theory framework.

A global view on the Higgs self-coupling

Energy Technology Data Exchange (ETDEWEB)

Di Vita, S. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Grojean, C. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Panico, G. [Barcelona Institute of Science and Technology, Bellaterra (Spain). IFAE; Riembau, M.; Vantalon, T. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Barcelona Institute of Science and Technology, Bellaterra (Spain). IFAE

2017-04-15

The Higgs self-coupling is notoriously intangible at the LHC. It was recently proposed to probe the trilinear Higgs interaction through its radiative corrections to single-Higgs processes. This approach however requires to disentangle these effects from those associated to deviations of other Higgs-couplings to fermions and gauge bosons. We show that a global fit exploiting only single-Higgs inclusive data suffers from degeneracies that prevent one from extracting robust bounds on each individual coupling. We show how the inclusion of double-Higgs production via gluon fusion, and the use of differential measurements in the associated single-Higgs production channels WH, ZH and t anti tH, can help to overcome the deficiencies of a global Higgs-couplings fit. In particular, we bound the variations of the Higgs trilinear self-coupling relative to its SM value to the interval [0.1, 2.3] at 68% confidence level at the high-luminosity LHC, and we discuss the robustness of our results against various assumptions on the experimental uncertainties and the underlying new physics dynamics. We also study how to obtain a parametrically enhanced deviation of the Higgs self-couplings and we estimate how large this deviation can be in a self-consistent effective field theory framework.

Search for rare and exotic Higgs Boson decay modes and Higgs Boson pair production with the ATLAS detector

CERN Document Server

Tong, Baojia; The ATLAS collaboration

2018-01-01

An enhanced production of double Higgs bosons or exotic decays of the Higgs boson would be two clear signs of beyond Standard Model physics. A search is performed for resonant and non-resonant Higgs boson pair production, where the two Higgs bosons decay to four bottom quarks. Another search is conducted for a Higgs boson decay to XX to four leptons. Both analyses use up to 36 ifb of p-p collision data collected by the ATLAS detector at 13 TeV. No significant excess is found. The observed 95% confidence level upper limit on the non-resonant Higgs boson pair production is 13 times the Standard Model prediction.

Model-independent determination of the triple Higgs coupling at e+e- colliders

Science.gov (United States)

Barklow, Tim; Fujii, Keisuke; Jung, Sunghoon; Peskin, Michael E.; Tian, Junping

2018-03-01

The observation of Higgs pair production at high-energy colliders can give evidence for the presence of a triple Higgs coupling. However, the actual determination of the value of this coupling is more difficult. In the context of general models for new physics, double Higgs production processes can receive contributions from many possible beyond-Standard-Model effects. This dependence must be understood if one is to make a definite statement about the deviation of the Higgs field potential from the Standard Model. In this paper, we study the extraction of the triple Higgs coupling from the process e+e-→Z h h . We show that, by combining the measurement of this process with other measurements available at a 500 GeV e+e- collider, it is possible to quote model-independent limits on the effective field theory parameter c6 that parametrizes modifications of the Higgs potential. We present precise error estimates based on the anticipated International Linear Collider physics program, studied with full simulation. Our analysis also gives new insight into the model-independent extraction of the Higgs boson coupling constants and total width from e+e- data.

The limit of the Yang-Mills-Higgs flow on Higgs bundles

OpenAIRE

Li, Jiayu; Zhang, Xi

2014-01-01

In this paper, we consider the gradient flow of the Yang-Mills-Higgs functional for Higgs pairs on a Hermitian vector bundle $(E, H_{0})$ over a compact K\\"ahler manifold $(M, \\omega )$. We study the asymptotic behavior of the Yang-Mills-Higgs flow for Higgs pairs at infinity, and show that the limiting Higgs sheaf is isomorphic to the double dual of the graded Higgs sheaves associated to the Harder-Narasimhan-Seshadri filtration of the initial Higgs bundle.

Higgs searches and prospects at CDF

International Nuclear Information System (INIS)

Pavel A Murat

2003-01-01

The Standard model of electroweak interactions (SM) has been extremely successful in describing interactions of elementary particles over the last decades. The Higgs scalar boson is one of the key elements of the SM: Higgs interactions with the other particles generate the particle masses and allow to keep the theory renormalizable at electroweak scale. All the particles predicted by the SM but the Higgs boson have already been observed experimentally and therefore search for the Higgs is one of the most important scientific goals for high energy physics. The current lower limit on the SM Higgs mass M H > 114.4 GeV at 95% CL has been established by LEP experiments. In this paper we review CDF Run I results on Higgs searches including the Higgs bosons predicted by the minimal supersymmetric extention of the Standard Model (MSSM) and discuss the Run II prospects

90 - GeV Higgs boson in supersymmetric models

International Nuclear Information System (INIS)

Grzadkowski, B.; Kalinowski, J.; Pokorski, S.

1989-07-01

We discuss supersymmetric models with a hierarchy of vacuum expectation values of Higgs fields. These models predict one of the physical neutral Higgs bosons to have its mass very close to the Z-boson mass. Properties of such a 90-GeV Higgs boson are discussed. (author)

Challenges for MSSM Higgs searches at hadron colliders

Energy Technology Data Exchange (ETDEWEB)

Carena, Marcela S.; /Fermilab; Menon, A.; /Argonne /Chicago U., EFI; Wagner, C.E.M.; /Argonne /Chicago U., EFI /KICP, Chicago /Chicago U.

2007-04-01

In this article we analyze the impact of B-physics and Higgs physics at LEP on standard and non-standard Higgs bosons searches at the Tevatron and the LHC, within the framework of minimal flavor violating supersymmetric models. The B-physics constraints we consider come from the experimental measurements of the rare B-decays b {yields} s{gamma} and B{sub u} {yields} {tau}{nu} and the experimental limit on the B{sub s} {yields} {mu}{sup +}{mu}{sup -} branching ratio. We show that these constraints are severe for large values of the trilinear soft breaking parameter A{sub t}, rendering the non-standard Higgs searches at hadron colliders less promising. On the contrary these bounds are relaxed for small values of A{sub t} and large values of the Higgsino mass parameter {mu}, enhancing the prospects for the direct detection of non-standard Higgs bosons at both colliders. We also consider the available ATLAS and CMS projected sensitivities in the standard model Higgs search channels, and we discuss the LHC's ability in probing the whole MSSM parameter space. In addition we also consider the expected Tevatron collider sensitivities in the standard model Higgs h {yields} b{bar b} channel to show that it may be able to find 3 {sigma} evidence in the B-physics allowed regions for small or moderate values of the stop mixing parameter.

Charged Higgs boson searches and SemiConductor Tracker commissioning for the ATLAS experiment

CERN Document Server

Mohn, Bjarte Alsaker

The ATLAS (A Toroidal Lhc ApparatuS) experiment is one of four major experiments presently being installed at the upcoming Large Hadron Collider (LHC) at the European Centre for Nuclear Research (CERN) outside Geneva. In this thesis we present work done on both the simulation of the ATLAS physics potential for a charged Higgs boson and the construction of the Semiconductor Tracker (SCT) - a subdetector within the ATLAS Inner Detector. The discovery of a charged Higgs boson would be an unambiguous sign of physics beyond the Standard Model (SM) and it is thus of great interest to study the ATLAS potential for a charged Higgs discovery. Two such studies have been conducted for this thesis. In the first study a large-mass-splitting Minimal Supersymmetric Standard Model (MSSM) is assumed in which the charged Higgs boson decays into a W boson and a neutral Higgs may receive a large branching ratio.We conclude, however, that charged Higgs searches in this decay channel are made difficult by a large irreducible SM ba...

Very light dilaton and naturally light Higgs boson

Science.gov (United States)

Hong, Deog Ki

2018-02-01

We study very light dilaton, arising from a scale-invariant ultraviolet theory of the Higgs sector in the standard model of particle physics. Imposing the scale symmetry below the ultraviolet scale of the Higgs sector, we alleviate the fine-tuning problem associated with the Higgs mass. When the electroweak symmetry is spontaneously broken radiatively à la Coleman-Weinberg, the dilaton develops a vacuum expectation value away from the origin to give an extra contribution to the Higgs potential so that the Higgs mass becomes naturally around the electroweak scale. The ultraviolet scale of the Higgs sector can be therefore much higher than the electroweak scale, as the dilaton drives the Higgs mass to the electroweak scale. We also show that the light dilaton in this scenario is a good candidate for dark matter of mass m D ˜ 1 eV - 10 keV, if the ultraviolet scale is about 10-100 TeV. Finally we propose a dilaton-assisted composite Higgs model to realize our scenario. In addition to the light dilaton the model predicts a heavy U(1) axial vector boson and two massive, oppositely charged, pseudo Nambu-Goldstone bosons, which might be accessible at LHC.

Minimal composite Higgs models at the LHC

Science.gov (United States)

Carena, Marcela; Da Rold, Leandro; Pontón, Eduardo

2014-06-01

We consider composite Higgs models where the Higgs is a pseudo-Nambu Goldstone boson arising from the spontaneous breaking of an approximate global symmetry by some underlying strong dynamics. We focus on the SO(5) → SO(4) symmetry breaking pattern, assuming the "partial compositeness" paradigm. We study the consequences on Higgs physics of the fermionic representations produced by the strong dynamics, that mix with the Standard Model (SM) degrees of freedom. We consider models based on the lowest-dimensional representations of SO(5) that allow for the custodial protection of the coupling, i.e. the 5, 10 and 14. We find a generic suppression of the gluon fusion process, while the Higgs branching fractions can be enhanced or suppressed compared to the SM. Interestingly, a precise measurement of the Higgs boson couplings can distinguish between different realizations in the fermionic sector, thus providing crucial information about the nature of the UV dynamics.

Minimal composite Higgs models at the LHC

International Nuclear Information System (INIS)

Carena, Marcela; Rold, Leandro Da; Pontón, Eduardo

2014-01-01

We consider composite Higgs models where the Higgs is a pseudo-Nambu Goldstone boson arising from the spontaneous breaking of an approximate global symmetry by some underlying strong dynamics. We focus on the SO(5)→SO(4) symmetry breaking pattern, assuming the “partial compositeness" paradigm. We study the consequences on Higgs physics of the fermionic representations produced by the strong dynamics, that mix with the Standard Model (SM) degrees of freedom. We consider models based on the lowest-dimensional representations of SO(5) that allow for the custodial protection of the Zb-barb coupling, i.e. the 5, 10 and 14. We find a generic suppression of the gluon fusion process, while the Higgs branching fractions can be enhanced or suppressed compared to the SM. Interestingly, a precise measurement of the Higgs boson couplings can distinguish between different realizations in the fermionic sector, thus providing crucial information about the nature of the UV dynamics.

Effective Field Theory with Two Higgs Doublets

CERN Document Server

Crivellin, Andreas; Procura, Massimiliano

2016-01-01

In this article we extend the effective field theory framework describing new physics effects to the case where the underlying low-energy theory is a Two-Higgs-Doublet model. We derive a complete set of independent operators up to dimension six assuming a $Z_2$-invariant CP-conserving Higgs potential. The effects on Higgs and gauge boson masses, mixing angles in the Higgs sector as well as couplings to fermions and gauge bosons are computed. At variance with the case of a single Higgs doublet, we find that pair production of SM-like Higgses, arising through dimension-six operators, is not fixed by fermion-fermion-Higgs couplings and can therefore be sizable.

Higgs characterisation in the presence of theoretical uncertainties and invisible decays

Energy Technology Data Exchange (ETDEWEB)

Englert, Christoph [University of Glasgow, SUPA, School of Physics and Astronomy, Glasgow (United Kingdom); Kogler, Roman [Universitaet Hamburg, Institut fuer Experimentalphysik, Hamburg (Germany); Schulz, Holger; Spannowsky, Michael [Durham University, Department of Physics, Institute for Particle Physics Phenomenology, Durham (United Kingdom)

2017-11-15

While the Higgs characterisation programme is well under way, direct signs for new physics beyond the Standard Model remain elusive. Performing a fit of fully differential Higgs production cross sections at the LHC to a subset of Higgs-relevant effective operators, we discuss the extent to which theoretical uncertainties can limit the sensitivity in such a new physics search programme. Extending the dimension-6 Higgs Effective Field Theory framework by introducing new light degrees of freedom that can contribute to an invisible (or undetectable) Higgs decay width h → φφ, we show how differential coupling fits can disentangle effects from non-Standard Model couplings and an invisible decay width, as present in many new physics scenarios, such as Higgs-portal dark matter. Including the so-called off-shell measurement that has been advocated as a sensitive determination of the Higgs width in the κ framework, we show explicitly that this method does not provide complementary sensitivity for scale-separated new physics Λ >> m{sub h} >> m{sub φ}, which is favoured in beyond the Standard Model scenarios that relate astrophysics and collider phenomenology in the light of non-observation of new physics during run 1 of the LHC. (orig.)

Early Universe Higgs dynamics in the presence of the Higgs-inflaton and non-minimal Higgs-gravity couplings

Energy Technology Data Exchange (ETDEWEB)

Ema, Yohei [Department of Physics, Faculty of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Karčiauskas, Mindaugas [University of Jyväskylä, Department of Physics, P.O. Box 35 (YFL), FI-40014, Jyväskylä (Finland); Lebedev, Oleg; Zatta, Marco, E-mail: ema@hep-th.phys.s.u-tokyo.ac.jp, E-mail: mindaugas.m.karciauskas@jyu.fi, E-mail: oleg.lebedev@helsinki.fi, E-mail: marco.zatta@helsinki.fi [University of Helsinki and Helsinki Institute of Physics, P.O. Box 64, FI-00014, Helsinki (Finland)

2017-06-01

Apparent metastability of the electroweak vacuum poses a number of cosmological questions. These concern evolution of the Higgs field to the current vacuum, and its stability during and after inflation. Higgs-inflaton and non-minimal Higgs-gravity interactions can make a crucial impact on these considerations potentially solving the problems. In this work, we allow for these couplings to be present simultaneously and study their interplay. We find that different combinations of the Higgs-inflaton and non-minimal Higgs-gravity couplings induce effective Higgs mass during and after inflation. This crucially affects the Higgs stability considerations during preheating. In particular, a wide range of the couplings leading to stable solutions becomes allowed.

SM-like Higgs decay into two muons at 1.4 TeV CLIC

CERN Document Server

Milutinovic-Dumbelovic, Gordana

2016-06-02

The branching fraction measurement of the SM-like Higgs boson decay into two muons at 1.4 TeV CLIC will be described in this paper contributed to the LCWS13. The study is performed in the fully simulated ILD detector concept for CLIC, taking into consideration all the relevant physics and the beam-induced backgrounds, as well as the instrumentation of the very forward region to tag the high-energy electrons. Higgs couplings are known to be sensitive to BSM physics and we prove that BR times the Higgs production cross section can be measured with approximately 35.5% statistical accuracy in four years of the CLIC operation at 1.4 TeV centre-of-mass energy with unpolarised beams. The result is preliminary as the equivalent photon approximation is not considered in the cross-section calculations. This study complements the Higgs physics program foreseen at CLIC.

Phenomenology of the Higgs Effective Lagrangian via FeynRules

CERN Document Server

Alloul, Adam; Sanz, Verónica

2014-01-01

The Higgs discovery and the lack of any other hint for new physics favor a description of non-standard Higgs physics in terms of an effective field theory. We present an implementation of a general Higgs effective Lagrangian containing operators up to dimension six in the framework of FeynRules and provide details on the translation between the mass and interaction bases, in particular for three- and four-point interaction vertices involving Higgs and gauge bosons. We illustrate the strengths of this implementation by using the UFO interface of FeynRules capable to generate model files that can be understood by the MadGraph 5 event generator and that have the specificity to contain all interaction vertices, without any restriction on the number of external legs or on the complexity of the Lorentz structures. We then investigate several new physics effects in total rates and differential distributions for different Higgs production modes, including gluon fusion, associated production with a gauge boson and di-...

Fundamental Composite (Goldstone) Higgs Dynamics

DEFF Research Database (Denmark)

Cacciapaglia, G.; Sannino, Francesco

2014-01-01

We provide a unified description, both at the effective and fundamental Lagrangian level, of models of composite Higgs dynamics where the Higgs itself can emerge, depending on the way the electroweak symmetry is embedded, either as a pseudo-Goldstone boson or as a massive excitation of the conden...... searches of new physics at the Large Hadron Collider....

Higgs mass in the gauge-Higgs unification

International Nuclear Information System (INIS)

Haba, Naoyuki; Takenaga, Kazunori; Yamashita, Toshifumi

2005-01-01

The gauge-Higgs unification theory identifies the zero mode of the extra-dimensional component of the gauge field as the usual Higgs doublet. Since this degree of freedom is the Wilson line phase, the Higgs does not have the mass term nor quartic coupling at the tree level. Through quantum corrections, the Higgs can take a vacuum expectation value, and its mass is induced. The radiatively induced mass tends to be small, although it can be lifted to O(100) GeV by introducing the O(10) numbers of bulk fields. Perturbation theory becomes unreliable when a large number of bulk fields are introduced. We reanalyze the Higgs mass based on useful expansion formulae for the effective potential and find that even a small number of bulk field can have the suitable heavy Higgs mass. We show that a small (large) number of bulk fields are enough (needed) when the SUSY breaking mass is large (small). We also study the case of introducing the soft SUSY breaking scalar masses in addition to the Scherk-Schwarz SUSY breaking and obtain the heavy Higgs mass due to the effect of the scalar mass

The theoretical physics ecosystem behind the discovery of the Higgs boson

International Nuclear Information System (INIS)

Wells, James D.; Michigan Univ., Ann Arbor, MI

2016-09-01

The discovery of the Higgs boson in 2012 was one of the most significant developments of science in the last half century. A simplified history has Peter Higgs positing it in the mid-1960s followed by a long wait while experimentalists progressively turned up collider energies until it appeared several decades later. However, in order for both the hypothesis and the experimental discovery to occur, a vast and complex theory ecosystem had to thrive in the years before Higgs's hypothesis and in the years that followed, building up to its discovery. It is further claimed that the Higgs boson hypothesis was an immoderate speculation, and therefore faith in theory argumentation and speculation was mandatory for the discovery program to proceed and reach its fulfillment. The Higgs boson could not have been discovered experimentally by accident.

The theoretical physics ecosystem behind the discovery of the Higgs boson

Energy Technology Data Exchange (ETDEWEB)

Wells, James D. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Michigan Univ., Ann Arbor, MI (United States). Michigan Center for Theoretical Physics

2016-09-15

The discovery of the Higgs boson in 2012 was one of the most significant developments of science in the last half century. A simplified history has Peter Higgs positing it in the mid-1960s followed by a long wait while experimentalists progressively turned up collider energies until it appeared several decades later. However, in order for both the hypothesis and the experimental discovery to occur, a vast and complex theory ecosystem had to thrive in the years before Higgs's hypothesis and in the years that followed, building up to its discovery. It is further claimed that the Higgs boson hypothesis was an immoderate speculation, and therefore faith in theory argumentation and speculation was mandatory for the discovery program to proceed and reach its fulfillment. The Higgs boson could not have been discovered experimentally by accident.

Finding the Higgs boson: A status report

International Nuclear Information System (INIS)

Dawson, S.

1995-01-01

The search for the Higgs boson of the minimal Standard Model has been a major focus of experimental high energy physics for some years now. Here, the authors review the current experimental limits and discuss the prospects for finding the Higgs boson at future accelerators, such as LEPII and the LHC. They consider only the Standard Model Higgs boson. Since a null result which definitively excluded a Higgs boson below some mass scale would be extremely important, they emphasize the case where the Higgs boson is much heavier than the relevant collider energy (or where there is no Higgs boson at all). Many of the results given here are a summary of those obtained by the DPF Committee on Long Term Planning

Trilinear Higgs couplings in the two Higgs doublet model with CP violation

International Nuclear Information System (INIS)

Osland, Per; Pandita, P. N.; Selbuz, Levent

2008-01-01

We carry out a detailed analysis of the general two Higgs doublet model with CP violation. We describe two different parametrizations of this model, and then study the Higgs boson masses and the trilinear Higgs couplings for these two parametrizations. Within a rather general model, we find that the trilinear Higgs couplings have a significant dependence on the details of the model, even when the lightest Higgs boson mass is taken to be a fixed parameter. We include radiative corrections in the one-loop effective potential approximation in our analysis of the Higgs boson masses and the Higgs trilinear couplings. The one-loop corrections to the trilinear couplings of the two Higgs doublet model also depend significantly on the details of the model, and can be rather large. We study quantitatively the trilinear Higgs couplings, and show that these couplings are typically several times larger than the corresponding standard model trilinear Higgs coupling in some regions of the parameter space. We also briefly discuss the decoupling limit of the two Higgs doublet model.

ELECTROWEAK PHYSICS AND PRECISION STUDIES

International Nuclear Information System (INIS)

MARCIANO, W.

2005-01-01

The utility of precision electroweak measurements for predicting the Standard Model Higgs mass via quantum loop effects is discussed. Current values of m W , sin 2 θ W (m Z ) # ovr MS# and m t imply a relatively light Higgs which is below the direct experimental bound but possibly consistent with Supersymmetry expectations. The existence of Supersymmetry is further suggested by a 2σ discrepancy between experiment and theory for the muon anomalous magnetic moment. Constraints from precision studies on other types of ''New Physics'' are also briefly described

Prospecting for new physics in the Higgs and flavor sectors

Energy Technology Data Exchange (ETDEWEB)

Bishara, Fady [Univ. of Cincinnati, OH (United States)

2015-05-01

We explore two directions in beyond the standard model physics: dark matter model building and probing new sources of CP violation. In dark matter model building, we consider two scenarios where the stability of dark matter derives from the flavor symmetries of the standard model. The first model contains a flavor singlet dark matter candidate whose couplings to the visible sector are proportional to the flavor breaking parameters. This leads to a metastable dark matter with TeV scale mediators. In the second model, we consider a fully gauged SU(3)³ flavor model with a flavor triplet dark matter. Consequently, the dark matter multiplet is charged while the standard model fields are neutral under a remnant Z₃ which ensures dark matter stability. We show that a Dirac fermion dark matter with radiative splitting in the multiplet must have a mass in the range [0:5; 5] TeV in order to satisfy all experimental constraints. We then turn our attention to Higgs portal dark matter and investigate the possibility of obtaining bounds on the up, down, and strange quark Yukawa couplings. If Higgs portal dark matter is discovered, we find that direct detection rates are insensitive to vanishing light quark Yukawa couplings. We then review flavor models and give the expected enhancement or suppression of the Yukawa couplings in those models. Finally, in the last two chapters, we develop techniques for probing CP violation in the Higgs coupling to photons and in rare radiative decays of B mesons. While theoretically clean, we find that these methods are not practical with current and planned detectors. However, these techniques can be useful with a dedicated detector (e.g., a gaseous TPC). In the case of radiative B meson decay B⁰ → (K* → Kππ) γ, the techniques we develop also allow the extraction of the photon polarization fraction which is sensitive to new physics contributions since, in the standard model, the right(left) handed

Search for invisibly decaying Higgs boson at Large Hadron Collider

Indian Academy of Sciences (India)

In several scenarios of Beyond Standard Model physics, the invisible decay mode of the Higgs boson is an interesting possibility. The search strategy for an invisible Higgs boson at the Large Hadron Collider (LHC), using weak boson fusion process, has been studied in detail, by taking into account all possible ...

Invisible Higgs boson decay with B→Kνν constraint

International Nuclear Information System (INIS)

Kim, C. S.; Park, Seong Chan; Wang Kai; Zhu Guohuai

2010-01-01

If the Higgs boson were the only particle within the LHC accessible range, precision measurement of the Higgs's properties would play a unique role in studying electroweak symmetry breaking as well as possible new physics. We try to use low energy experiments such as rare B decay to constrain a challenging decay mode of Higgs, in which a Higgs decays to a pair of light (≅1∼2 GeV) SM singlet S and becomes invisible. By using the current experimental bound of rare decay B→Kνν and computing the contribution of B→KSS to (the) B→K+Ee, we obtain an upper bound on the Higgs coupling to such light singlet. It is interesting that the partial width of the invisible decay mode h→SS by taking the upper bound value of coupling is at a comparable level with h→WW/ZZ or WW ( * ) decay modes, making the Higgs identifiable but with a different predicted decay branching ratio from [the] standard model Higgs decay. It will then have an impact on precision measurement of the Higgs's properties. We also study the implication for cosmology from such a light singlet and propose a solution to the potential problem.

Qui attrapera le Higgs?

CERN Multimedia

Colas, Paul

2003-01-01

The Higgs boson was theoretically created about 40 years ago by a Scott Peter Higgs who wanted to explain why some particles get a mass. Since then the Higgs boson has taken consistency and has become an important point of the standard model theory. Its experimental discovery would be a milestone of modern physics. The search for the Higgs boson is an international challenge that takes place around 2 huge machines: the Tevatron near Chicago and the LHC (large hadron collider) that is being built in CERN. The Tevatron is in fact the upgrading of an old particle accelerator, it is a proton collider and its narrow range of energy is compensated by a low background noise. On the other hand the LHC will begin operating only in 2007 and its full power will be reached a few years later, the energy available to create particles will be then 7 times higher than for the Tevatron. Both machines have chance of succeeding by being the first to detect the Higgs boson. Time plays in favor of the Tevatron but in any case if ...

Top quark and Higgs physics in standard model extensions

Energy Technology Data Exchange (ETDEWEB)

Gonzalez, Patrick Jose

2012-05-25

In this thesis we have studied several extensions of the SM and their implications on the strength and structure of the tbW vertex, on the production and decays of pseudoscalar and heavy Higgs scalars at the LHC, and the effects that models with a fourth generation have on electroweak precision observables. Apart from the SM with a fourth generation of chiral fermions, the extensions we studied all feature an extended electroweak symmetry breaking (EWSB) sector. In the case of the type-II 2HDM and the MSSM, the extended EWSB sector consists of elementary Higgs fields. In the case of Topcolor assisted Technicolor (TC2), which is a model of dynamical EWSB, the scalar and pseudoscalar fields are composite. By scanning over the phenomenologically and theoretically allowed regions of the respective parameters spaces, we determined the largest possible cross sections σ(pp→φ→VV{sup '}) where VV{sup p}rime element of {W"+W"-, ZZγγ, Zγ} for both the heavy scalar and pseudoscalar states in the above models. We found that non-SUSY models with an extended Higgs sector and only three generations, namely the type-II 2HDM and the TC2, still allow for observable pseudoscalar cross sections σ(pp → A → VV') at the LHC. In particular for the final states W{sup +}W{sup -} and γγ. In the MSSM, the discovery of the pseudoscalar A through its decays into electroweak gauge bosons is very unlikely. However, scalar cross sections σ(pp→H→W{sup +}W{sup -}) can still be of observable size at the LHC in large parts of the MSSM parameter space. SM extensions with an extended EWSB sector and four chiral generations are strongly disfavoured; direct Higgs boson searches exclude large parts of the parameter space and it is challenging to bring such an extension into accordance with electroweak precision data. On the other hand, models with additional vector-like quarks and an extended Higgs sector are still viable. The SM with four chiral generations is (still) not

Exotic decays of the 125 GeV Higgs boson at future e+e- colliders

Science.gov (United States)

Liu, Zhen; Wang, Lian-Tao; Zhang, Hao

2017-06-01

The discovery of unexpected properties of the Higgs boson would offer an intriguing opportunity to shed light on some of the most profound puzzles in particle physics. Beyond Standard Model (BSM) decays of the Higgs boson could reveal new physics in a direct manner. Future electron-positron lepton colliders operating as Higgs factories, including CEPC, FCC-ee and ILC, with the advantages of a clean collider environment and large statistics, could greatly enhance sensitivity in searching for these BSM decays. In this work, we perform a general study of Higgs exotic decays at future e+e- lepton colliders, focusing on the Higgs decays with hadronic final states and/or missing energy, which are very challenging for the High-Luminosity program of the Large Hadron Collider (HL-LHC). We show that with simple selection cuts, (10-3-10-5) limits on the Higgs exotic decay branching fractions can be achieved using the leptonic decaying spectator Z boson in the associated production mode e+e-→ ZH. We further discuss the interplay between detector performance and Higgs exotic decays, and other possibilities of exotic decays. Our work is a first step in a comprehensive study of Higgs exotic decays at future lepton colliders, which is a key area of Higgs physics that deserves further investigation. Supported by Fermi Research Alliance, LLC (DE-AC02-07CH11359) with the U.S. Department of Energy, DOE (DE-SC0013642), IHEP(Y6515580U1), and IHEP Innovation (Y4545171Y2)

Limits from LEP Data on CP-Violating Nonminimal Higgs Sectors

International Nuclear Information System (INIS)

Gunion, J.F.; Grzadkowski, B.; Kalinowski, J.; Haber, H.E.; Kalinowski, J.

1997-01-01

We derive a sum rule which shows how to extend limits from LEP data on the masses of the lightest CP-even and CP-odd Higgs bosons of a CP-conserving two-Higgs doublet model to any two Higgs bosons of a general CP-violating two-Higgs-doublet model. We generalize the analysis to a Higgs sector consisting of an arbitrary number of Higgs doublets and singlets, giving explicit limits for the CP-conserving and CP-violating two-doublet plus one-singlet Higgs sectors. copyright 1997 The American Physical Society

How well do we need to measure Higgs boson couplings?

CERN Document Server

Gupta, Rick S.; Wells, James D.

2012-01-01

Most of the discussion regarding the Higgs boson couplings to Standard Model vector bosons and fermions is presented with respect to what present and future collider detectors will be able to measure. Here, we ask the more physics-based question of how well do we need to measure the Higgs boson couplings? We first present a reasonable definition of "need" and then investigate the answer in the context of various highly motivated new physics scenarios: supersymmetry, mixed-in hidden sector Higgs bosons, and a composite Higgs boson. We find the largest coupling deviations away from the SM Higgs couplings that are possible if no other state related to EWSB is directly accessible at the LHC. Depending on the physics scenario under consideration, we find targets that range from less than 1% to 10% for vector bosons, and from a few percent to tens of percent for couplings to fermions.

Dilaton vs Higgs: Nearly Conformal Physics

Science.gov (United States)

Kozlov, G. A.

2016-04-01

We consider the model in which the conformal symmetry can be broken spontaneously, and a light scalar dilaton could emerge in the low-energy spectrum. The contribution of the dark photon production relevant to two photons decays of a Higgs boson/dilaton is discussed.

Effective field theory analysis of Higgs naturalness

Energy Technology Data Exchange (ETDEWEB)

Bar-Shalom, Shaouly [Technion-Israel Inst. of Tech., Haifa (Israel); Soni, Amarjit [Brookhaven National Lab. (BNL), Upton, NY (United States); Wudka, Jose [Univ. of California, Riverside, CA (United States)

2015-07-20

Assuming the presence of physics beyond the Standard Model ( SM) with a characteristic scale M ~ O (10) TeV, we investigate the naturalness of the Higgs sector at scales below M using an effective field theory (EFT) approach. We obtain the leading 1 -loop EFT contributions to the Higgs mass with a Wilsonian-like hard cutoff, and determine t he constraints on the corresponding operator coefficients for these effects to alleviate the little hierarchy problem up to the scale of the effective action Λ < M , a condition we denote by “EFT-naturalness”. We also determine the types of physics that can lead to EFT-naturalness and show that these types of new physics are best probed in vector-boson and multiple-Higgs production. The current experimental constraints on these coefficients are also discussed.

Electroweak symmetry breaking: Higgs/whatever

International Nuclear Information System (INIS)

Chanowitz, M.S.

1990-01-01

In these two lectures the author discusses electroweak symmetry breaking from a general perspective, stressing properties that are model independent and follow just from the assumption that the electroweak interactions are described by a spontaneously broken gauge theory. This means he assumes the Higgs mechanism though not necessarily the existence of Higgs bosons. The first lecture presents the general framework of a spontaneously broken gauge theory: (1) the Higgs mechanism sui generis, with or without Higgs boson(s) and (2) the implications of symmetry and unitarity for the mass scale and interaction strength of the new physics that the Higgs mechanism requires. In addition he reviews a softer theoretical argument based on the naturalness problem which leads to a prejudice against Higgs bosons unless they are supersymmetric. This is a prejudice, not a theorem, and it could be overturned in the future by a clever new idea. In the second lecture he illustrates the general framework by reviewing some specific models: (1) the Weinberg-Salam model of the Higgs sector; (2) the minimal supersymmetric extension of the Weinberg-Salam model; and (3) technicolor as an example of the Higgs mechanism without Higgs bosons. He concludes the second lecture with a discussion of strong WW scattering that must occur if L SB lives above 1 TeV. In particular he describes some of the experimental signals and backgrounds at the SSC. 57 refs., 12 figs

HiggsBounds 2.0.0. Confronting neutral and charged Higgs sector predictions with exclusion bounds from LEP and the Tevatron

Energy Technology Data Exchange (ETDEWEB)

Bechtle, P.; Weiglein, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Brein, O. [Freiburg Univ. (Germany). Physikalisches Inst.; Heinemeyer, S. [Instituto de Fisica de Cantabria (CSIC-UC), Santander (Spain); Williams, K.E. [Bonn Univ. (Germany). Bethe Center for Theoretical Physics

2011-03-15

HiggsBounds 2.0.0 is a computer code which tests both neutral and charged Higgs sectors of arbitrary models against the current exclusion bounds from the Higgs searches at LEP and the Tevatron. As input, it requires a selection of model predictions, such as Higgs masses, branching ratios, effective couplings and total decay widths. HiggsBounds 2.0.0 then uses the expected and observed topological cross section limits from the Higgs searches to determine whether a given parameter scenario of a model is excluded at the 95% C.L. by those searches. Version 2.0.0 represents a significant extension of the code since its first release (1.0.0). It includes now 28/53 LEP/Tevatron Higgs search analyses, compared to the 11/22 in the first release, of which many of the ones from the Tevatron are replaced by updates. As a major extension, the code allows now the predictions for (singly) charged Higgs bosons to be confronted with LEP and Tevatron searches. Furthermore, the newly included analyses contain LEP searches for neutral Higgs bosons (H) decaying invisibly or into (non flavour tagged) hadrons as well as decay-mode independent searches for neutral Higgs bosons, LEP searches via the production modes {tau}{sup +}{tau}{sup -}H and b anti bH, and Tevatron searches via t anti tH. Also, all Tevatron results presented at the ICHEP'10 are included in version 2.0.0. As physics applications of HiggsBounds 2.0.0 we study the allowed Higgs mass range for model scenarios with invisible Higgs decays and we obtain exclusion results for the scalar sector of the Randall-Sundrum model using up-to-date LEP and Tevatron direct search results. (orig.)

Higgs, supersymmetry and dark matter after Run I of the LHC

CERN Document Server

Dumont, Beranger

2017-01-01

Two major problems call for an extension of the Standard Model (SM): the hierarchy problem in the Higgs sector and the dark matter in the Universe. The discovery of a Higgs boson with mass of about 125 GeV was clearly the most significant piece of news from CERN's Large Hadron Collider (LHC). In addition to representing the ultimate triumph of the SM, it shed new light on the hierarchy problem and opened up new ways of probing new physics. The various measurements performed at Run I of the LHC constrain the Higgs couplings to SM particles as well as invisible and undetected decays. In this thesis, the impact of the LHC Higgs results on various new physics scenarios is assessed, carefully taking into account uncertainties and correlations between them. Generic modifications of the Higgs coupling strengths, possibly arising from extended Higgs sectors or higher-dimensional operators, are considered. Furthermore, specific new physics models are tested. This includes, in particular, the phenomenological Minimal S...

Higgs boson search at ATLAS

International Nuclear Information System (INIS)

Hanninger, Guilherme Nunes

2012-01-01

Full text: The Standard Model of particle physics (SM) has been extremely successful describing the elementary particles and their interactions. It also features a theory describing the origin of particle masses: the 'Higgs mechanism', which postulates the existence of a new particle called the 'Higgs boson'. In 2011 and 2012, tantalising hints of the Higgs boson were reported by the experiments at the Large Hadron Collider (LHC). The results of the search for the Standard Model Higgs Boson with the ATLAS detector in proton-proton collisions at the LHC at 7 and 8 TeV center-of-mass energies are presented. A large number of the Higgs Boson decay channels, such as photon, tau, W and Z pairs, as well as for combined channels in the mass range from 110 GeV to 600 GeV are reviewed and discussed. The combined upper limits on the production cross section as a function of the Higgs Boson mass are derived. Practical methods to estimate the backgrounds using control samples in real data are discussed. Validation of some of the data driven background estimation methods using the early 7 TeV ATLAS data at the LHC is also presented. In addition, searches for Higgs Bosons in scenarios beyond the Standard Model (BSM) lead to improved constraints on the Higgs sector of BSM theories such as Supersymmetry. (author)

TOP AND HIGGS PHYSICS AT THE HADRON COLLIDERS

Energy Technology Data Exchange (ETDEWEB)

Jabeen, Shabnam

2013-10-20

This review summarizes the recent results for top quark and Higgs boson measurements from experiments at Tevatron, a proton–antiproton collider at a center-of-mass energy of √ s =1 . 96 TeV, and the Large Hadron Collider, a proton–proton collider at a center- of-mass energy of √ s = 7 TeV. These results include the discovery of a Higgs-like boson and measurement of its various properties, and measurements in the top quark sector, e.g. top quark mass, spin, charge asymmetry and production of single top quark.

Machine Learning wins the Higgs Challenge

CERN Multimedia

Abha Eli Phoboo

2014-01-01

The winner of the four-month-long Higgs Machine Learning Challenge, launched on 12 May, is Gábor Melis from Hungary, followed closely by Tim Salimans from the Netherlands and Pierre Courtiol from France. The challenge explored the potential of advanced machine learning methods to improve the significance of the Higgs discovery.   Winners of the Higgs Machine Learning Challenge: Gábor Melis and Tim Salimans (top row), Tianqi Chen and Tong He (bottom row). Participants in the Higgs Machine Learning Challenge were tasked with developing an algorithm to improve the detection of Higgs boson signal events decaying into two tau particles in a sample of simulated ATLAS data* that contains few signal and a majority of non-Higgs boson “background” events. No knowledge of particle physics was required for the challenge but skills in machine learning - the training of computers to recognise patterns in data – were essential. The Challenge, hosted by Ka...

PRECISION ELECTROWEAK MEASUREMENTS AND THE HIGGS MASS

International Nuclear Information System (INIS)

MARCIANO, W.J.

2004-01-01

The utility of precision electroweak measurements for predicting the Standard Model Higgs mass via quantum loop effects is discussed. Current constraints from m w and sin 2 θ w (m z ) ovr MS imply a relatively light Higgs ∼< 154 GeV which is consistent with Supersymmetry expectations. The existence of Supersymmetry is further suggested by a discrepancy between experiment and theory for the muon anomalous magnetic moment. Constraints from precision studies on other types of ''New Physics'' are also briefly described

ISR effects for resonant Higgs production at future lepton colliders

Directory of Open Access Journals (Sweden)

Mario Greco

2016-12-01

Full Text Available We study the effects of the initial state radiation on the s-channel Higgs boson resonant production at μ+μ− and e+e− colliders by convoluting with the beam energy spread profile of the collider and the Breit–Wigner resonance profile of the signal. We assess their impact on both the Higgs signal and SM backgrounds for the leading decay channels h→bb¯, WW⁎. Our study improves the existing analyses of the proposed future resonant Higgs factories and provides further guidance for the accelerator designs with respect to the physical goals.

Can the 125 GeV Higgs be the Little Higgs?

Energy Technology Data Exchange (ETDEWEB)

Reuter, J.; Tonini, M

2012-12-15

After the discovery of the Higgs-like boson by the LHC 2012 it is the most important task to check whether this new particle is the Standard Model Higgs boson or something else. In this paper, we study whether the 125 GeV boson could be the pseudo- Goldstone boson of Little Higgs models. We derive limits on the parameter space of several Little Higgs models (simple group and product group models, with and without T-parity), both from the experimental data from ATLAS and CMS about the different Higgs discovery channel and the electroweak precision observables. We perform a fit of several Little Higgs models to all electroweak parameters from measurements of SLC, LEP, Tevatron, and LHC. For the Higgs searches, we include all available data from the summer conferences 2012 as well as the update from December 2012.

Distinguishing a SM-like MSSM Higgs boson from SM Higgs boson ...

Indian Academy of Sciences (India)

We explore the possibility of distinguishing the SM-like MSSM Higgs boson from the SM Higgs boson via Higgs boson pair production at future muon collider. We study the behavior of the production cross-section in SM and MSSM with Higgs boson mass for various MSSM parameters tan and A. We observe that at fixed ...

CP Violation in Heavy MSSM Higgs Scenarios

CERN Document Server

Carena, M; Lee, J S; Pilaftsis, A; Wagner, C E M

2016-01-01

We introduce and explore new heavy Higgs scenarios in the Minimal Supersymmetric Standard Model (MSSM) with explicit CP violation, which have important phenomenological implications that may be testable at the LHC. For soft supersymmetry-breaking scales M_S above a few TeV and a charged Higgs boson mass M_H+ above a few hundred GeV, new physics effects including those from explicit CP violation decouple from the light Higgs boson sector. However, such effects can significantly alter the phenomenology of the heavy Higgs bosons while still being consistent with constraints from low-energy observables, for instance electric dipole moments. To consider scenarios with a charged Higgs boson much heavier than the Standard Model (SM) particles but much lighter than the supersymmetric particles, we revisit previous calculations of the MSSM Higgs sector. We compute the Higgs boson masses in the presence of CP violating phases, implementing improved matching and renormalization group (RG) effects, as well as two-loop RG...

Search for Higgs boson in beyond standard model scenarios

Indian Academy of Sciences (India)

The principal physics motivation of the LHC experiments is to search for the Higgs boson and to probe the physics of TeV energy scale. Potential of discovery for Higgs bosons in various scenarios beyond standard model have been estimated for both CMS and ATLAS experiments through detailed detector simulations.

Putting a Stop to di-Higgs Modifications

CERN Document Server

Batell, Brian; Stolarski, Daniel; Verhaaren, Christopher B

2015-01-01

Pair production of Higgs bosons at hadron colliders is an enticing channel to search for new physics. New colored particles that couple strongly to the Higgs, such as those most often called upon to address the hierarchy problem, provide well motivated examples in which large enhancements of the di-Higgs rate are possible, at least in principle. However, in such scenarios the di-Higgs production rate is tightly correlated with the single Higgs production rate and, since the latter is observed to be SM-like, one generally expects that only modest enhancements in di-Higgs production are allowed by the LHC Run 1 data. We examine the contribution of top squarks (stops) in a simplified supersymmetry model to di-Higgs production and find that this general expectation is indeed borne out. In particular, the allowed deviations are typically small, but there are tuned regions of parameter space where expectations based on EFT arguments break down in which order 100% enhancements to the di-Higgs production rate are pos...

BSM Higgs physics at the LHC in the forward proton mode

International Nuclear Information System (INIS)

Heinemeyer, S.; Khoze, V.A.; Tasevsky, M.; Weiglein, G.

2010-09-01

We review the prospects for Central Exclusive Diffractive (CED) production of Higgs bosons in the SM with a fourth generation of fermions at the LHC using forward proton detectors installed at 220 m and 420 m distance around ATLAS and / or CMS. We discuss the determination of Higgs spin-parity and coupling structures at the LHC and show that the forward proton mode would provide a critical information on the CP properties of the Higgs bosons. (orig.)

Towards a unified picture for gauge and Higgs fields

International Nuclear Information System (INIS)

Mecklenburg, W.

1981-01-01

A scheme for a geometrical unification of gauge and Higgs fields, previously given for SU 2 , is generalized to include arbitrary semisimple gauge groups. Gauge and physical Higgs fields appear as different components of the same tensor in a high dimensional manifold, the higher dimensions being comprised by the group coordinates. Their respective inhomogeneous transformation behaviour is derived from the same principle. The number of Higgs fields is restricted. The form of the Higgs potential is fixed and the mass of the Higgs particle is predicted in terms of the vector boson mass. (author)

Top quark and Higgs boson masses from wormhole physics

International Nuclear Information System (INIS)

Harris, B.A.; Joshi, G.C.

1994-01-01

We bring together quantum field theory on S 4 with the Coleman wormhole hypothesis, which imposes constraints on terms in the gravitational Lagrangian. In particular, we investigate the effect of matter fields on the trace anomaly, which is related to the (curvature) 2 terms, by the use of the renormalization group equations. We consider a toy model of a nonconformally coupled Higgs boson to a single ''top'' quark. By numerically solving the renormalization group equations for the couplings of the model, we can find preferred values of the particle masses for various values of the bare nonconformal coupling. By making the ad hoc assumption that the tree-level, Higgs boson treace anomaly vanishes on shell, a unique prediction can be made within this model for the masses of both the Higgs boson and the top quark

Number theory meets Higgs physics

CERN Multimedia

CERN. Geneva

2014-01-01

Inspired by results from modern number theory and algebraic geometry, a lot of progress has recently been made regarding the computation of multi-loop integrals and scattering amplitudes. I will discuss various new approaches to the computation of loop integrals, and illustrate them on the first computation of a quantity at N3LO in perturbative QCD, the soft-virtual part of the inclusive Higgs-boson cross section in gluon fusion at N3LO.

Higgs effective field theories. Systematics and applications

Energy Technology Data Exchange (ETDEWEB)

Krause, Claudius G.

2016-07-28

Researchers of the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) announced on July 4th, 2012, the observation of a new particle. The properties of the particle agree, within the relatively large experimental uncertainties, with the properties of the long-sought Higgs boson. Particle physicists around the globe are now wondering, ''Is it the Standard Model Higgs that we observe; or is it another particle with similar properties?'' We employ effective field theories (EFTs) for a general, model-independent description of the particle. We use a few, minimal assumptions - Standard Model (SM) particle content and a separation of scales to the new physics - which are supported by current experimental results. By construction, effective field theories describe a physical system only at a certain energy scale, in our case at the electroweak-scale v. Effects of new physics from a higher energy-scale, Λ, are described by modified interactions of the light particles. In this thesis, ''Higgs Effective Field Theories - Systematics and Applications'', we discuss effective field theories for the Higgs particle, which is not necessarily the Higgs of the Standard Model. In particular, we focus on a systematic and consistent expansion of the EFT. The systematics depends on the dynamics of the new physics. We distinguish two different consistent expansions. EFTs that describe decoupling new-physics effects and EFTs that describe non-decoupling new-physics effects. We briefly discuss the first case, the SM-EFT. The focus of this thesis, however, is on the non-decoupling EFTs. We argue that the loop expansion is the consistent expansion in the second case. We introduce the concept of chiral dimensions, equivalent to the loop expansion. Using the chiral dimensions, we expand the electroweak chiral Lagrangian up to next-to-leading order, O(f{sup 2}/Λ{sup 2})=O(1/16π{sup 2}). Further, we discuss how different

Superheavy dark matter through Higgs portal operators

Science.gov (United States)

Kolb, Edward W.; Long, Andrew J.

2017-11-01

The WIMPzilla hypothesis is that the dark matter is a super-weakly-interacting and superheavy particle. Conventionally, the WIMPzilla abundance is set by gravitational particle production during or at the end of inflation. In this study we allow the WIMPzilla to interact directly with Standard Model fields through the Higgs portal, and we calculate the thermal production (freeze-in) of WIMPzilla dark matter from the annihilation of Higgs boson pairs in the plasma. The two particle-physics model parameters are the WIMPzilla mass and the Higgs-WIMPzilla coupling. The two cosmological parameters are the reheating temperature and the expansion rate of the universe at the end of inflation. We delineate the regions of parameter space where either gravitational or thermal production is dominant, and within those regions we identify the parameters that predict the observed dark matter relic abundance. Allowing for thermal production opens up the parameter space, even for Planck-suppressed Higgs-WIMPzilla interactions.

Role of the CMS electromagnetic calorimeter in the measurement of the Higgs boson properties and search for new physics

Science.gov (United States)

Ferri, F.; CMS Collaboration

2016-04-01

The precise determination of the mass, the width and the couplings of the particle discovered in 2012 with a mass around 125 GeV is of capital importance to clarify the nature of such a particle, in particular to establish precisely if it is a Standard Model Higgs boson. In several new physics scenarios, in fact, the Higgs boson may behave differently with respect to the Standard Model one, or may not be unique, i.e. there can be more than one Higgs boson. In order to achieve the precision needed to discriminate between different models, the energy resolution, the scale uncertainty and the position resolution for electrons and photons are required to be as good as possible. The CMS scintillating lead-tungstate electromagnetic calorimeter (ECAL) was built as a precise tool with an exceptional energy resolution and a very good position resolution that improved over the years with the knowledge of the detector. Moreover, thanks to the fact that most of the lead-tungstate scintillation light is emitted in about 25 ns, the ECAL can be used to accurately determine the time of flight of photons. We present the current performance of the CMS ECAL, with a special emphasis on the impact on the measurement of the properties of the Higgs boson and on searches for new physics.

Standard Model–axion–seesaw–Higgs portal inflation. Five problems of particle physics and cosmology solved in one stroke

Energy Technology Data Exchange (ETDEWEB)

Ballesteros, Guillermo [Institut de Physique Théorique, Université Paris Saclay, CEA, CNRS, 91191 Gif-sur-Yvette (France); Redondo, Javier [Departamento de Física Teórica, Universidad de Zaragoza, Pedro Cerbuna 12, E-50009, Zaragoza (Spain); Ringwald, Andreas [DESY, Notkestr. 85, 22607 Hamburg (Germany); Tamarit, Carlos, E-mail: guillermo.ballesteros@cea.fr, E-mail: jredondo@unizar.es, E-mail: andreas.ringwald@desy.de, E-mail: carlos.tamarit@durham.ac.uk [Institute for Particle Physics Phenomenology, Durham University, South Road, DH1 3LE (United Kingdom)

2017-08-01

We present a minimal extension of the Standard Model (SM) providing a consistent picture of particle physics from the electroweak scale to the Planck scale and of cosmology from inflation until today. Three right-handed neutrinos N {sub i} , a new color triplet Q and a complex SM-singlet scalar σ, whose vacuum expectation value v {sub σ} ∼ 10{sup 11} GeV breaks lepton number and a Peccei-Quinn symmetry simultaneously, are added to the SM. At low energies, the model reduces to the SM, augmented by seesaw generated neutrino masses and mixing, plus the axion. The latter solves the strong CP problem and accounts for the cold dark matter in the Universe. The inflaton is comprised by a mixture of σ and the SM Higgs, and reheating of the Universe after inflation proceeds via the Higgs portal. Baryogenesis occurs via thermal leptogenesis. Thus, five fundamental problems of particle physics and cosmology are solved at one stroke in this unified Standard Model—axion—seesaw—Higgs portal inflation (SMASH) model. It can be probed decisively by upcoming cosmic microwave background and axion dark matter experiments.

Standard Model-Axion-Seesaw-Higgs portal inflation. Five problems of particle physics and cosmology solved in one stroke

International Nuclear Information System (INIS)

Ballesteros, Guillermo; Ringwald, Andreas; Tamarit, Carlos

2016-10-01

We present a minimal extension of the Standard Model (SM) providing a consistent picture of particle physics from the electroweak scale to the Planck scale and of cosmology from inflation until today. Three right-handed neutrinos N_i, a new color triplet Q and a complex SM-singlet scalar σ, whose vacuum expectation value υ_σ∝10"1"1 GeV breaks lepton number and a Peccei-Quinn symmetry simultaneously, are added to the SM. At low energies, the model reduces to the SM, augmented by seesaw generated neutrino masses and mixing, plus the axion. The latter solves the strong CP problem and accounts for the cold dark matter in the Universe. The inflaton is comprised by a mixture of σ and the SM Higgs and reheating of the Universe after inflation proceeds via the Higgs portal. Baryogenesis occurs via thermal leptogenesis. Thus, five fundamental problems of particle physics and cosmology are solved at one stroke in this unified Standard Model-Axion-Seesaw-Higgs portal inflation (SMASH) model. It can be probed decisively by upcoming cosmic microwave background and axion dark matter experiments.

Higgs discovered at Open Days

CERN Multimedia

2008-01-01

Like his eponymous particle, Peter Higgs can be elusive. However, for the momentous occasion of the Open Days there was a chance, if you were lucky, to catch a glimpse of him. Peter Higgs marvels at the enormity of the ATLAS experiment. Taking a closer look at CMS.Visiting CERN for the first time in more than 20 years, Peter Higgs has become something of a celebrity in the world of particle physics. During his visit he showed genuine amazement at the sight of the LHC and its experiments. On seeing CMS he said, "It’s very impressive, very dramatic. I’d seen pictures of course, but they can’t compare." Surrounded for most of his stay by an entourage of physicists, the notoriously modest scientist laughs at the almost mythical quality his boson has taken on. For him though, it is just one of many aspects of physics that the CMS and ATLAS experiments can shine a light on. Besides finding ...

The Higgs-strahlung and double Higgs-strahlung production in the left-right twin Higgs model at the ILC

International Nuclear Information System (INIS)

Yao-Bei, Liu; Hong-Mei, Han; Xue-Lei, Wang

2008-01-01

The Higgs-strahlung process e + e - → ZH and the double Higgs-strahlung process e + e - → ZHH are very important for studying Higgs boson properties and the Higgs self-coupling in the high-energy e + e - collider (ILC). We calculate the contributions of the left-right twin Higgs (LRTH) model to these processes and find that, in the favorable parameter spaces, the LRTH model can generate significant corrections to the production cross-section of these processes. We expect that the possible signals of the LRTH model can be detected via these processes in the future ILC experiments. (authors)

Very boosted Higgs in gluon fusion

CERN Document Server

Grojean, Christophe; Schlaffer, Matthias; Weiler, Andreas

2014-01-01

The Higgs production and decay rates offer a new way to probe new physics beyond the Standard Model. While dynamics aiming at alleviating the hierarchy problem generically predict deviations in the Higgs rates, the current experimental analyses cannot resolve the long- and short-distance contributions to the gluon fusion process and thus cannot access directly the coupling between the Higgs and the top quark. We investigate the production of a boosted Higgs in association with a high-transverse momentum jet as an alternative to the $t\\bar{t}h$ channel to pin down this crucial coupling. Presented first in the context of an effective field theory, our analysis is then applied to models of partial compositeness at the TeV scale and of natural supersymmetry.

Very boosted Higgs in gluon fusion

Energy Technology Data Exchange (ETDEWEB)

Grojean, C. [Univ. Autonoma de Barcelona, Bellaterra (Spain). ICREA at IFAE; Salvioni, E. [California Univ., Davis, CA (United States). Dept. of Physics; European Organization for Nuclear Research (CERN), Geneva (Switzerland); Padova Univ. (Italy). Dipt. di Fisica e Astronomica; INFN, Sezione di Padova (Italy); Schlaffer, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Weiler, A. [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2013-12-15

The Higgs production and decay rates offer a new way to probe new physics beyond the Standard Model. While dynamics aiming at alleviating the hierarchy problem generically predict deviations in the Higgs rates, the current experimental analyses cannot resolve the long- and short-distance contributions to the gluon fusion process and thus cannot access directly the coupling between the Higgs and the top quark. We investigate the production of a boosted Higgs in association with a high-transverse momentum jet as an alternative to the t anti th channel to pin down this crucial coupling. Presented rst in the context of an effective field theory, our analysis is then applied to models of partial compositeness at the TeV scale and of natural supersymmetry.

Higgs mass bounds from a chirally invariant lattice Higgs-Yukawa model with overlap fermions

International Nuclear Information System (INIS)

Gerhold, Philipp; Kallarackal, Jim

2008-10-01

We study the parameter dependence of the Higgs mass in a chirally invariant lattice Higgs-Yukawa model emulating the same Higgs-fermion coupling structure as in the Higgs sector of the electroweak Standard Model. Eventually, the aim is to establish upper and lower Higgs mass bounds. Here we present our preliminary results on the lower Higgs mass bound at several selected values for the cutoff and give a brief outlook towards the upper Higgs mass bound. (orig.)

Higgs Boson and New Physics Searches in Events with Same-sign Lepton Pairs at the LHC

CERN Document Server

AUTHOR|(INSPIRE)INSPIRE-00346170

The physics of elementary particles is well described by the Standard Model of particle physics. This theory predicts with great accuracy the electroweak and strong interactions of elementary particles. The introduction of the Brout-Englert-Higgs mechanism in Standard Model has also given justification to the non-null mass of the elementary particles. This mechanism has been validated by the discovery of the Higgs boson and the measurement of its properties. Despite the enormous and broad success of the Standard Model, a few observations cannot be explained by this theory. For instance, neutrino oscillations would require the neutrinos to have non-null mass in contrast with the Standard Model prediction. Several solutions to this problem have been proposed, but none has been validated yet. Some of these theories have additional modes to produce lepton pairs with same electric charge (same-sign lepton pairs). This production is also expected to be enhanced in other theories beyond the Standard Model. The focus...

A theoretical limit on the Higgs mass

International Nuclear Information System (INIS)

Temiraliev, A.T.

2007-01-01

Full text: The standard model of particle physics, which describes masses through the Higgs mechanism, contains parameters - such as particle masses - whose origins are still unknown and which cannot be exactly predicted, but whose values are constrained through their interactions. In particular, the masses of the top quark and W boson constrain the mass of the long-hypothesized, but thus far not observed, Higgs boson. Several more or less precise arguments can set the upper limit for a standard model Higgs particle. All of them follows the line that the standard model breaks down of the Higgs mass is pushed too far upwards. The theoretical bounds will be reviewed. With gauge-top quark Yukawa coupling unification the standard model Higgs boson mass is estimated to be about 135 GeV. In the article will be consider an approximation of 4-fermion interactions. And as a result, the most likely Higgs mass is 150 GeV. The upper limit on the Higgs mass at the 90 % confidence level is about 250 GeV

On-shell neutral Higgs bosons in the NMSSM with complex parameters

Energy Technology Data Exchange (ETDEWEB)

Domingo, Florian [Universidad Autonoma de Madrid, Instituto de Fisica Teorica (UAM/CSIC), Cantoblanco, Madrid (Spain); Instituto de Fisica de Cantabria (CSIC-UC), Santander (Spain); Drechsel, Peter; Passehr, Sebastian [Deutsches Elektronensynchrotron DESY, Hamburg (Germany)

2017-08-15

The Next-to-Minimal Supersymmetric Standard model (NMSSM) appears as an interesting candidate for the interpretation of the Higgs measurement at the LHC and as a rich framework embedding physics beyond the Standard Model. We consider the renormalization of the Higgs sector of this model in its CP-violating version, and propose a renormalization scheme for the calculation of on-shell Higgs masses. Moreover, the connection between the physical states and the tree-level ones is no longer trivial at the radiative level: a proper description of the corresponding transition thus proves necessary in order to calculate Higgs production and decays at a consistent loop order. After discussing these formal aspects, we compare the results of our mass calculation to the output of existing tools. We also study the relevance of the on-shell transition matrix in the example of the h{sub i} → τ{sup +}τ{sup -} width. We find deviations between our full prescription and popular approximations that can exceed 10%. (orig.)

The discovery of the Higgs particle. Or how the universe got its mass. 3. ed.; Die Entdeckung des Higgs-Teilchens. Oder wie das Universum seine Masse bekam

Energy Technology Data Exchange (ETDEWEB)

Lesch, Harald (ed.) [Muenchen Univ. (Germany). Inst. fuer Astronomie und Astrophysik

2013-07-01

Higgs - that is a physicist, a field, a particle. 1964 only the idea of Peter Higgs and some other physicists existed: A theory for specialists of particle physics. Since the 1980th years then in the underground at Geneva the largest machine of mankind was built - consisting of a nearly 27 kilometers long ring tunnel and gigantic detectors. In this enormous facility, called LHC (Large Hadron Collider), particles were accelerated nearly to light velocity. In its collisions they should produce the predicted Higgs particle. Finally in 2012 the detection succeeded - the Higgs particle exists really. And also a Higgs field exists. It penetrates the whole cosmos and mediates to the particles the property of the rest mass. Nearly men have never came to the big bang. And Peter Higgs received 2013 with Francois Englert the Nobel prize of physics. Harald Lesch and his coworkers report from the expensive search for the Higgs particle, the theoretical conditions and consequences for the particle physics. They clarify what it's called ''God particle'' or fears about a black hole arising in the LHC experiment. An exciting narrative about the foundations of our universe and the fascination at the fringe of the recognizable reality.

Higgs instability and de Sitter radiation

Directory of Open Access Journals (Sweden)

Gaurav Goswami

2015-12-01

Full Text Available If the Standard Model (SM of elementary particle physics is assumed to hold good to arbitrarily high energies, then, for the best fit values of the parameters, the scalar potential of the Standard Model Higgs field turns negative at a high scale μinst. If the physics beyond the SM is such that it does not modify this feature of the Higgs potential and if the Hubble parameter during inflation (Hinf is such that Hinf≫μinst, then, quantum fluctuations of the SM Higgs during inflation make it extremely unlikely that after inflation it will be found in the metastable vacuum at the weak scale. In this work, we assume that (i during inflation, the SM Higgs is in Bunch–Davies vacuum state, and, (ii the question about the stability of the effective potential must be answered in the frame of the freely falling observer (just like in Minkowski spacetime, and then use the well-known fact that the freely falling observer finds Bunch–Davies vacuum to be in thermal state to show that the probability to end up in the electroweak vacuum after inflation is reasonably high.

Who will catch the Higgs boson?

International Nuclear Information System (INIS)

Colas, P.; Tuchming, B.

2004-01-01

The Higgs boson was theoretically created about 40 years ago by a Scott Peter Higgs who wanted to explain why some particles get a mass. Since then the Higgs boson has taken consistency and has become an important point of the standard model theory. Its experimental discovery would be a milestone of modern physics. The search for the Higgs boson is an international challenge that takes place around 2 huge machines: the Tevatron near Chicago and the LHC (large hadron collider) that is being built in CERN. The Tevatron is in fact the upgrading of an old particle accelerator, it is a proton collider and its narrow range of energy is compensated by a low background noise. On the other hand the LHC will begin operating only in 2007 and its full power will be reached a few years later, the energy available to create particles will be then 7 times higher than for the Tevatron. Both machines have chance of succeeding by being the first to detect the Higgs boson. Time plays in favor of the Tevatron but in any case if the Higgs boson exists it will be detected at LHC because this equipment covers completely the energy range in which the Higgs boson is suspected to exist. (A.C.)

Smashing physics. Inside the world's biggest experiment; Der Kosmos im Crashtest. So haben wir das Higgs gejagt

Energy Technology Data Exchange (ETDEWEB)

Butterworth, Jon [University College, London (United Kingdom). Fachbereich Physik und Astronomie

2015-11-01

The discovery of the Higgs boson made headlines around the world. Two scientists, Peter Higgs and Francois Englert, whose theories predicted its existence, shared a Nobel Prize. The discovery was the culmination of the largest experiment ever run, the ATLAS and CMS experiments at CERN's Large Hadron Collider. But what really is a Higgs boson and what does it do? How was it found? And how has its discovery changed our understanding of the fundamental laws of nature? And what did it feel like to be part of it? Jon Butterworth is one of the leading physicists at CERN and this book is the first popular inside account of the hunt for the Higgs. It is a story of incredible scientific collaboration, inspiring technological innovation and ground-breaking science. It is also the story of what happens when the world's most expensive experiment blows up, of neutrinos that may or may not travel faster than light, and the reality of life in an underground bunker in Switzerland. This book will also leave you with a working knowledge of the new physics and what the discovery of the Higgs particle means for how we define the laws of nature. It will take you to the cutting edge of modern scientific thinking.

Higgs for the masses

Energy Technology Data Exchange (ETDEWEB)

Anon.

1986-03-15

The unified theory of electromagnetism and the weak nuclear force, crowned with the discovery at CERN in 1983 of the W and Z bosons which carry the weak nuclear force, is one of the great triumphs of modern physics. But the picture is not yet complete. An essential but still elusive ingredient is the so-called 'Higgs boson' (after Edinburgh theorist Peter Higgs), responsible for the vital symmetry breaking in the theory. This gives the carriers of the weak force mass, while the photon, the carrier of electromagnetism, is massless.

Flavor with a light dynamical "Higgs particle"

CERN Document Server

Alonso, R.; Merlo, L.; Rigolin, S.; Yepes, J.

2013-01-01

The Higgs-fermion couplings are sensitive probes of possible new physics behind a stable light Higgs particle. It is then essential to identify the flavour pattern of those interactions. We consider the case in which a strong dynamics lies behind a light Higgs, and explore the implications within the Minimal Flavour Violation ansatz. The dominant effects on flavour-changing Higgs-fermion couplings stem in this context from operators with mass dimension <6, and we analyze all relevant chiral operators up to that order, including loop-corrections induced by 4-dimensional ones. Bounds on the operator coefficients are derived from a plethora of low-energy flavour transitions, providing a guideline on which flavour-changing Higgs interactions may be open to experimental scrutiny. In particular, the coefficient of a genuinely CP-odd operator is only softly constrained and therefore its impact is potentially interesting.

New results on Higgs boson physics from the ATLAS experiment

CERN Multimedia

CERN. Geneva

2018-01-01

The ATLAS Collaboration has recently released several results that shed more light on the nature of the Higgs boson particle and the BEH mechanism. A selection of these Higgs boson results, including some results based on up to 80 fb-1of integrated luminosity collected at a centre-of-mass energy of 13 TeV with the ATLAS experiment at the LHC, will be presented.

The Higgs boson. The greatest discovery of the century - And Higgs entered history. A window on hidden reality

International Nuclear Information System (INIS)

Khalatbari, Azar

2012-01-01

This article recalls the history and actors of scientific research in particle physics which leaded to the hypothesis and later the evidence of the existence of the Higgs boson. It evokes the main accelerators since 1931 (the Lawrence cyclotron, the Cockcroft Walton generator, the LEP electron-proton collider, the Tevatron), until the CERN Large Hadron Collider (LHC). Then, it discusses how the existence of the Higgs boson which confirms the physics standard model, creates new theoretical perspectives for the understanding of cosmos history, notably for the Universe missing mass, dark energy, and so on

CMS latest results on Higgs measurements

CERN Multimedia

CERN. Geneva

2014-01-01

Since the discovery of a Higgs boson by the CMS and ATLAS Collaborations in 2012, physicists at the LHC have been making intense efforts to measure this new particle’s properties. Last week, at the 37th International Conference on High Energy Physics, the CMS Collaboration has presented a broad set of results from new studies of the Higgs boson. They are based on the full Run 1 data from pp collisions at centre-of-mass energies of 7 and 8 TeV. The analyses include the final calibration and alignment constants and contains about 25 fb−1 of data. These new results will be summarized here.

Higgs inflation and the cosmological constant

Energy Technology Data Exchange (ETDEWEB)

Jegerlehner, Fred [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)

2014-02-15

The Higgs not only induces the masses of all SM particles, the Higgs, given its special mass value, is the natural candidate for the inflaton and in fact is ruling the evolution of the early universe, by providing the necessary dark energy which remains the dominant energy density. SM running couplings not only allow us to extrapolate SM physics up to the Planck scale, but equally important they are triggering the Higgs mechanism. This is possible by the fact that the bare mass term in the Higgs potential changes sign at about μ{sub 0}≅1.40 x 10{sup 16} GeV and in the symmetric phase is enhanced by quadratic terms in the Planck mass. Such a huge Higgs mass term is able to play a key role in triggering inflation in the early universe. In this article we extend our previous investigation by working out the details of a Higgs inflation scenario. We show how different terms contributing to the Higgs Lagrangian are affecting inflation. Given the SM and its extrapolation to scales μ>μ{sub 0} we find a calculable cosmological constant V(0) which is weakly scale dependent and actually remains large during inflation. This is different to the Higgs fluctuation field dependent ΔV(φ), which decays exponentially during inflation, and actually would not provide a sufficient amount of inflation. The fluctuation field has a different effective mass which shifts the bare Higgs transition point to a lower value μ'{sub 0} ≅7.7 x 10{sup 14} GeV. The vacuum energy V(0) being proportional to M{sub Pl}{sup 4} has a coefficient which vanishes near the Higgs transition point, such that the bare and the renormalized cosmological constant match at this point. The role of the Higgs in reheating and baryogenesis is emphasized.

Higgs boson production and decay in little Higgs models with T-parity

International Nuclear Information System (INIS)

Chen, C.-R.; Tobe, Kazuhiro; Yuan, C.-P.

2006-01-01

We study Higgs boson production and decay in a certain class of little Higgs models with T-parity in which some T-parity partners of the Standard Model (SM) fermions gain their masses through Yukawa-type couplings. We find that the Higgs boson production cross section of a 120 GeV Higgs boson at the CERN LHC via gg fusion process at one-loop level could be reduced by about 45%, 35% and 20%, as compared to its SM prediction, for a relatively low new particle mass scale f=600, 700 and 1000 GeV, respectively. On the other hand, the weak boson fusion cross section is close to the SM value. Furthermore, the Higgs boson decay branching ratio into di-photon mode can be enhanced by about 35% in small Higgs mass region in certain case, for the total decay width of Higgs boson in the little Higgs model is always smaller than that in the SM

Neutral Higgs bosons in the standard model and in the minimal ...

Indian Academy of Sciences (India)

assumed to be CP invariant. Finally, we discuss an alternative MSSM scenario including. CP violation in the Higgs sector. Keywords. Higgs bosons; standard model; minimal supersymmetric model; searches at LEP. 1. Introduction. One of the challenges in high-energy particle physics is the discovery of Higgs bosons.

NMSSM interpretations of the observed Higgs signal

International Nuclear Information System (INIS)

Domingo, Florian; Weiglein, Georg

2015-01-01

While the properties of the signal that was discovered in the Higgs searches at the LHC are consistent so far with the Higgs boson of the Standard Model (SM), it is crucial to investigate to what extent other interpretations that may correspond to very different underlying physics are compatible with the current results. We use the Next-to-Minimal Supersymmetric Standard Model (NMSSM) as a well-motivated theoretical framework with a sufficiently rich Higgs phenomenology to address this question, making use of the public tools HiggsBounds and HiggsSignals in order to take into account comprehensive experimental information on both the observed signal and on the existing limits from Higgs searches at LEP, the TeVatron and the LHC. We find that besides the decoupling limit resulting in a single light state with SM-like properties, several other configurations involving states lighter or quasi-degenerate with the one at about 125 GeV turn out to give a competitive fit to the Higgs data and other existing constraints. We discuss the phenomenology and possible future experimental tests of those scenarios, and compare the features of specific scenarios chosen as examples with those arising from a more global fit.

CMS presents new boundary of Higgs width

CERN Multimedia

Katarina Anthony

2014-01-01

At last year's Moriond conference, CERN physicists announced the retirement of the "Higgs-like" particle and the arrival of "boson, Higgs boson". Now, one year later, at the same session in the same conference, physicists are back with more exciting news about the famed particle. This time: the best constraint yet of the Higgs Boson “width”, a parameter that determines the particle’s lifetime.   Rencontres de Moriond 2014. As a key indicator for new physics, the Higgs “width” has long been on the LHC "to-do" list. Now less than two years post-discovery, the CMS experiment has gotten the closest yet to pinning it down, constraining the parameter to < 17 MeV with 95% confidence. This result is some two orders of magnitude better than previous limits: stronger evidence that this boson looks like the Standard Model Higgs boson. "It's been exciting to see how wel...

Does low-energy physics depend on the potential of a heavy Higgs-particle?

International Nuclear Information System (INIS)

Bij, J.J. van der.

1985-01-01

The two-loop corrections to vectorboson-propagators and vertices are calculated in the limit of large Higgs-mass for a model with one Higgs-doublet but arbitrary gauge-invariant potential. The corrections are finite even for a non-renormalizable potential. By a suitable choice of the φ 6 term in the potential the corrections due to the Higgs self-coupling are cancelled. (Auth.)

Perturbed Lepton-Specific Two-Higgs-Doublet Model Facing Experimental Hints for Physics beyond the Standard Model.

Science.gov (United States)

Crivellin, Andreas; Heeck, Julian; Stoffer, Peter

2016-02-26

BABAR, Belle, and LHCb Collaborations report evidence for new physics in B→Dτν and B→D^{*}τν of approximately 3.8σ. There is also the long lasting discrepancy of about 3σ in the anomalous magnetic moment of the muon, and the branching ratio for τ→μνν is 1.8σ (2.4σ) above the standard model expectation using the HFAG (PDG) values. Furthermore, CMS Collaboration finds hints for a nonzero decay rate of h→μτ. Interestingly, all these observations can be explained by introducing new scalars. In this Letter we consider these processes within a lepton-specific two-Higgs doublet model (i.e., of type X) with additional nonstandard Yukawa couplings. It is found that one can accommodate τ→μνν with modified Higgs-τ couplings. The anomalous magnetic moment of the muon can be explained if the additional neutral CP-even Higgs boson H is light (below 100 GeV). Also R(D) and R(D^{*}) can be easily explained by additional t-c-Higgs couplings. Combining these t-c couplings with a light H the decay rate for t→Hc can be in a testable range for the LHC. Effects in h→μτ are also possible, but in this case a simultaneous explanation of the anomalous magnetic moment of the muon is difficult due to the unavoidable τ→μγ decay.

Generalized Higgs inflation

Energy Technology Data Exchange (ETDEWEB)

Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kobayashi, Tsutomu [Kyoto Univ. (Japan). Hakubi Center; Kyoto Univ. (Japan). Dept. of Physics; Takahashi, Tomo [Saga Univ. (Japan). Dept. of Physics; Yamaguchi, Masahide [Tokyo Institute of Technology (Japan). Dept. of Physics; Yokoyama, Jun' ichi [Tokyo Univ. (JP). Research Center for the Early Universe (RESCEU); Tokyo Univ., Chiba (JP). Inst. for the Physics and Mathematics of the Universe (IPMU)

2012-03-15

We study Higgs inflation in the context of generalized G-inflation, i.e., the most general single-field inflation model with second-order field equations. The four variants of Higgs inflation proposed so far in the literature can be accommodated at one time in our framework. We also propose yet another class of Higgs inflation, the running Einstein inflation model, that can naturally arise from the generalized G-inflation framework. As a result, five Higgs inflation models in all should be discussed on an equal footing. Concise formulas for primordial fluctuations in these generalized Higgs inflation models are provided, which will be helpful to determine which model is favored from the future experiments and observations such as the Large Hadron Collider and the Planck satellite.

Approximate N3LO Higgs-boson production cross section using physical-kernel constraints

International Nuclear Information System (INIS)

Florian, D. de; Moch, S.; Hamburg Univ.; Vogt, A.

2014-08-01

The single-logarithmic enhancement of the physical kernel for Higgs production by gluon-gluon fusion in the heavy top-quark limit is employed to derive the leading so far unknown contributions, ln 5,4,3 (1-z), to the N 3 LO coefficient function in the threshold expansion. Also using knowledge from Higgs-exchange DIS to estimate the remaining terms not vanishing for z=m 2 H /s→1, these results are combined with the recently completed soft+virtual contributions to provide an uncertainty band for the complete N 3 LO correction. For the 2008 MSTW parton distributions these N 3 LO contributions increase the cross section at 14 TeV by (10±2)% and (3±2.5)% for the standard choices μ R =m H and μ R =m H /2 of the renormalization scale. The remaining uncertainty arising from the hard-scattering cross sections can be quantified as no more than 5%, which is smaller than that due to the strong coupling and the parton distributions.

Induced gravity with Higgs potential. Elementary interactions and quantum processes

International Nuclear Information System (INIS)

Bezares Roder, Nils Manuel

2010-01-01

This work is intended to first serve as introduction in fundamental subjects of physics in order to be then able to review the mechanism of symmetry breakdown and its essential character in physics. It introduces the concept of scalar-tensor theories of gravity based on Bergmann-Wagoner models with a Higgs potential. The main physical context aimed is the problem of Dark Matter and Dark Energy. On the one hand, there is gravitation. Within this context, we have Dark Matter as an especially relevant concept. This work entails the following main contributions: - General features of Einstein's theory are introduced together with generalities of the different elementary interactions of physics from which the concepts of dark sectors and Higgs Mechanism are derived. - The concept of symmetry breaking and especially the Higgs Mechanism of mass generation are discussed in their relevance for the most different subjects of physics, especially in relation to the Standard Model of elementary particle physics with elementary Higgs fields. - Scalar-Tensor Theories are introduced in order to build in them the process of Higgs Mechanism. This is then fulfilled with a theory of induced gravity with a Higgs potential which seems renormalizable according to deWitt's power counting criterion, and with mass-generating Higgs fields which only couple gravitationally as well as with Higgs fields which act analogously to cosmon fields. - Further, the energy density of the gravitational field is derived for the specific model of induced gravity from an analogy to electrodynamics. It is shown that a nonvanishing value of pressure related to the scalar field is necessary in order to reproduce standard linear solar-relativistic dynamics. Within astrophysical considerations for flat rotation curves of galaxies, a possible dark-matter behavior is concluded within spherical symmetry. The scalar field and the dark-matter profile of total energy density are derived. An analogous relation between

Induced gravity with Higgs potential. Elementary interactions and quantum processes

Energy Technology Data Exchange (ETDEWEB)

Bezares Roder, Nils Manuel

2010-07-01

This work is intended to first serve as introduction in fundamental subjects of physics in order to be then able to review the mechanism of symmetry breakdown and its essential character in physics. It introduces the concept of scalar-tensor theories of gravity based on Bergmann-Wagoner models with a Higgs potential. The main physical context aimed is the problem of Dark Matter and Dark Energy. On the one hand, there is gravitation. Within this context, we have Dark Matter as an especially relevant concept. This work entails the following main contributions: - General features of Einstein's theory are introduced together with generalities of the different elementary interactions of physics from which the concepts of dark sectors and Higgs Mechanism are derived. - The concept of symmetry breaking and especially the Higgs Mechanism of mass generation are discussed in their relevance for the most different subjects of physics, especially in relation to the Standard Model of elementary particle physics with elementary Higgs fields. - Scalar-Tensor Theories are introduced in order to build in them the process of Higgs Mechanism. This is then fulfilled with a theory of induced gravity with a Higgs potential which seems renormalizable according to deWitt's power counting criterion, and with mass-generating Higgs fields which only couple gravitationally as well as with Higgs fields which act analogously to cosmon fields. - Further, the energy density of the gravitational field is derived for the specific model of induced gravity from an analogy to electrodynamics. It is shown that a nonvanishing value of pressure related to the scalar field is necessary in order to reproduce standard linear solar-relativistic dynamics. Within astrophysical considerations for flat rotation curves of galaxies, a possible dark-matter behavior is concluded within spherical symmetry. The scalar field and the dark-matter profile of total energy density are derived. An analogous

Can we distinguish an MSSM Higgs from a SM Higgs at a linear collider?

International Nuclear Information System (INIS)

Logan, Heather E.

2001-01-01

We study the prospects for distinguishing the CP-even Higgs boson of the minimal supersymmetric extension of the Standard Model (MSSM) from the Standard Model (SM) Higgs boson by measuring its branching ratios at an e + e - linear collider. The regions of the M A -tan β plane in which an MSSM Higgs boson can be distinguished from the SM Higgs boson depend strongly upon the supersymmetric parameters that enter the radiative corrections to the Higgs mass matrix and the Higgs couplings to fermions. In some regions of parameter space it is possible to extract the supersymmetric correction to the relation between the b quark mass and its Yukawa coupling from Higgs branching ratio measurements

BSM Higgs physics in the exclusive forward proton mode at the LHC

International Nuclear Information System (INIS)

Heinemeyer, S.; Khoze, V.A.; Tasevsky, M.; Weiglein, G.

2010-12-01

We investigate the prospects for Central Exclusive Diffractive (CED) production of BSM Higgs bosons at the LHC using forward proton detectors installed at 220 m and 420 m distance around ATLAS and/or CMS. We update a previous analysis for the MSSM taking into account improvements in the theoretical calculations and the most recent exclusion bounds from the Tevatron. We extend the MSSM analysis to new benchmark scenarios that are in agreement with the cold dark matter relic abundance and other precision measurements. We analyse the exclusive production of Higgs bosons in a model with a fourth generation of fermions. Finally, we comment on the determination of Higgs spin-parity and coupling structures at the LHC and show that the forward proton mode could provide crucial information on the CP properties of the Higgs bosons. (orig.)

BSM Higgs physics in the exclusive forward proton mode at the LHC

Energy Technology Data Exchange (ETDEWEB)

Heinemeyer, S. [Instituto de Fisica de Cantabria (CSIC-UC), Santander (Spain); Khoze, V.A. [Durham Univ. (United Kingdom). IPPP; Manchester Univ. (United Kingdom). School of Physics and Astronomy; Ryskin, M.G. [Durham Univ. (United Kingdom). IPPP; Petersburg Nuclear Physics Institute, St. Petersburg (Russian Federation); Tasevsky, M. [Institute of Physics, Prague (Czech Republic); Weiglein, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2010-12-15

We investigate the prospects for Central Exclusive Diffractive (CED) production of BSM Higgs bosons at the LHC using forward proton detectors installed at 220 m and 420 m distance around ATLAS and/or CMS. We update a previous analysis for the MSSM taking into account improvements in the theoretical calculations and the most recent exclusion bounds from the Tevatron. We extend the MSSM analysis to new benchmark scenarios that are in agreement with the cold dark matter relic abundance and other precision measurements. We analyse the exclusive production of Higgs bosons in a model with a fourth generation of fermions. Finally, we comment on the determination of Higgs spin-parity and coupling structures at the LHC and show that the forward proton mode could provide crucial information on the CP properties of the Higgs bosons. (orig.)

Discovery of the Higgs boson

CERN Document Server

Sharma, Vivek

2016-01-01

The recent observation of the Higgs boson has been hailed as the scientific discovery of the century and led to the 2013 Nobel Prize in physics. This book describes the detailed science behind the decades-long search for this elusive particle at the Large Electron Positron Collider at CERN and at the Tevatron at Fermilab and its subsequent discovery and characterization at the Large Hadron Collider at CERN. Written by physicists who played leading roles in this epic search and discovery, this book is an authoritative and pedagogical exposition of the portrait of the Higgs boson that has emerged from a large number of experimental measurements. As the first of its kind, this book should be of interest to graduate students and researchers in particle physics.

Seeking heavy Higgs bosons through cascade decays

Science.gov (United States)

Coleppa, Baradhwaj; Fuks, Benjamin; Poulose, P.; Sahoo, Shibananda

2018-04-01

We investigate the LHC discovery prospects for a heavy Higgs boson decaying into the standard model Higgs boson and additional weak bosons. We consider a generic model-independent new physics configuration where this decay proceeds via a cascade involving other intermediate scalar bosons and focus on an LHC final-state signature comprised either of four b -jets and two charged leptons or of four charged leptons and two b -jets. We design two analyses of the corresponding signals, and demonstrate that a 5 σ discovery at the 14 TeV LHC is possible for various combinations of the parent and daughter Higgs-boson masses. We moreover find that the standard model backgrounds can be sufficiently rejected to guarantee the reconstruction of the parent Higgs boson mass. We apply our analyses to the Type-II two-Higgs-doublet model and identify the regions of the parameter space to which the LHC is sensitive.

Topological Higgs mechanism with ordinary Higgs mechanism

International Nuclear Information System (INIS)

Oda Ichiro; Yahikozawa Shigeaki.

1989-12-01

Topological Higgs mechanism in higher dimensions is analyzed when ordinary Higgs potential exists. It is shown that if one-form B-field becomes massive by the ordinary Higgs mechanism, another D-2 form C-field also becomes massive through topological term in addition to the topological mass generation by the topological Higgs mechanism. Moreover we investigate this mechanism in three dimensional theories, that is to say, Chern-Simons theory and more general theory. (author). 10 refs

Higgs bosons in the two-doublet model with CP violation

International Nuclear Information System (INIS)

Akhmetzyanova, E.; Dolgopolov, M.; Dubinin, M.

2005-01-01

We consider the effective two-Higgs-doublet potential with complex parameters, when the CP invariance is broken both explicitly and spontaneously. The diagonal mass term in the local minimum of the potential is constructed for the physical basis of Higgs fields, keeping explicitly the limiting case of CP conservation, if the parameters are taken real. For the special case of the two-doublet Higgs sector of the minimal supersymmetric model, when CP invariance is violated by the Higgs bosons interaction with scalar quarks of the third generation, we calculate by means of the effective potential method the Higgs boson masses and evaluate the two-fermion Higgs boson decay widths and the widths of rare one-loop-mediated decays H→γγ, H→gg

Higgs-Yukawa model with higher dimension operators via extended mean field theory

CERN Document Server

Akerlund, Oscar

2016-01-01

Using Extended Mean Field Theory (EMFT) on the lattice, we study properties of the Higgs-Yukawa model as an approximation of the Standard Model Higgs sector, and the effect of higher dimension operators. We note that the discussion of vacuum stability is completely modified in the presence of a $\\phi^6$ term, and that the Higgs mass no longer appears fine tuned. We also study the finite temperature transition. Without higher dimension operators the transition is found to be second order (crossover with gauge fields) for the experimental value of the Higgs mass $M_h=125$ GeV. By taking a $\\phi^6$ interaction in the Higgs potential as a proxy for a UV completion of the Standard Model, the transition becomes stronger and turns first order if the scale of new physics, i.e. the mass of the lightest mediator particle, is around $1.5$ TeV. This implies that electroweak baryogenesis may be viable in models which introduce new particles around that scale.

Higgs boson theory and phenomenology mass measurements and nuclear physics Recent results from ISOLTRAP

CERN Document Server

Carena, M S; Herfurth, F; Ames, F; Audi, G; Beck, D; Blaum, K; Bollen, G; Kellerbauer, A G; Kluge, H J; Kuckein, M; Lunney, M D; Moore, R B; Oinonen, M; Rodríguez, D; Sauvan, E; Scheidenberger, C

2003-01-01

Precision electroweak data presently-favors a weakly-coupled Higgs sector as the mechanism responsible for electroweak symmetry breaking. Low-energy supersymmetry provides a natural framework for weakly-coupled elementary scalars. In this review, we summarize the theoretical properties of the Standard Model (SM) Higgs boson and the Higgs sector of the minimal super-symmetric extension of the Standard Model (MSSM). We then survey the phenomenology of the SM and MSSM Higgs bosons at the Tevatron, LHC and a future e**+e**- linear collider. We focus on the Higgs discovery potential of present and future colliders and stress the importance of precision measurements of Higgs boson properties. 459 Refs.31 The Penning trap mass spectrometer ISOLTRAP is a facility for high- precision mass measurements of short-lived radioactive nuclei installed at ISOLDE/CERN in Geneva. More than 200 masses have been measured with relative uncertainties of 1 multiplied by 10**-**7 or even close to 1 multiplied by 10**-**8 in special c...

Distinguishing a SM-like MSSM Higgs boson from SM Higgs boson at muon collider

International Nuclear Information System (INIS)

Singhal, Jai Kumar; Singh, Sardar; Nagawat, Ashok K.

2007-01-01

We explore the possibility of distinguishing the SM-like MSSM Higgs boson from the SM Higgs boson via Higgs boson pair production at future muon collider. We study the behavior of the production cross-section in SM and MSSM with Higgs boson mass for various MSSM parameters tanβ and m A . We observe that at fixed CM energy, in the SM, the total cross-section increases with the increase in Higgs boson mass whereas this trend is reversed for the MSSM. The changes that occur for the MSSM in comparison to the SM predictions are quantified in terms of the relative percentage deviation in cross-section. The observed deviations in cross-section for different choices of Higgs boson masses suggest that the measurements of the cross-section could possibly distinguish the SM-like MSSM Higgs boson from the SM Higgs boson. (author)

Intermediate- and heavy-Higgs-boson physics at a 0.5 TeV e+e- collider

International Nuclear Information System (INIS)

Barger, V.; Cheung, K.; Kniehl, B.A.; Phillips, R.J.N.

1992-01-01

We explore the potential of a future e + e- collider in the 0.5 TeV center-of-mass energy range to detect intermediate or heavy Higgs bosons in the standard model. We first briefly assess the logistics for finding a Higgs boson of intermediate mass, with M Z H W . We then study in detail the possibility of detecting a heavy Higgs boson, with m H >2M W , through the production of pairs of weak bosons. We quantitatively analyze the sensitivity of the process e + e-→ν bar νW + W-(ZZ) to the presence of a heavy-Higgs-boson resonance in the standard model. We compare this signal to various backgrounds and to the smaller signal from e + e-→ZH→μ + μ - W+W-(ZZ), assuming the weak-boson pairs to be detected and measured in their dominant hadronic decay modes W + W-(ZZ)→4 jets. A related Higgs-boson signal in 6-jet final states is also estimated. We show how the main backgrounds from e + e-W+W-(ZZ), eνWZ, and t bar t production can be reduced by suitable acceptance cuts. Bremsstrahlung and typical beamstrahlung corrections are calculated. These corrections reduce Higgs-boson production by scattering mechanisms but increase production by annihilation mechanisms; they also smear out some dynamical features such as Jacobian peaks in p T (H). With all these corrections included, we conclude that it should be possible to detect a heavy-Higgs-boson signal in the ν bar νW + W-(ZZ) channels up to mass m H =350 GeV

Exclusive weak radiative Higgs decays in the standard model and beyond

Energy Technology Data Exchange (ETDEWEB)

Alte, Stefan; König, Matthias [PRISMA Cluster of Excellence & Mainz Institute for Theoretical Physics,Johannes Gutenberg University,55099 Mainz (Germany); Neubert, Matthias [PRISMA Cluster of Excellence & Mainz Institute for Theoretical Physics,Johannes Gutenberg University,55099 Mainz (Germany); Department of Physics, LEPP, Cornell University,Ithaca, NY 14853 (United States)

2016-12-12

We perform a detailed study of the exclusive Higgs decays h→MZ and h→MW, where M is a pseudoscalar or vector meson, using the QCD factorization approach. We allow for the presence of new-physics effects in the form of modified Higgs couplings to gauge bosons and fermions, including the possibility of flavor-changing Higgs couplings. We show that the decays h→VZ exhibit a strong sensitivity to the effective CP-even and CP-odd hγZ couplings. When combined with a measurement of the h→γZ decay rate, this can be used to extract these couplings up to a sign ambiguity in the CP-odd coefficient. Some of the h→MW decay modes can be used to probe for flavor-violating Higgs couplings involving the top quark.

Structure of potentials with N Higgs doublets

International Nuclear Information System (INIS)

Nishi, C. C.

2007-01-01

Extensions of the standard model with N Higgs doublets are simple extensions presenting a rich mathematical structure. An underlying Minkowski structure emerges from the study of both variable space and parameter space. The former can be completely parametrized in terms of two future lightlike Minkowski vectors with spatial parts forming an angle whose cosine is -(N-1) -1 . For the parameter space, the Minkowski parametrization enables one to impose sufficient conditions for bounded below potentials, characterize certain classes of local minima, and distinguish charge breaking vacua from neutral vacua. A particular class of neutral minima presents a degenerate mass spectrum for the physical charged Higgs bosons

Electroweak phase transition in two Higgs doublet models

International Nuclear Information System (INIS)

Cline, J.M.; Lemieux, P.

1997-01-01

We reexamine the strength of the first-order phase transition in the electroweak theory supplemented by an extra Higgs doublet. The finite-temperature effective potential V eff is computed to one-loop order, including the summation of ring diagrams, to study the ratio φ c /T c of the Higgs field VEV to the critical temperature. We make a number of improvements over previous treatments, including a consistent treatment of Goldstone bosons in V eff , an accurate analytic approximation to V eff valid for any mass-to-temperature ratios, and use of the experimentally measured top quark mass. For two-Higgs-doublet models, we identify a significant region of parameter space where φ c /T c is large enough for electroweak baryogenesis, and we argue that this identification should persist even at higher orders in perturbation theory. In the case of the minimal supersymmetric standard model, our results indicate that the extra Higgs bosons have little effect on the strength of the phase transition. copyright 1997 The American Physical Society

Exclusive Higgs production at the LHC

Energy Technology Data Exchange (ETDEWEB)

Dechambre, Alice [Universite de Liege, Institut d' Astrophysique et de Geophysique, Allee du 6 aout, 17 - Bat. B5c, B-4000 Liege 1 - Sart-Tilman (Belgium); Staszewski, Rafal [IRFU/SPP, CEA-Saclay, bat. 141, 91191 Gif-sur-Yvette Cedex (France); Henryk Niewodniczanski, Institute of Nuclear Physics - PAN, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Krakow (Poland); Royon, Christophe [IRFU/SPP, CEA-Saclay, bat. 141, 91191 Gif-sur-Yvette Cedex (France)

2010-07-01

After a brief description of the models of exclusive diffractive Higgs production, we first evaluate the theoretical uncertainties that affect the calculation of exclusive cross section (jets, Higgs...). In addition, in view of the recent measurement of exclusive di-jet at CDF and the new implementation of the corresponding cross section in FPMC (Forward Physics Monte-Carlo), we developed an analysis strategy that can be used to narrow down these uncertainties with the help of early LHC measurement. (authors)

Vector Higgs-portal dark matter and the invisible Higgs

International Nuclear Information System (INIS)

Lebedev, Oleg; Lee, Hyun Min; Mambrini, Yann

2011-11-01

The Higgs sector of the Standard Model offers a unique probe of the hidden sector. In this work, we explore the possibility of renormalizable Higgs couplings to the hidden sector vector fields which can constitute dark matter (DM). Abelian gauge sectors with minimal field content, necessary to render the gauge fields massive, have a natural Z 2 parity. This symmetry ensures stability of the vector fields making them viable dark matter candidates, while evading the usual electroweak constraints. We illustrate this idea with the Stueckelberg and Higgs mechanisms. Vector DM is consistent with the WMAP, XENON100, and LHC constraints, while it can affect significantly the invisible Higgs decay. Due to the enhanced branching ratio for the Higgs decay into the longitudinal components of the vector field, the vector Higgs portal provides an efficient way to hide the Higgs at the LHC. This could be the reason why the latest combined ATLAS/CMS data did not bring evidence for the existence of the Higgs boson. (orig.)

Vector Higgs portal dark matter and the invisible Higgs

International Nuclear Information System (INIS)

Lebedev, Oleg; Lee, Hyun Min; Mambrini, Yann

2012-01-01

The Higgs sector of the Standard Model offers a unique probe of the hidden sector. In this work, we explore the possibility of renormalizable Higgs couplings to the hidden sector vector fields which can constitute dark matter (DM). Abelian gauge sectors with minimal field content, necessary to render the gauge fields massive, have a natural Z 2 parity. This symmetry ensures stability of the vector fields making them viable dark matter candidates, while evading the usual electroweak constraints. We illustrate this idea with the Stückelberg and Higgs mechanisms. Vector DM is consistent with the WMAP, XENON100, and LHC constraints, while it can affect significantly the invisible Higgs decay. Due to the enhanced branching ratio for the Higgs decay into the longitudinal components of the vector field, the vector Higgs portal provides an efficient way to hide the Higgs at the LHC. This could be the reason why the latest combined ATLAS/CMS data did not bring evidence for the existence of the Higgs boson.

Vector Higgs-portal dark matter and the invisible Higgs

Energy Technology Data Exchange (ETDEWEB)

Lebedev, Oleg [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Lee, Hyun Min [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Mambrini, Yann [Paris-Sud Univ., 91 - Orsay (France). Lab. de Physique Theorique

2011-11-15

The Higgs sector of the Standard Model offers a unique probe of the hidden sector. In this work, we explore the possibility of renormalizable Higgs couplings to the hidden sector vector fields which can constitute dark matter (DM). Abelian gauge sectors with minimal field content, necessary to render the gauge fields massive, have a natural Z{sub 2} parity. This symmetry ensures stability of the vector fields making them viable dark matter candidates, while evading the usual electroweak constraints. We illustrate this idea with the Stueckelberg and Higgs mechanisms. Vector DM is consistent with the WMAP, XENON100, and LHC constraints, while it can affect significantly the invisible Higgs decay. Due to the enhanced branching ratio for the Higgs decay into the longitudinal components of the vector field, the vector Higgs portal provides an efficient way to hide the Higgs at the LHC. This could be the reason why the latest combined ATLAS/CMS data did not bring evidence for the existence of the Higgs boson. (orig.)

Higgs Boson Properties in the Standard Model and its Supersymmetric Extensions

CERN Document Server

Ellis, Jonathan Richard; Zwirner, F; Ellis, John; Ridolfi, Giovanni; Zwirner, Fabio

2007-01-01

We review the realization of the Brout-Englert-Higgs mechanism in the electroweak theory and describe the experimental and theoretical constraints on the mass of the single Higgs boson expected in the minimal Standard Model. We also discuss the couplings of this Higgs boson and its possible decay modes as functions of its unknown mass. We then review the structure of the Higgs sector in the minimal supersymmetric extension of the Standard Model (MSSM), noting the importance of loop corrections to the masses of its five physical Higgs bosons. Finally, we discuss some non-minimal models.

Higgs boson properties in the Standard Model and its supersymmetric extensions

International Nuclear Information System (INIS)

Ellis, J.; Ridolfi, G.; Zwirner, F.

2007-01-01

We review the realization of the Brout-Englert-Higgs mechanism in the electroweak theory and describe the experimental and theoretical constraints on the mass of the single Higgs boson expected in the minimal Standard Model. We also discuss the couplings of this Higgs boson and its possible decay modes as functions of its unknown mass. We then review the structure of the Higgs sector in the minimal supersymmetric extension of the Standard Model (MSSM), noting the importance of loop corrections to the masses of its 5 physical Higgs bosons. Finally, we discuss some non-minimal models. (authors)

The ATLAS Higgs machine learning challenge

CERN Document Server

Davey, W; The ATLAS collaboration; Rousseau, D; Cowan, G; Kegl, B; Germain-Renaud, C; Guyon, I

2014-01-01

High Energy Physics has been using Machine Learning techniques (commonly known as Multivariate Analysis) since the 90's with Artificial Neural Net for example, more recently with Boosted Decision Trees, Random Forest etc... Meanwhile, Machine Learning has become a full blown field of computer science. With the emergence of Big Data, Data Scientists are developing new Machine Learning algorithms to extract sense from large heterogeneous data. HEP has exciting and difficult problems like the extraction of the Higgs boson signal, data scientists have advanced algorithms: the goal of the HiggsML project is to bring the two together by a “challenge”: participants from all over the world and any scientific background can compete online ( https://www.kaggle.com/c/higgs-boson ) to obtain the best Higgs to tau tau signal significance on a set of ATLAS full simulated Monte Carlo signal and background. Winners with the best scores will receive money prizes ; authors of the best method (most usable) will be invited t...

Recent developments in HiggsBounds and a preview of HiggsSignals

Energy Technology Data Exchange (ETDEWEB)

Bechtle, Philip; Stefaniak, Tim; Williams, Karina [Bonn Univ. (Germany). Physikalisches Inst.; Heinemeyer, Sven [Instituto de Fisica de Cantabria (CSIC-UC), Santander (Spain); Staal, Oscar [Stockholm Univ. (Sweden). Dept. of Physics; Weiglein, Georg [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Brein, Oliver

2013-01-15

We report on recent developments in the public computer code HiggsBounds, which confronts arbitrary Higgs sector predictions with 95% C.L. exclusion limits from Higgs searches at the LEP, Tevatron and LHC experiments. We discuss in detail the performance of the Standard Model (SM) likeness test as implemented in the latest version HiggsBounds-3.8.0, whose outcome decides whether a search for a SM Higgs boson can be applied to a model beyond the SM. Furthermore, we give a preview of features in the upcoming version HiggsBounds-4.0.0 and the new program HiggsSignals, which performs a {chi}{sup 2} test of Higgs sector predictions against the signal rate and mass measurements from Higgs boson analyses at the Tevatron and LHC. This is illustrated with an example where the heavier CP-even Higgs boson of the Minimal Supersymmetric Standard Model (MSSM) is considered as an explanation of the LHC Higgs signal at {approx_equal} 126 GeV.

Flavor changing heavy Higgs interactions at the LHC

Directory of Open Access Journals (Sweden)

Baris Altunkaynak

2015-12-01

Full Text Available A general two Higgs doublet model (2HDM is adopted to study the signature of flavor changing neutral Higgs (FCNH decay ϕ0→tc¯+t¯c, where ϕ0 could be a CP-even scalar (H0 or a CP-odd pseudoscalar (A0. Measurement of the light 125 GeV neutral Higgs boson (h0 couplings at the Large Hadron Collider (LHC favor the decoupling limit or the alignment limit of a 2HDM, in which gauge boson and diagonal fermion couplings of h0 approach Standard Model values. In such limit, FCNH couplings of h0 are naturally suppressed by a small mixing parameter cos⁡(β−α, while the off-diagonal couplings of heavier neutral scalars ϕ0 are sustained by sin⁡(β−α∼1. We study physics background from dominant processes with realistic acceptance cuts and tagging efficiencies. Promising results are found for the LHC running at 13 or 14 TeV collision energies.

Beyond the standard Higgs at the LHC. Present constraints on little Higgs models and future prospects

International Nuclear Information System (INIS)

Tonini, Marco

2014-11-01

This thesis discusses the consistency of different Little Higgs models with the collected collider data as of the summer of 2013. Moreover, future prospects for possible discoveries and mass measurement methods of new physics signals at the foreseen LHC run II with increased center-of-mass energy are presented. Little Higgs models belong to a class of extensions of the Standard Higgs model, predicting a strong interaction regime at a compositeness scale Λ=4πf approximate global symmetry spontaneously broken at the scale f. A natural hierarchy between the compositeness and the electroweak scale is introduced by the Collective Symmetry Breaking mechanism: one-loop diagrams generating the Higgs mass term are forced to be at most logarithmically sensitive to Λ. A naturally light Higgs boson can thus be accommodated, consistently with a perturbative theory until a scale of order 10 TeV. We have probed the parameter space of three prominent examples of Little Higgs models, namely the Simplest Little Higgs model, the Littlest Higgs model, and the Littlest Higgs model with T-parity, against electroweak precision observables and the collected LHC data concerning both Higgs properties and direct searches for new particles, with √(s)=7,8 TeV and up to 25 fb -1 of integrated luminosity. Lower bounds on the scale f are set, within a certain degree of confidence level, which allow to draw conclusions on the ''naturalness'' of the different models. Optimisations of the existing direct searches setups, assuming a Little Higgs signal, as well as dedicated mass measurement methods designed for the foreseen LHC runs with √(s)=13,14 TeV are thoroughly discussed and proposed in this thesis. Special attention will be dedicated to final states including either a large or negligible fraction of missing transverse momentum. In particular, we will propose a dedicated collider search tailored for the discovery and mass measurement of a top partner, exploiting jet

The Higgs mechanism and the origin of mass

Science.gov (United States)

Djouadi, Abdelhak

2012-06-01

The Higgs mechanism plays a key role in the physics of elementary particles: in the context of the Standard Model, the theory which describes in a unified framework the electromagnetic, weak and strong nuclear interactions, it allows for the generation of particle masses while preserving the fundamental symmetries of the theory. This mechanism predicts the existence of a new type of particle, the scalar Higgs boson, with unique characteristics. The detection of this particle and the study of its fundamental properties is a major goal of high-energy particle colliders, such as the CERN Large Hadron Collider or LHC.

Studies of the SM Higgs boson and searches for BSM Higgs bosons with the ATLAS Detector

CERN Document Server

AUTHOR|(INSPIRE)INSPIRE-00182253; The ATLAS collaboration

2016-01-01

The ATLAS collaboration has searched for the Standard Model Higgs Boson in the first LHC Run-2 data using 3.2 $fb^{-1}$ at 13 TeV. Results are presented in terms of central value and limits on the total cross-section in the 4l and $\\gamma\\gamma$ channels. Several "Beyond Standard Model" theories predict the existence of additional heavy Higgs particles or di-Higgs resonances. Searches are conducted using the $\\gamma\\gamma$, ZZ, WW and fermionic decay channels, and cover a large range of masses for the hypothetical resonances.

Searches for the Higgs Boson with the ATLAS detector at the LHC

International Nuclear Information System (INIS)

Mazini, Rachid

2007-01-01

Searching for the Higgs boson lies at the heart of the physics program of the Large Hadron Collider (LHC). The prospects for Higgs searches with the ATLAS detector at the LHC are reviewed. The discovery potential of most prominent Higgs final states predicted by the Standard Model and the MSSM are reviewed. (Author)

A Search for Neutral Supersymmetric Higgs Bosons at DØ

Energy Technology Data Exchange (ETDEWEB)

Osman, Nicolas Ahmed [Imperial College, London (United Kingdom)

2010-09-01

A search for Higgs bosons in multijet data from the DØ detector is reported in this thesis. The Higgs boson is the only remaining undiscovered particle in the Standard Model of particle physics, and plays an integral role in this model. It is known that this model is not a complete description of fundamental physics (it does not describe gravity, for example), and so searches for physics beyond the Standard Model are an important part of particle physics. One extension of the Standard Model, the Minimal Supersymmetric Standard Model (MSSM), predicts the existence of five Higgs bosons, two of which can show an enhanced coupling to bottom quarks. For this reason, a search in the bbb (multijet) channel is a sensitive test of Higgs boson physics. The analysis described in this thesis was conducted over 6.6 fb^-1 of data. At the time of writing, the best limits on tan β (a key parameter of the MSSM) in the multijet channel were set by DØ. The new analysis described in this thesis included more data than the previous analysis in the channel, and made use of a new trigger and event-based analysis method. An improved Multivariate Analysis technique was used to separate signal and background events and produce a final discriminant for the limit setting process. These changes increased the expected sensitivity of this measurement by roughly 50% more than would be expected from the increase in the size of data sample alone.

Higgs boson from an extended symmetry

International Nuclear Information System (INIS)

Barbieri, Riccardo; Bellazzini, Brando; Rychkov, Vyacheslav S.; Varagnolo, Alvise

2007-01-01

The variety of ideas put forward in the context of a composite picture for the Higgs boson calls for a simple and effective description of the related phenomenology. Such a description is given here by means of a minimal model and is explicitly applied to the example of a Higgs-top sector from an SO(5) symmetry. We discuss the spectrum, the electroweak precision tests, B-physics, and naturalness. We show the difficulty in complying with the different constraints. The extended gauge sector relative to the standard SU(2)xU(1), if there is any, has little or no impact on these considerations. We also discuss the relation of the minimal model with its 'little Higgs' or holographic extensions based on the same symmetry

Study of the physics potential of the FCC-hh machine to measure the coupling of the Higgs boson to b quarks

CERN Document Server

Rodríguez, Arturo

2016-01-01

The FCC project as well as the Pythia + Delphes analysis within the FCC software are introduced. The ROOT analysis carried out to reconstruct main observables, such the invariant mass of the bb system, transverse mass and momentum of the W boson together with the lepton pT and distribution is explained. The resulting reconstructed invariant mass of the bb system showed a peak near the 125 GeV in correspondence with the Higgs boson. Future steps towards estimating the physics potential of the FCC-hh machine in this channel are discussed.

Dirichlet Higgs in Extra-Dimension Consistent with Electroweak Data

International Nuclear Information System (INIS)

Naoyuki Habay; Kin-ya Odaz; Ryo Takahashi

2011-01-01

We propose a simple five-dimensional extension of the Standard Model (SM) without any Higgs potential nor any extra fields. A Higgs doublet lives in the bulk of a flat line segment and its boundary condition is Dirichlet at the ends of the line, which causes the electroweak symmetry breaking without Higgs potential. The vacuum expectation value of the Higgs is induced from the Dirichlet boundary condition which is generally allowed in higher dimensional theories. The lightest physical Higgs has non-flat profile in the extra dimension even though the vacuum expectation value is flat. As a consequence, we predict a maximal top Yukawa deviation (no coupling between top and Higgs) for the brane-localized fermion and a small deviation, a multiplication of 2√2/π ≅ 0.9 to the Yukawa coupling, for the bulk fermion. The latter is consistent with the electroweak precision data within 90% C.L. for 430 GeV ≤ m KK ≤ 500 GeV. (authors)

Improved Limits for Higgs-Portal Dark Matter from LHC Searches.

Science.gov (United States)

Hoferichter, Martin; Klos, Philipp; Menéndez, Javier; Schwenk, Achim

2017-11-03

Searches for invisible Higgs decays at the Large Hadron Collider constrain dark matter Higgs-portal models, where dark matter interacts with the standard model fields via the Higgs boson. While these searches complement dark matter direct-detection experiments, a comparison of the two limits depends on the coupling of the Higgs boson to the nucleons forming the direct-detection nuclear target, typically parametrized in a single quantity f_{N}. We evaluate f_{N} using recent phenomenological and lattice-QCD calculations, and include for the first time the coupling of the Higgs boson to two nucleons via pion-exchange currents. We observe a partial cancellation for Higgs-portal models that makes the two-nucleon contribution anomalously small. Our results, summarized as f_{N}=0.308(18), show that the uncertainty of the Higgs-nucleon coupling has been vastly overestimated in the past. The improved limits highlight that state-of-the-art nuclear physics input is key to fully exploiting experimental searches.

Higgs pair production in the CP-violating two-Higgs-doublet model

Science.gov (United States)

Bian, Ligong; Chen, Ning; Jiang, Yun

2017-12-01

The SM-like Higgs pair production is discussed in the framework of the general CP-violating two-Higgs-doublet model, where we find that the CP-violating mixing angles can be related to the Higgs self-couplings. Therefore, the future experimental searches for Higgs boson pairs can be constrained by the improved precision of the electric dipole moment measurements. Based on a series of constraints of the SM-like Higgs boson signal fits, the perturbative unitarity and stability bounds to the Higgs potential, and the most recent LHC searches for heavy Higgs bosons, we suggest a set of benchmark models for the future high-energy collider searches for Higgs pair production. The e+e- colliders operating at s = (500GeV,1 TeV) are capable of measuring the Higgs cubic self-couplings of the benchmark models directly. We also estimate the cross sections of the resonance contributions to the Higgs pair productions for the benchmark models at the future LHC and SppC/FCC-hh runs.

Radiative corrections to the triple Higgs coupling in the inert Higgs doublet model

International Nuclear Information System (INIS)

Arhrib, Abdesslam; Benbrik, Rachid; Falaki, Jaouad El; Jueid, Adil

2015-01-01

We investigate the implication of the recent discovery of a Higgs-like particle in the first phase of the LHC Run 1 on the Inert Higgs Doublet Model (IHDM). The determination of the Higgs couplings to SM particles and its intrinsic properties will get improved during the new LHC Run 2 starting this year. The new LHC Run 2 would also shade some light on the triple Higgs coupling. Such measurement is very important in order to establish the details of the electroweak symmetry breaking mechanism. Given the importance of the Higgs couplings both at the LHC and e + e − Linear Collider machines, accurate theoretical predictions are required. We study the radiative corrections to the triple Higgs coupling hhh and to hZZ, hWW couplings in the context of the IHDM. By combining several theoretical and experimental constraints on parameter space, we show that extra particles might modify the triple Higgs coupling near threshold regions. Finally, we discuss the effect of these corrections on the double Higgs production signal at the e + e − LC and show that they can be rather important.

Integrating out the standard Higgs field in the path integral

International Nuclear Information System (INIS)

Dittmaier, S.

1996-01-01

We integrate out the Higgs boson in the electroweak standard model at one loop and construct a low-energy effective Lagrangian assuming that the Higgs mass is much larger than the gauge-boson masses. Instead of applying diagrammatical techniques, we integrate out the Higgs boson directly in the path integral, which turns out to be much simpler. By using the background-field method and the Stueckelberg formalism, we directly find a manifestly gauge-invariant result. The heavy-Higgs effects on fermionic couplings are derived, too. At one loop the log M H terms of the heavy-Higgs limit of the electroweak standard model coincide with the UV-divergent terms in the gauged non-linear σ-model, but vertex functions differ in addition by finite constant terms. Finally, the leading Higgs effects to some physical processes are calculated from the effective Lagrangian. (orig.)

Superhorizon electromagnetic field background from Higgs loops in inflation

Science.gov (United States)

Kaya, Ali

2018-03-01

If Higgs is a spectator scalar, i.e. if it is not directly coupled to the inflaton, superhorizon Higgs modes must have been exited during inflation. Since Higgs is unstable its decay into photons is expected to seed superhorizon photon modes. We use in-in perturbation theory to show that this naive physical expectation is indeed fulfilled via loop effects. Specifically, we calculate the first order Higgs loop correction to the magnetic field power spectrum evaluated at some late time after inflation. It turns out that this loop correction becomes much larger than the tree-level power spectrum at the superhorizon scales. This suggests a mechanism to generate cosmologically interesting superhorizon vector modes by scalar-vector interactions.

Double elementary Goldstone Higgs boson production in future linear colliders

Science.gov (United States)

Guo, Yu-Chen; Yue, Chong-Xing; Liu, Zhi-Cheng

2018-03-01

The Elementary Goldstone Higgs (EGH) model is a perturbative extension of the Standard Model (SM), which identifies the EGH boson as the observed Higgs boson. In this paper, we study pair production of the EGH boson in future linear electron positron colliders. The cross-sections in the TeV region can be changed to about ‑27%, 163% and ‑34% for the e+e‑→ Zhh, e+e‑→ νν¯hh and e+e‑→ tt¯hh processes with respect to the SM predictions, respectively. According to the expected measurement precisions, such correction effects might be observed in future linear colliders. In addition, we compare the cross-sections of double SM-like Higgs boson production with the predictions in other new physics models.

Implications for new physics from fine-tuning arguments: II. Little Higgs models

International Nuclear Information System (INIS)

Casas, J.A.; Espinosa, J.R.; Hidalgo, I.

2005-01-01

We examine the fine-tuning associated to electroweak breaking in Little Higgs scenarios and find it to be always substantial and, generically, much higher than suggested by the rough estimates usually made. This is due to implicit tunings between parameters that can be overlooked at first glance but show up in a more systematic analysis. Focusing on four popular and representative Little Higgs scenarios, we find that the fine-tuning is essentially comparable to that of the Little Hierarchy problem of the Standard Model (which these scenarios attempt to solve) and higher than in supersymmetric models. This does not demonstrate that all Little Higgs models are fine-tuned, but stresses the need of a careful analysis of this issue in model-building before claiming that a particular model is not fine-tuned. In this respect we identify the main sources of potential fine-tuning that should be watched out for, in order to construct a successful Little Higgs model, which seems to be a non-trivial goal. (author)

Electroweak Calibration of the Higgs Characterization Model

CERN Multimedia

CERN. Geneva

2015-01-01

I will present the preliminary results of histogram fits using the Higgs Combine histogram fitting package. These fits can be used to estimate the effects of electroweak contributions to the p p -> H mu+ mu- Higgs production channel and calibrate Beyond Standard Model (BSM) simulations which ignore these effects. I will emphasize my findings' significance in the context of other research here at CERN and in the broader world of high energy physics.

Jet energy measurements at ILC. Calorimeter DAQ requirements and application in Higgs boson mass measurements

International Nuclear Information System (INIS)

Ebrahimi, Aliakbar

2017-11-01

The idea of spontaneous symmetry breaking as the mechanism through which elementary particles gain mass has been confirmed by the discovery of the Higgs boson at the CERN Large Hadron Collider. Studying the Higgs boson properties are of great importance to verify the Standard Model predictions. Any deviation from these predictions could uncover physics beyond the Standard Model. The mass of the Higgs boson is one of the important parameters of the Standard Model. The precise determination of the Higgs boson mass is of interest in its own right and also for other Higgs physics studies since it enters as parametric uncertainty into the extraction of the partial width from branching ratio measurements. The International Linear Collider (ILC) is a future polarised e + e - collider designed for precision physics studies. The Higgs boson decay to a pair of bottom quarks H→b anti b has the largest branching ratio of all Higgs decays, providing a large dataset for physics analyses. The possibility of measuring the Higgs boson mass in the e + e - →ZH→q anti qb anti b channel is investigated in this thesis for centre-of-mass energies of 350 GeV and 500 GeV. Since the Higgs boson mass is reconstructed from two b jets, the jet energy resolution hasa high impact on the measurement. A new method to estimate the jet energy resolution for each jet individually is developed in this thesis. The jet-specific energy resolution is then used in the analysis for the Higgs boson mass measurements. Various strategies for the Higgs boson mass measurement are investigated. For an integrated luminosity of 1000 fb -1 and a beam polarisation of (-0.8,+0.3), statistical uncertainties of 42 MeV and 89 MeV are achieved for the centre-of-mass energies of 350 GeV and 500 GeV, respectively. Various sources of systematic uncertainties are also discussed. These results are obtained using a full GEANT4-based simulation of the International Large Detector (ILD) concept. The jet energy resolution

Jet energy measurements at ILC. Calorimeter DAQ requirements and application in Higgs boson mass measurements

Energy Technology Data Exchange (ETDEWEB)

Ebrahimi, Aliakbar

2017-11-15

The idea of spontaneous symmetry breaking as the mechanism through which elementary particles gain mass has been confirmed by the discovery of the Higgs boson at the CERN Large Hadron Collider. Studying the Higgs boson properties are of great importance to verify the Standard Model predictions. Any deviation from these predictions could uncover physics beyond the Standard Model. The mass of the Higgs boson is one of the important parameters of the Standard Model. The precise determination of the Higgs boson mass is of interest in its own right and also for other Higgs physics studies since it enters as parametric uncertainty into the extraction of the partial width from branching ratio measurements. The International Linear Collider (ILC) is a future polarised e{sup +}e{sup -} collider designed for precision physics studies. The Higgs boson decay to a pair of bottom quarks H→b anti b has the largest branching ratio of all Higgs decays, providing a large dataset for physics analyses. The possibility of measuring the Higgs boson mass in the e{sup +}e{sup -}→ZH→q anti qb anti b channel is investigated in this thesis for centre-of-mass energies of 350 GeV and 500 GeV. Since the Higgs boson mass is reconstructed from two b jets, the jet energy resolution hasa high impact on the measurement. A new method to estimate the jet energy resolution for each jet individually is developed in this thesis. The jet-specific energy resolution is then used in the analysis for the Higgs boson mass measurements. Various strategies for the Higgs boson mass measurement are investigated. For an integrated luminosity of 1000 fb{sup -1} and a beam polarisation of (-0.8,+0.3), statistical uncertainties of 42 MeV and 89 MeV are achieved for the centre-of-mass energies of 350 GeV and 500 GeV, respectively. Various sources of systematic uncertainties are also discussed. These results are obtained using a full GEANT4-based simulation of the International Large Detector (ILD) concept. The

Handbook of LHC Higgs Cross Sections: 2. Differential Distributions

CERN Document Server

Dittmaier, S; Passarino, G; Tanaka, R; Alekhin, S; Alwall, J; Bagnaschi, E A; Banfi, A; Blumlein, J; Bolognesi, S; Chanon, N; Cheng, T; Cieri, L; Cooper-Sarkar, A M; Cutajar, M; Dawson, S; Davies, G; De Filippis, N; Degrassi, G; Denner, A; D'Enterria, D; Diglio, S; Di Micco, B; Di Nardo, R; Ellis, R K; Farilla, A; Farrington, S; Felcini, M; Ferrera, G; Flechl, M; de Florian, D; Forte, S; Ganjour, S; Garzelli, M V; Gascon-Shotkin, S; Glazov, S; Goria, S; Grazzini, M; Guillet, J -Ph; Hackstein, C; Hamilton, K; Harlander, R; Hauru, M; Heinemeyer, S; Hoche, S; Huston, J; Jackson, C; Jimenez-Delgado, P; Jorgensen, M D; Kado, M; Kallweit, S; Kardos, A; Kauer, N; Kim, H; Kovac, M; Kramer, M; Krauss, F; Kuo, C -M; Lehti, S; Li, Q; Lorenzo, N; Maltoni, F; Mellado, B; Moch, S O; Muck, A; Muhlleitner, M; Nadolsky, P; Nason, P; Neu, C; Nikitenko, A; Oleari, C; Olsen, J; Palmer, S; Paganis, S; Papadopoulos, C G; Petersen, T C; Petriello, F; Petrucci, F; Piacquadio, G; Pilon, E; Potter, C T; Price, J; Puljak, I; Quayle, W; Radescu, V; Rebuzzi, D; Reina, L; Rojo, J; Rosco, D; Salam, G P; Sapronov, A; Schaarschmidt, J; Schonherr, M; Schumacher, M; Siegert, F; Slavich, P; Spira, M; Stewart, I W; Stirling, W J; Stockli, F; Sturm, C; Tackmann, F J; Thorne, R S; Tommasini, D; Torrielli, P; Tramontano, F; Trocsanyi, Z; Ubiali, M; Uccirati, S; Acosta, M Vazquez; Vickey, T; Vicini, A; Waalewijn, W J; Wackeroth, D; Warsinsky, M; Weber, M; Wiesemann, M; Weiglein, G; Yu, J; Zanderighi, G

2012-01-01

This Report summarises the results of the second year's activities of the LHC Higgs Cross Section Working Group. The main goal of the working group was to present the state of the art of Higgs Physics at the LHC, integrating all new results that have appeared in the last few years. The first working group report Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002) focuses on predictions (central values and errors) for total Higgs production cross sections and Higgs branching ratios in the Standard Model and its minimal supersymmetric extension, covering also related issues such as Monte Carlo generators, parton distribution functions, and pseudo-observables. This second Report represents the next natural step towards realistic predictions upon providing results on cross sections with benchmark cuts, differential distributions, details of specific decay channels, and further recent developments.

The 4D Composite Higgs

CERN Document Server

De Curtis, Stefania; Tesi, Andrea

2012-01-01

We propose a four dimensional description of Composite Higgs Models which represents a complete framework for the physics of the Higgs as a pseudo-Nambu-Goldstone boson. Our setup captures all the relevant features of 5D models and more in general of composite Higgs models with partial compositeness. We focus on the minimal scenario where we include a single multiplet of resonances of the composite sector, as these will be the only degrees of freedom which might be accessible at the LHC. This turns out to be sufficient to compute the effective potential and derive phenomenological consequences of the theory. Moreover our simplified approach is well adapted to simulate these models at the LHC. We also consider the impact of non-minimal terms in the effective lagrangian which do not descend from a 5D theory and could be of phenomenological relevance, for example contributing to the S-parameter.

Looking for the Charged Higgs Boson - Simulation Studies for the ATLAS Experiment

CERN Document Server

AUTHOR|(CDS)2073607

2009-01-01

The discovery of a charged Higgs boson (H+) would be an unambiguous sign of physics beyond the Standard Model. This thesis describes preparations for the H+ search with the ATLAS experiment at the Large Hadron Collider at CERN. The H+ discovery potential is evaluated, and tools for H+ searches are developed and refined. The $H^{+} \\to \\tau \

Anomaly mediated supersymmetric models and Higgs data from the LHC

CERN Document Server

Arbey, A; Mahmoudi, F; Tarhini, A

2013-01-01

Anomaly mediation models are well motivated supersymmetry breaking scenarios which appear as alternatives to the mSUGRA paradigm. These models are quite compelling from the theoretical point of view and it is therefore important to test if they are also viable models for phenomenology. We perform a study of these models in the light of all standard flavour, collider and dark matter constraints, including also the recent Higgs boson measurements for the mass and signal strengths in the different decay channels. The minimal AMSB scenario can satisfy in part of its parameter space the dark matter requirement but is only marginally consistent with the current Higgs boson mass value. The HyperCharge-AMSB and Mixed Moduli-AMSB scenarios can better describe present data from dark matter, flavour, low energy physics and are consistent with the measured mass of the Higgs boson. The inclusion of the preferred signal strengths for the Higgs boson decay channels shows that for tan(beta) > 5 the HC-AMSB and MM-AMSB models...

Quantum chromodynamics effects in electroweak and Higgs physics

Indian Academy of Sciences (India)

Several examples of the often intricate effects of higher-order quantum chromodynamics (QCD) corrections on predictions for hadron-collider observables, are discussed, using the production of electroweak gauge boson and the Standard Model Higgs boson as examples. Particular attention is given to the interplay of QCD ...

Evidence of Higgs Boson Production through Vector Boson Fusion

CERN Document Server

AUTHOR|(INSPIRE)INSPIRE-00333580

The discovery of the Higgs boson in 2012 provided confirmation of the proposed mechanism for preserving the electroweak $SU(2) \\times U(1)$ gauge symmetry of the Standard Model of particle physics. It also heralded in a new era of precision Higgs physics. This thesis presents a measurement of the rate at which the Higgs boson is produced by vector boson fusion in the \\wwlnln decay channel. With gauge boson couplings in both the production and decay vertices, a VBF measurement in this channel is a powerful probe of the $VVH$ vertex strength. Using $4.5$~fb$^{-1}$ and $20.3$~fb$^{-1}$ of $pp$ collision data collected at respective center-of-mass energies of 7 and $8 \\tev$ in the ATLAS detector, measurements of the statistical significance and the signal strength are carried out in the Higgs mass range $100 \\leq m_H \\leq 200 \\gev$. These measurements are enhanced with a boosted decision tree that exploits the correlations between eight kinematic inputs in order to separate signal and background processes. At the...

Effective approaches in and beyond the MSSM: applications to Higgs physics and dark matter observables

International Nuclear Information System (INIS)

Drieu la Rochelle, G.

2012-01-01

We have developed in this thesis a method to shed some light on the features of supersymmetry in view of Higgs physics and observables pertaining to dark matter: the effective approach. We have thus investigated the BMSSM framework, an extension of the MSSM - Minimal Supersymmetric Standard Model - that encompasses many different extensions of the MSSM. It turns out that allowing for extra-physics that affect the Higgs sector of the MSSM produces a much richer Higgs phenomenology compared to the MSSM. An important development that we have carried out in the aim of exploiting the LHC performance in the BMSSM framework is the recasting of the Standard Model analyses to BSM (Beyond the Standard Model) theories. Precisely, we have evaluated the accuracy of some approximations as for instance the quadrature sum of different signals to combine the statistical significances and the use of the inclusive predicted cross-sections instead of the exclusive ones. We have also seen that limits on the cross-sections that are obtained by a combination of different subchannels are generically model-dependent. We have then turned to another set of constraints on supersymmetric theories that consists in the dark matter observables. Our work has focused on the precise computation of the relic density in the MSSM. We have decided to introduce once again an effective approach, but whereas the one implemented in the BMSSM aimed at accounting for extra physics beyond the MSSM, this specific one was built to account for radiative corrections brought by MSSM particles. We have performed the implementation of different effective vertices and assessed the robustness of the approach in the case of annihilation of neutralinos to fermions. We have found that the full one-loop result was very well approximated in the case of a bi no-like neutralino, where the discrepancy between both calculations was found to be less than 2%. We have also discussed the case of the Higgsino's-like neutralino with

SM Higgs decay branching ratios and total Higgs width

CERN Multimedia

Daniel Denegri

2001-01-01

Upper: Higgs decay ratios as a function of Higgs mass. The largest branching ratio is not necessarily the most usefull one. The most usefull ones are gamma gamma bbar ZZ and WW as in those modes latter signal to background ratios can be achieved. Lower: Total Higgs decay width versus Higgs mass. At low masses the natural width is extremely small, thus observability depends on instrumental resolution primarily.

LFC15: physics prospects for linear and other future colliders after the discovery of the Higgs

CERN Document Server

De Curtis, Stefania; Moretti, Stefano; Pancheri, Giulia

2016-01-01

This workshop will explore the impact of QCD effects on the choice of future high energy accelerators, where to pursue effective studies of the BEH (Brout-Englert-Higgs) boson in view of ascertaining its true nature. We shall discuss the implications of the fact that its hadronic signatures are indeed the least accessible ones at present and examine possible origins of the BEH boson from physics Beyond the Standard Model. The workshop will include presentations from leading participants in studies of future projects, both Linear and Circular colliders, including Cosmic Ray projects as well. Comparison with LHC results from the coming run at 13 TeV and the future high luminosity option will highlight the new frontiers to explore.

submitter LEP Higgs

CERN Document Server

Mori, T

2001-01-01

As the LEP experiments verified the gauge interactions more and more rigorously, searches for the Higgs boson, which forms the very basis of the gauge theories, were taking on more and more importance in LEP physics. How this last missing particle in the Standard Model may be discovered (or totally excluded) will be the key to new physics beyond the Standard Model. Here I briefly describe how the LEP experiments together have closed in on this God particle during their 11 year running.

Study of Higgs self couplings of a supersymmetric E6 model at the international linear collider

International Nuclear Information System (INIS)

Ham, S. W.; Han, K. D.; Lee, J. I.; Oh, S. K.

2010-01-01

We study the Higgs self couplings of a supersymmetric E 6 model that has two Higgs doublets and two Higgs singlets. The lightest scalar Higgs boson in the model may be heavier than 112 GeV, at the one-loop level, where the negative results for the Higgs search at the LEP2 experiments are taken into account. The contributions from the top and scalar top quark loops are included in the radiative corrections to the one-loop mass of the lightest scalar Higgs boson in the effective potential approximation. The effect of the Higgs self couplings may be observed in the production of the lightest scalar Higgs bosons in e + e - collisions at the International Linear Collider (ILC) via the double Higgs-strahlung process. For the center of mass energy of 500 GeV with an integrated luminosity of 500 fb -1 and an efficiency of 20%, we expect that at least 5 events of the lightest scalar Higgs boson may be produced at the ILC via the double Higgs-strahlung process.

Study of the Higgs-Yukawa theory in the strong-Yukawa coupling regime

International Nuclear Information System (INIS)

Bulava, John; Gerhold, Philipp; Nagy, Attila; Deutsches Elektronen-Synchrotron; Hou, George W.S.; Smigielski, Brian; Jansen, Karl; Knippschild, Bastian; Univ. of Mainz; Lin, David C.J.; National Centre of Theoretical Sciences, Hsinchu; Nagai, Kei-Ichi; Ogawa, Kenji

2011-12-01

In this article, we present an ongoing lattice study of the Higgs-Yukawa model, in the regime of strong-Yukawa coupling, using overlap fermions. We investigated the phase structure in this regime by computing the Higgs vacuum expectation value, and by exploring the finite-size scaling behaviour of the susceptibility corresponding to the magnetisation. Our preliminary results indicate the existence of a second-order phase transition when the Yukawa coupling becomes large enough, at which the Higgs vacuum expectation value vanishes and the susceptibility diverges. (orig.)

A powerful tool for measuring Higgs boson associated Lepton Flavour Violation

International Nuclear Information System (INIS)

Kanemura, Shinya; Tsumura, Koji

2009-01-01

In models with extended Higgs sectors, Higgs-boson-mediated Lepton Flavour Violation (LFV) can naturally appear. We study the physics potential of an electron-photon collider on searching LFV processes e - γ → l - φ (l = μ, τ;φ = H,A) where H and A are extra CP even and odd Higgs bosons, respectively, in the minimal supersymmetric standard model and the effective two Higgs doublet model. The production cross section can be significantly large for the maximal allowed values of the LFV coupling constants under the current experimental data. Present experimental upper bounds on the effective LFV coupling constants would be considerably improved by searching these processes, which would be better than MEG and COMET experiments and also those at LHCb and SuperKEKB. Moreover, one can separately measure chirality of effective LFV coupling constants via these processes by selecting electron polarizations. (author)

A Search for Neutral Supersymmetric Higgs Bosons at D0

International Nuclear Information System (INIS)

Osman, Nicolas Ahmed

2010-01-01

A search for Higgs bosons in multijet data from the D0 detector is reported in this thesis. The Higgs boson is the only remaining undiscovered particle in the Standard Model of particle physics, and plays an integral role in this model. It is known that this model is not a complete description of fundamental physics (it does not describe gravity, for example), and so searches for physics beyond the Standard Model are an important part of particle physics. One extension of the Standard Model, the Minimal Supersymmetric Standard Model (MSSM), predicts the existence of five Higgs bosons, two of which can show an enhanced coupling to bottom quarks. For this reason, a search in the bbb (multijet) channel is a sensitive test of Higgs boson physics. The analysis described in this thesis was conducted over 6.6 fb -1 of data. At the time of writing, the best limits on tan β (a key parameter of the MSSM) in the multijet channel were set by D0. The new analysis described in this thesis included more data than the previous analysis in the channel, and made use of a new trigger and event-based analysis method. An improved Multivariate Analysis technique was used to separate signal and background events and produce a final discriminant for the limit setting process. These changes increased the expected sensitivity of this measurement by roughly 50% more than would be expected from the increase in the size of data sample alone.

Swimming against the tide: explaining the Higgs

CERN Multimedia

Emma Sanders

2012-01-01

"Never before in the field of science journalism have so few journalists understood what so many physicists were telling them!" tweeted the UK Channel 4’s Tom Clarke from last December’s Higgs seminar. As a consequence, most coverage focused on debates over the use of the label “god particle” and the level of excitement of the physicists (high), whilst glossing over what this excitement was actually all about.   So what is the Higgs? Something fundamental. Something to do with mass. If your interest in physics is more than simply passing, you may find that rooms full of chattering politicians or the use of different footwear when walking through snow just don’t do the job in convincing you why the Higgs is so important. And if images of fish make you feel like a fish out of water - or at least one swimming against a strong current - then perhaps you would appreciate a different approach. The need for the Higgs Whilst gauge th...

Higgs bosons in extra dimensions

Science.gov (United States)

Quiros, Mariano

2015-05-01

In this paper, motivated by the recent discovery of a Higgs-like boson at the Large Hadron Collider (LHC) with a mass mH≃125 GeV, we review different models where the hierarchy problem is solved by means of a warped extra dimension. In the Randall-Sundrum (RS) model electroweak observables provide very strong bounds on the mass of KK modes which motivates extensions to overcome this problem. Two extensions are briefly discussed. One particular extension is based on the deformation of the metric such that it strongly departs from the AdS5 structure in the IR region while it goes asymptotically to AdS5 in the UV brane. This model has the IR brane close to a naked metric singularity (which is outside the physical interval) characteristic of soft-walls constructions. The proximity of the singularity provides a strong wave function renormalization for the Higgs field which suppresses the T and S parameters. The second class of considered extensions are based on the introduction of an extra gauge group in the bulk such that the custodial SU(2)R symmetry is gauged and protects the T parameter. By further enlarging the bulk gauge symmetry one can find models where the Higgs is identified with the fifth component of gauge fields and for which the Higgs potential along with the Higgs mass can be dynamically determined by the Coleman-Weinberg mechanism.

Higgs pair production: choosing benchmarks with cluster analysis

Energy Technology Data Exchange (ETDEWEB)

Carvalho, Alexandra; Dall’Osso, Martino; Dorigo, Tommaso [Dipartimento di Fisica e Astronomia and INFN, Sezione di Padova,Via Marzolo 8, I-35131 Padova (Italy); Goertz, Florian [CERN,1211 Geneva 23 (Switzerland); Gottardo, Carlo A. [Physikalisches Institut, Universität Bonn,Nussallee 12, 53115 Bonn (Germany); Tosi, Mia [CERN,1211 Geneva 23 (Switzerland)

2016-04-20

New physics theories often depend on a large number of free parameters. The phenomenology they predict for fundamental physics processes is in some cases drastically affected by the precise value of those free parameters, while in other cases is left basically invariant at the level of detail experimentally accessible. When designing a strategy for the analysis of experimental data in the search for a signal predicted by a new physics model, it appears advantageous to categorize the parameter space describing the model according to the corresponding kinematical features of the final state. A multi-dimensional test statistic can be used to gauge the degree of similarity in the kinematics predicted by different models; a clustering algorithm using that metric may allow the division of the space into homogeneous regions, each of which can be successfully represented by a benchmark point. Searches targeting those benchmarks are then guaranteed to be sensitive to a large area of the parameter space. In this document we show a practical implementation of the above strategy for the study of non-resonant production of Higgs boson pairs in the context of extensions of the standard model with anomalous couplings of the Higgs bosons. A non-standard value of those couplings may significantly enhance the Higgs boson pair-production cross section, such that the process could be detectable with the data that the LHC will collect in Run 2.

Molasses or Crowds: Making Sense of the Higgs Boson with Two Popular Analogies

Science.gov (United States)

Alsop, S.; Beale, S.

2013-01-01

The recent discovery of the Higgs boson at the Large Hadron Collider (LHC) has contributed to a surge of interest in particle physics and science education in general. Given the conceptual difficulty of the phenomenon in question, it is inevitable that teachers and science communicators rely on analogies to explain the Higgs physics and its…

Higgs potential in the type II seesaw model

International Nuclear Information System (INIS)

Arhrib, A.; Benbrik, R.; Chabab, M.; Rahili, L.; Ramadan, J.; Moultaka, G.; Peyranere, M. C.

2011-01-01

The standard model Higgs sector, extended by one weak gauge triplet of scalar fields with a very small vacuum expectation value, is a very promising setting to account for neutrino masses through the so-called type II seesaw mechanism. In this paper we consider the general renormalizable doublet/triplet Higgs potential of this model. We perform a detailed study of its main dynamical features that depend on five dimensionless couplings and two mass parameters after spontaneous symmetry breaking, and highlight the implications for the Higgs phenomenology. In particular, we determine (i) the complete set of tree-level unitarity constraints on the couplings of the potential and (ii) the exact tree-level boundedness from below constraints on these couplings, valid for all directions. When combined, these constraints delineate precisely the theoretically allowed parameter space domain within our perturbative approximation. Among the seven physical Higgs states of this model, the mass of the lighter (heavier) CP even state h 0 (H 0 ) will always satisfy a theoretical upper (lower) bound that is reached for a critical value μ c of μ (the mass parameter controlling triple couplings among the doublet/triplet Higgses). Saturating the unitarity bounds, we find an upper bound m h 0 or approx. μ c and μ c . In the first regime the Higgs sector is typically very heavy, and only h 0 that becomes SM-like could be accessible to the LHC. In contrast, in the second regime, somewhat overlooked in the literature, most of the Higgs sector is light. In particular, the heaviest state H 0 becomes SM-like, the lighter states being the CP odd Higgs, the (doubly) charged Higgses, and a decoupled h 0 , possibly leading to a distinctive phenomenology at the colliders.

ILC Higgs White Paper

CERN Document Server

Asner, D.M.; Calancha, C.; Fujii, K.; Graf, N.; Haber, H.E.; Ishikawa, A.; Kanemura, S.; Kawada, S.; Kurata, M.; Miyamoto, A.; Neal, H.; Ono, H.; Potter, C.; Strube, J.; Suehara, T.; Tanabe, T.; Tian, J.; Tsumura, J.; Watanuki, S.; Weiglein, G.; Yagyu, K.; Yokoya, H.

2013-01-01

The ILC Higgs White Paper is a review of Higgs Boson theory and experiment at the International Linear Collider (ILC). Theory topics include the Standard Model Higgs, the two-Higgs doublet model, alternative approaches to electroweak symmetry breaking, and precision goals for Higgs boson experiments. Experimental topics include the measurement of the Higgs cross section times branching ratio for various Higgs decay modes at ILC center of mass energies of 250, 500, and 1000 GeV, and the extraction of Higgs couplings and the total Higgs width from these measurements. Luminosity scenarios based on the ILC TDR machine design are used throughout. The gamma-gamma collider option at the ILC is also discussed.

Direct and indirect signals of natural composite Higgs models

Science.gov (United States)

Niehoff, Christoph; Stangl, Peter; Straub, David M.

2016-01-01

We present a comprehensive numerical analysis of a four-dimensional model with the Higgs as a composite pseudo-Nambu-Goldstone boson that features a calculable Higgs potential and protective custodial and flavour symmetries to reduce electroweak fine-tuning. We employ a novel numerical technique that allows us for the first time to study constraints from radiative electroweak symmetry breaking, Higgs physics, electroweak precision tests, flavour physics, and direct LHC bounds on fermion and vector boson resonances in a single framework. We consider four different flavour symmetries in the composite sector, one of which we show to not be viable anymore in view of strong precision constraints. In the other cases, all constraints can be passed with a sub-percent electroweak fine-tuning. The models can explain the excesses recently observed in WW, WZ, Wh and ℓ + ℓ - resonance searches by ATLAS and CMS and the anomalies in angular observables and branching ratios of rare semi-leptonic B decays observed by LHCb. Solving the B physics anomalies predicts the presence of a dijet or toverline{t} resonance around 1 TeV just below the sensitivity of LHC run 1. We discuss the prospects to probe the models at run 2 of the LHC. As a side product, we identify several gaps in the searches for vector-like quarks at hadron colliders, that could be closed by reanalyzing existing LHC data.

Analysis of the phase structure in extended Higgs models

Energy Technology Data Exchange (ETDEWEB)

Seniuch, M.

2006-07-07

We study the generation of the baryon asymmetry in the context of electroweak baryogenesis in two different extensions of the Standard Model. First, we consider an effective theory, in which the Standard Model is augmented by an additional dimension-six Higgs operator. The effects of new physics beyond a cut-off scale are parameterized by this operator. The second model is the two-Higgs-doublet model, whose particle spectrum is extended by two further neutral and two charged heavy Higgs bosons. In both cases we focus on the properties of the electroweak phase transition, especially on its strength and the profile of the nucleating bubbles. After reviewing some general aspects of the electroweak phase transition and baryogenesis we derive the respective thermal effective potentials to one-loop order. We systematically study the parameter spaces, using numerical methods, and compute the strength of the phase transition and the wall thickness as a function of the Higgs masses. We find a strong first order transition for a light Higgs state with a mass up to about 200 GeV. In case of the dimension-six model the cut-off scale has to stay between 500 and 850 GeV, in the two-Higgs-doublet model one needs at least one heavy Higgs mass of 300 GeV. The wall thickness varies for both theories in the range roughly from two to fifteen, in units of the inverse critical temperature. We also estimate the size of the electron and neutron electric dipole moments, since new sources of CP violation give rise to them. In wide ranges of the parameter space we are not in conflict with the experimental bounds. Finally the baryon asymmetry, which is predicted by these models, is related to the Higgs mass and the other appropriate input parameters. In both models the measured baryon asymmetry can be achieved for natural values of the model parameters. (orig.)

Postinflationary Higgs relaxation and the origin of matter-antimatter asymmetry.

Science.gov (United States)

Kusenko, Alexander; Pearce, Lauren; Yang, Louis

2015-02-13

The recent measurement of the Higgs boson mass implies a relatively slow rise of the standard model Higgs potential at large scales, and a possible second minimum at even larger scales. Consequently, the Higgs field may develop a large vacuum expectation value during inflation. The relaxation of the Higgs field from its large postinflationary value to the minimum of the effective potential represents an important stage in the evolution of the Universe. During this epoch, the time-dependent Higgs condensate can create an effective chemical potential for the lepton number, leading to a generation of the lepton asymmetry in the presence of some large right-handed Majorana neutrino masses. The electroweak sphalerons redistribute this asymmetry between leptons and baryons. This Higgs relaxation leptogenesis can explain the observed matter-antimatter asymmetry of the Universe even if the standard model is valid up to the scale of inflation, and any new physics is suppressed by that high scale.

Exploring extended scalar sectors with di-Higgs signals: a Higgs EFT perspective

Science.gov (United States)

Corbett, Tyler; Joglekar, Aniket; Li, Hao-Lin; Yu, Jiang-Hao

2018-05-01

We consider extended scalar sectors of the Standard Model as ultraviolet complete motivations for studying the effective Higgs self-interaction operators of the Standard Model effective field theory. We investigate all motivated heavy scalar models which generate the dimension-six effective operator, | H|6, at tree level and proceed to identify the full set of tree-level dimension-six operators by integrating out the heavy scalars. Of seven models which generate | H|6 at tree level only two, quadruplets of hypercharge Y = 3 Y H and Y = Y H , generate only this operator. Next we perform global fits to constrain relevant Wilson coefficients from the LHC single Higgs measurements as well as the electroweak oblique parameters S and T. We find that the T parameter puts very strong constraints on the Wilson coefficient of the | H|6 operator in the triplet and quadruplet models, while the singlet and doublet models could still have Higgs self-couplings which deviate significantly from the standard model prediction. To determine the extent to which the | H|6 operator could be constrained, we study the di-Higgs signatures at the future 100 TeV collider and explore future sensitivity of this operator. Projected onto the Higgs potential parameters of the extended scalar sectors, with 30 ab-1 luminosity data we will be able to explore the Higgs potential parameters in all seven models.

A study of the Higgs boson decay $H\\rightarrow ZZ^{(*)}\\rightarrow4 \\ell$ and inner detector performance studies with the ATLAS experiment

CERN Document Server

Selbach, Karoline Elfriede

The Higgs mechanism is the last piece of the SM to be discovered which is responsible for giving mass to the electroweak $W^{\\pm}$ and $Z$ bosons. Experimental evidence for the Higgs boson is therefore important and is currently explored at the Large Hadron Collider (LHC) at CERN. The ATLAS experiment (A Toroidal LHC ApparatuS) is analysing a wide range of physics processes from collisions produced by the LHC at a centre-of-mass energy of 7-8$\\,$TeV and a peak luminosity of $7.73\\times10^{33}\\,\\mathrm{cm^{-2}s^{-1}}$. This thesis concentrates on the discovery and mass measurement of the Higgs boson. The analysis using the $H\\rightarrow ZZ^{(*)}\\rightarrow4 \\ell$ channel is presented, where $\\ell$ denotes electrons or muons. Statistical methods with non-parametric models are successfully cross-checked with parametric models. The per-event errors studied to improve the mass determination decreases the total mass uncertainty by $9\\%$. The other main focus is the performance of the initial, and possible upgraded...

Mooses, topology and Higgs

International Nuclear Information System (INIS)

Gregoire, Thomas; Wacker, Jay G.

2002-01-01

New theories of electroweak symmetry breaking have recently been constructed that stabilize the weak scale and do not rely upon supersymmetry. In these theories the Higgs boson is a weakly coupled pseudo-Goldstone boson. In this note we study the class of theories that can be described by theory spaces and show that the fundamental group of theory space describes all the relevant classical physics in the low energy theory. The relationship between the low energy physics and the topological properties of theory space allow a systematic method for constructing theory spaces that give any desired low energy particle content and potential. This provides us with tools for analyzing and constructing new theories of electroweak symmetry breaking. (author)

Conformally invariant Inert Higgs doublet model: an unified model for Inflation and Dark matter

International Nuclear Information System (INIS)

Das, Moumita; Mohanty, Subhendra

2012-01-01

Motivation of our present study is the searching for an unified model which can describe both the inflation as well as dark matter. From particle physics point of view, Higgs can be the most interesting candidate for the scalar field inflation. Conformal coupling of the inflaton with the gravity can generate the density perturbation and we use this idea in a realistic inert Higgs doublet model. We study the loop corrections of this conformally coupled system and in present era there is electroweak symmetry breaking to provide the mass of the particles. Study of the mass spectrum in present era reveals the scalar dark matter with mass 33.7 GeV and lightest Higgs at 125.6 GeV.

Three-body decays of Higgs bosons at LEP2 and application to a hidden fermiophobic Higgs

International Nuclear Information System (INIS)

Akeroyd, A.G.

1999-01-01

We study the decays of Higgs bosons to a lighter Higgs boson and a virtual gauge boson in the context of the non-supersymmetric two-Higgs doublet model (2HDM). We consider the phenomenological impact at LEP2 and find that such decays, when open, may be dominant in regions of parameter space and thus affect current Higgs boson search techniques. Three-body decays would be a way of producing light neutral Higgs bosons which have so far escaped detection at LEP due to suppressed couplings to the Z, and are of particular importance in the 2HDM (Model I) which allows both a light fermiophobic Higgs and a light charged scalar

The supersymmetric Higgs pseudoscalar and its production in toponium decay

International Nuclear Information System (INIS)

Gamberini, G.; Giudice, G.F.; Ridolfi, G.

1987-01-01

In the minimal supersymmetric extension of the standard model one scalar Higgs boson is forced to be lighter than the Z 0 . We consider here the bounds, imposed by supersymmetry, on the mass of the physical Higgs pseudoscalar. It turns out that, although fairly stringent limits are found, it is still conveivable that this particle is light enough to be discovered at SLC and LEP. Its production rate in toponium decay is computed and discussed in view of the bounds on the supersymmetric Higgs sector parameters. (orig.)

Doubling Up on Supersymmetry in the Higgs Sector

CERN Document Server

Ellis, John; Sanz, Verónica

2016-10-17

We explore the possibility that physics at the TeV scale possesses approximate $N = 2$ supersymmetry, which is reduced to the $N=1$ minimal supersymmetric extension of the Standard Model (MSSM) at the electroweak scale. This doubling of supersymmetry modifies the Higgs sector of the theory, with consequences for the masses, mixings and couplings of the MSSM Higgs bosons, whose phenomenological consequences we explore in this paper. The mass of the lightest neutral Higgs boson $h$ is independent of $\\tan \\beta$ at the tree level, and the decoupling limit is realized whatever the values of the heavy Higgs boson masses. Radiative corrections to the top quark and stop squarks dominate over those due to particles in $N=2$ gauge multiplets. We assume that these radiative corrections fix $m_h \\simeq 125$ GeV, whatever the masses of the other neutral Higgs bosons $H, A$, a scenario that we term the $h$2MSSM. Since the $H, A$ bosons decouple from the $W$ and $Z$ bosons in the $h$2MSSM at tree level, only the LHC const...

Higgs CAT

Energy Technology Data Exchange (ETDEWEB)

Passarino, Giampiero [Universita di Torino, Dipartimento di Fisica Teorica, Turin (Italy); INFN, Sezione di Torino, Turin (Italy)

2014-05-15

Higgs Computed Axial Tomography, an excerpt. The Higgs boson lineshape (..and the devil hath power to assume a pleasing shape, Hamlet, Act II, scene 2) is analyzed for the gg → ZZ process, with special emphasis on the off-shell tail which shows up for large values of the Higgs virtuality. The effect of including background and interference is also discussed. The main focus of this work is on residual theoretical uncertainties, discussing how much-improved constraint on the Higgs intrinsic width can be revealed by an improved approach to analysis. (orig.)

Higgs CAT

International Nuclear Information System (INIS)

Passarino, Giampiero

2014-01-01

Higgs Computed Axial Tomography, an excerpt. The Higgs boson lineshape (..and the devil hath power to assume a pleasing shape, Hamlet, Act II, scene 2) is analyzed for the gg → ZZ process, with special emphasis on the off-shell tail which shows up for large values of the Higgs virtuality. The effect of including background and interference is also discussed. The main focus of this work is on residual theoretical uncertainties, discussing how much-improved constraint on the Higgs intrinsic width can be revealed by an improved approach to analysis. (orig.)

“Electroweak symmetry breaking: to Higgs or not to Higgs” (3/3)

CERN Multimedia

CERN. Geneva

2009-01-01

How do elementary particles acquire their mass? What is making the photon different from the Z boson? In a word: How is electroweak symmetry broken? This is one of the pressing questions in particle physics that the LHC will answer soon. The aim of this lectures is, after briefly introducing SM physics and the conventional Higgs mechanism, to give a survey of recent attempts to go beyond a simple elementary Higgs. In particular, I will describe composite models (where the Higgs boson emerges from a strongly-interacting sector) and Higsless models. Distinctive signatures at the LHC are expected and will reveal the true nature of the electroweak symmetry sector.

“Electroweak symmetry breaking: to Higgs or not to Higgs” (2/3)

CERN Multimedia

CERN. Geneva

2009-01-01

How do elementary particles acquire their mass? What is making the photon different from the Z boson? In a word: How is electroweak symmetry broken? This is one of the pressing questions in particle physics that the LHC will answer soon. The aim of this lectures is, after briefly introducing SM physics and the conventional Higgs mechanism, to give a survey of recent attempts to go beyond a simple elementary Higgs. In particular, I will describe composite models (where the Higgs boson emerges from a strongly-interacting sector) and Higsless models. Distinctive signatures at the LHC are expected and will reveal the true nature of the electroweak symmetry sector.

“Electroweak symmetry breaking: to Higgs or not to Higgs” (1/3)

CERN Multimedia

CERN. Geneva

2009-01-01

How do elementary particles acquire their mass? What is making the photon different from the Z boson? In a word: How is electroweak symmetry broken? This is one of the pressing questions in particle physics that the LHC will answer soon. The aim of this lectures is, after briefly introducing SM physics and the conventional Higgs mechanism, to give a survey of recent attempts to go beyond a simple elementary Higgs. In particular, I will describe composite models (where the Higgs boson emerges from a strongly-interacting sector) and Higsless models. Distinctive signatures at the LHC are expected and will reveal the true nature of the electroweak symmetry sector.

THE HIGGS WORKING GROUP: SUMMARY REPORT.

Energy Technology Data Exchange (ETDEWEB)

DAWSON, S.; ET AL.

2005-08-01

This working group has investigated Higgs boson searches at the Tevatron and the LHC. Once Higgs bosons are found their properties have to be determined. The prospects of Higgs coupling measurements at the LHC and a high-energy linear e{sup +}e{sup -} collider are discussed in detail within the Standard Model and its minimal supersymmetric extension (MSSM). Recent improvements in the theoretical knowledge of the signal and background processes are presented and taken into account. The residual uncertainties are analyzed in detail. Theoretical progress is discussed in particular for the gluon-fusion processes gg {yields} H(+j), Higgs-bremsstrahlung off bottom quarks and the weak vector-boson-fusion (VBF) processes. Following the list of open questions of the last Les Houches workshop in 2001 several background processes have been calculated at next-to-leading order, resulting in a significant reduction of the theoretical uncertainties. Further improvements have been achieved for the Higgs sectors of the MSSM and NMSSM. This report summarizes our work performed before and after the workshop in Les Houches. Part A describes the theoretical developments for signal and background processes. Part B presents recent progress in Higgs boson searches at the Tevatron collider. Part C addresses the determination of Higgs boson couplings, part D the measurement of tan {beta} and part E Higgs boson searches in the VBF processes at the LHC. Part F summarizes Higgs searches in supersymmetric Higgs decays, part G photonic Higgs decays in Higgs-strahlung processes at the LHC, while part H concentrates on MSSM Higgs bosons in the intense-coupling regime at the LHC. Part I presents progress in charged Higgs studies and part J the Higgs discovery potential in the NMSSM at the LHC. The last part K describes Higgs coupling measurements at a 1 TeV linear e{sup +}e{sup -} collider.

THE HIGGS WORKING GROUP: SUMMARY REPORT

International Nuclear Information System (INIS)

DAWSON, S.

2005-01-01

This working group has investigated Higgs boson searches at the Tevatron and the LHC. Once Higgs bosons are found their properties have to be determined. The prospects of Higgs coupling measurements at the LHC and a high-energy linear e + e - collider are discussed in detail within the Standard Model and its minimal supersymmetric extension (MSSM). Recent improvements in the theoretical knowledge of the signal and background processes are presented and taken into account. The residual uncertainties are analyzed in detail. Theoretical progress is discussed in particular for the gluon-fusion processes gg → H(+j), Higgs-bremsstrahlung off bottom quarks and the weak vector-boson-fusion (VBF) processes. Following the list of open questions of the last Les Houches workshop in 2001 several background processes have been calculated at next-to-leading order, resulting in a significant reduction of the theoretical uncertainties. Further improvements have been achieved for the Higgs sectors of the MSSM and NMSSM. This report summarizes our work performed before and after the workshop in Les Houches. Part A describes the theoretical developments for signal and background processes. Part B presents recent progress in Higgs boson searches at the Tevatron collider. Part C addresses the determination of Higgs boson couplings, part D the measurement of tan β and part E Higgs boson searches in the VBF processes at the LHC. Part F summarizes Higgs searches in supersymmetric Higgs decays, part G photonic Higgs decays in Higgs-strahlung processes at the LHC, while part H concentrates on MSSM Higgs bosons in the intense-coupling regime at the LHC. Part I presents progress in charged Higgs studies and part J the Higgs discovery potential in the NMSSM at the LHC. The last part K describes Higgs coupling measurements at a 1 TeV linear e + e - collider

Penguin effects induced by the two-Higgs-doublet model and charmless B-meson decays

International Nuclear Information System (INIS)

Davies, A.J.; Joshi, G.C.; Matsuda, M.

1991-03-01

Nonstandard physical effects through the penguin diagram induced by the charged Higgs scalar contribution in the two-Higgs-doublet model are analysed. The non-leptonic β-decay processes including the non-standard two-Higgs-doublet contribution are compared with the standard model results, which arise from the magnetic gluon transition term. The charged Higgs contribution gives a sizable enhancement to the branching fractions of β-meson charmless decay. 13 refs., 4 figs

HiggsSignals. Confronting arbitrary Higgs sectors with measurements at the Tevatron and the LHC

Energy Technology Data Exchange (ETDEWEB)

Bechtle, Philip [Bonn Univ. (Germany). Physikalisches Inst.; Heinemeyer, Sven [Instituto de Fisica de Cantabria (CSIC-UC), Santander (Spain); Staal, Oscar [Stockholm Univ. (Sweden). The Oskar Klein Centre; Stefaniak, Tim [Bonn Univ. (Germany). Physikalisches Inst.; Bonn Univ. (Germany). Bethe Center for Theoretical Physics; Weiglein, Georg [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2013-05-15

HiggsSignals is a Fortran90 computer code that allows to test the compatibility of Higgs sector predictions against Higgs rates and masses measured at the LHC or the Tevatron. Arbitrary models with any number of Higgs bosons can be investigated using a model-independent input scheme based on HiggsBounds. The test is based on the calculation of a {chi}{sup 2} measure from the predictions and the measured Higgs rates and masses, with the ability of fully taking into account systematics and correlations for the signal rate predictions, luminosity and Higgs mass predictions. It features two complementary methods for the test. First, the peak-centered method, in which each observable is defined by a Higgs signal rate measured at a specific hypothetical Higgs mass, corresponding to a tentative Higgs signal. Second, the mass-centered method, where the test is evaluated by comparing the signal rate measurement to the theory prediction at the Higgs mass predicted by the model. The program allows for the simultaneous use of both methods, which is useful in testing models with multiple Higgs bosons. The code automatically combines the signal rates of multiple Higgs bosons if their signals cannot be resolved by the experimental analysis. We compare results obtained with HiggsSignals to official ATLAS and CMS results for various examples of Higgs property determinations and find very good agreement. A few examples of HiggsSignals applications are provided, going beyond the scenarios investigated by the LHC collaborations. For models with more than one Higgs boson we recommend to use HiggsSignals and HiggsBounds in parallel to exploit the full constraining power of Higgs search exclusion limits and the measurements of the signal seen at m{sub H} {approx} 125.5 GeV.

Building and testing models with extended Higgs sectors

Science.gov (United States)

Ivanov, Igor P.

2017-07-01

Models with non-minimal Higgs sectors represent a mainstream direction in theoretical exploration of physics opportunities beyond the Standard Model. Extended scalar sectors help alleviate difficulties of the Standard Model and lead to a rich spectrum of characteristic collider signatures and astroparticle consequences. In this review, we introduce the reader to the world of extended Higgs sectors. Not pretending to exhaustively cover the entire body of literature, we walk through a selection of the most popular examples: the two- and multi-Higgs-doublet models, as well as singlet and triplet extensions. We will show how one typically builds models with extended Higgs sectors, describe the main goals and the challenges which arise on the way, and mention some methods to overcome them. We will also describe how such models can be tested, what are the key observables one focuses on, and illustrate the general strategy with a subjective selection of results.

Phenomenology of Higgs particles

International Nuclear Information System (INIS)

Jarlskog, C.; Stockholm Univ.

1985-01-01

These lecture notes are organized as follows: 1. Introduction, 2. Interactions and decay modes of the Standard Higgs phisub(O), 3. Nonstandard Higgs multiplets, 4. Upper limits on the Higgs mass, 5. Lower limits on the Higgs mass, 6. Production mechanisms for the Standard Higgs, 7. Outlook. (orig.)

Partially composite Higgs models

DEFF Research Database (Denmark)

Alanne, Tommi; Buarque Franzosi, Diogo; Frandsen, Mads T.

2018-01-01

We study the phenomenology of partially composite-Higgs models where electroweak symmetry breaking is dynamically induced, and the Higgs is a mixture of a composite and an elementary state. The models considered have explicit realizations in terms of gauge-Yukawa theories with new strongly...... interacting fermions coupled to elementary scalars and allow for a very SM-like Higgs state. We study constraints on their parameter spaces from vacuum stability and perturbativity as well as from LHC results and find that requiring vacuum stability up to the compositeness scale already imposes relevant...... constraints. A small part of parameter space around the classically conformal limit is stable up to the Planck scale. This is however already strongly disfavored by LHC results. in different limits, the models realize both (partially) composite-Higgs and (bosonic) technicolor models and a dynamical extension...

Professor Peter Higgs: "My Life as a Boson"

CERN Multimedia

CERN. Geneva

2012-01-01

Professor Peter Higgs played a key role in the development of the Standard Model, our current theory of fundamental physics. The search for the Higgs Boson is the centrepiece of the LHC programme at CERN, and the existence of this famously elusive particle is likely to be confirmed or refuted with data currently being collected, using apparatus partly designed at Bristol. Professor Higgs will introduce the ideas of spontaneous symmetry breaking, and discuss how these developed from their application in condensed matter through the earlier work of Yoichiro Nambu and Jeffrey Goldstone, to the work of Robert Brout, Francois Englert and himself in 1964. The subsequent application of these ideas to electroweak theory will be discussed briefly.

Search for Heavy Higgs Bosons with the ATLAS Detector

CERN Document Server

Schaarschmidt, Jana; The ATLAS collaboration

2018-01-01

ATLAS performed searches for heavy Higgs bosons, whose presence would establish the existance of new physics. Searches for charged and neutral Higgs bosons are carried out using 8 or 13 TeV data for various production modes and in many different final states. The searches all yield null results. Exclusions limits are set on the production cross section and on parameters in various benchmark models.

Cosmological implications of Higgs near-criticality.

Science.gov (United States)

Espinosa, J R

2018-03-06

The Standard Model electroweak (EW) vacuum, in the absence of new physics below the Planck scale, lies very close to the boundary between stability and metastability, with the last option being the most probable. Several cosmological implications of this so-called 'near-criticality' are discussed. In the metastable vacuum case, the main challenges that the survival of the EW vacuum faces during the evolution of the Universe are analysed. In the stable vacuum case, the possibility of implementing Higgs inflation is critically examined.This article is part of the Theo Murphy meeting issue 'Higgs cosmology'. © 2018 The Author(s).

Higgs boson phenomenology at the LHC

International Nuclear Information System (INIS)

Kirchner, Sebastian

2016-01-01

The outstanding performance of the Large Hadron Collider (LHC) led to the discovery of the Higgs boson in 2012. The paramount endeavour after this discovery is the examination of the Higgs-boson properties, amongst others the determination of its CP quantum number and total decay width. The experimental analysis of both properties requires precise theoretical input within the Standard Model of particle physics. Theoretical methods and predictions at next-to-leading-order (NLO) in perturbative Quantum Chromodynamics (QCD), addressing the CP nature and decay width of the Higgs boson, are presented in this thesis. The thesis is split in two parts: The first part addresses the Caola-Melnikov method, which is utilised to constrain the Higgs width that is experimentally not directly measurable. The method relies on cross section measurements on and far off the Higgs boson peak. Two-loop corrections via a heavy top quark to the gluon-gluon initialised Z boson pair-production are examined as an expansion about the heavy-top limit combined with a conformal mapping and Pade approximants. The impact of the full NLO QCD corrections to the signal and background cross sections, relevant for bounding the Higgs width, is investigated. The second part of this thesis examines how precisely the CP nature of the Higgs boson can be unravelled in its decay to tau lepton pairs. All subsequent major charged-prong decays of the tau leptons are included.The impact parameter method is utilised and allows to extract the CP-mixing angle of the Higgs boson from the distribution of a signed angle. NLO QCD predictions for the signal process as well as the Drell-Yan background, including a Monte Carlo simulation of measurement uncertainties, are computed. Energy and angular correlations of the charged prongs are analysed and used to suppress the Drell-Yan background contribution. In a second step, the sensitivity to the CP-mixing angle is increased by combining the impact parameter method with the

RG running in a minimal UED model in light of recent LHC Higgs mass bounds

International Nuclear Information System (INIS)

Blennow, Mattias; Melbéus, Henrik; Ohlsson, Tommy; Zhang, He

2012-01-01

We study how the recent ATLAS and CMS Higgs mass bounds affect the renormalization group running of the physical parameters in universal extra dimensions. Using the running of the Higgs self-coupling constant, we derive bounds on the cutoff scale of the extra-dimensional theory itself. We show that the running of physical parameters, such as the fermion masses and the CKM mixing matrix, is significantly restricted by these bounds. In particular, we find that the running of the gauge couplings cannot be sufficient to allow gauge unification at the cutoff scale.

Boosting the charged Higgs search prospects using jet substructure at the LHC

Energy Technology Data Exchange (ETDEWEB)

Li, Jinmian [Center of Excellence for Particle Physics at Terascale, University of Adelaide,Adelaide, 5005 South (Australia); School of Physics, Korea Institute for Advanced Study,Seoul, 130-722 (Korea, Republic of); Patrick, Riley; Sharma, Pankaj; Williams, Anthony G. [Center of Excellence for Particle Physics at Terascale, University of Adelaide,Adelaide, 5005 South (Australia)

2016-11-28

Charged Higgs bosons are predicted in variety of theoretically well-motivated new physics models with extended Higgs sectors. In this study, we focus on a type-II two Higgs doublet model (2HDM-II) and consider a heavy charged Higgs with its mass ranging from 500 GeV to 1 TeV as dictated by the b→sγ constraints which render M{sub H{sup ±}}>480 GeV. We study the dominant production mode H{sup ±}t associated production with H{sup ±}→W{sup ±}A being the dominant decay channel when the pseudoscalar A is considerably lighter. For such a heavy charged Higgs, both the decay products W{sup ±} and A are relatively boosted. In such a scenario, we apply the jet substructure analysis of tagging the fat pseudoscalar and W jets in order to eliminate the standard model background efficiently. We perform a detailed detector simulation for the signal and background processes at the 14 TeV LHC. We introduce various kinematical cuts to determine the signal significance for a number of benchmark points with charged Higgs boson mass from 500 GeV to 1 TeV in the W{sup ±}A decay channel. Finally we perform a multivariate analysis utilizing a boosted decision tree algorithm to optimize these significances.

Higgs Stability and the 750 GeV Diphoton Excess

CERN Document Server

Salvio, Alberto

2016-01-01

We study the implications of a possible unstable particle with mass $M_X<$ TeV for the Higgs stability, naturalness and inflation. We pay particular attention to the case $M_X\\approx$ 750 GeV, suggested by recent results of ATLAS and CMS on diphoton final states, and work within the minimal model: we add to the Standard Model field content a pseudoscalar and a vector-like charged quark. This can stabilize the electroweak vacuum without invoking new physics at very high energies, which would give an unnaturally large contribution to the Higgs mass. We also show that inflation can be obtained via a UV modification of General Relativity.

Gauge turbulence, topological defect dynamics, and condensation in Higgs models

Energy Technology Data Exchange (ETDEWEB)

Gasenzer, Thomas [Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, 69120 Heidelberg (Germany); ExtreMe Matter Institute EMMI, GSI, Planckstraße 1, D-64291 Darmstadt (Germany); McLerran, Larry [Physics Department, Bldg. 510A, Brookhaven National Laboratory, Upton, NY 11973 (United States); RIKEN BNL Research Center, Bldg. 510A, Brookhaven National Laboratory, Upton, NY 11973 (United States); Physics Department, China Central Normal University, Wuhan (China); Pawlowski, Jan M.; Sexty, Dénes [Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, 69120 Heidelberg (Germany); ExtreMe Matter Institute EMMI, GSI, Planckstraße 1, D-64291 Darmstadt (Germany)

2014-10-15

The real-time dynamics of topological defects and turbulent configurations of gauge fields for electric and magnetic confinement are studied numerically within a 2+1D Abelian Higgs model. It is shown that confinement is appearing in such systems equilibrating after a strong initial quench such as the overpopulation of the infrared modes. While the final equilibrium state does not support confinement, metastable vortex defect configurations appearing in the gauge field are found to be closely related to the appearance of physically observable confined electric and magnetic charges. These phenomena are seen to be intimately related to the approach of a non-thermal fixed point of the far-from-equilibrium dynamical evolution, signaled by universal scaling in the gauge-invariant correlation function of the Higgs field. Even when the parameters of the Higgs action do not support condensate formation in the vacuum, during this approach, transient Higgs condensation is observed. We discuss implications of these results for the far-from-equilibrium dynamics of Yang–Mills fields and potential mechanisms of how confinement and condensation in non-Abelian gauge fields can be understood in terms of the dynamics of Higgs models. These suggest that there is an interesting new class of dynamics of strong coherent turbulent gauge fields with condensates.

Gauge turbulence, topological defect dynamics, and condensation in Higgs models

International Nuclear Information System (INIS)

Gasenzer, Thomas; McLerran, Larry; Pawlowski, Jan M.; Sexty, Dénes

2014-01-01

The real-time dynamics of topological defects and turbulent configurations of gauge fields for electric and magnetic confinement are studied numerically within a 2+1D Abelian Higgs model. It is shown that confinement is appearing in such systems equilibrating after a strong initial quench such as the overpopulation of the infrared modes. While the final equilibrium state does not support confinement, metastable vortex defect configurations appearing in the gauge field are found to be closely related to the appearance of physically observable confined electric and magnetic charges. These phenomena are seen to be intimately related to the approach of a non-thermal fixed point of the far-from-equilibrium dynamical evolution, signaled by universal scaling in the gauge-invariant correlation function of the Higgs field. Even when the parameters of the Higgs action do not support condensate formation in the vacuum, during this approach, transient Higgs condensation is observed. We discuss implications of these results for the far-from-equilibrium dynamics of Yang–Mills fields and potential mechanisms of how confinement and condensation in non-Abelian gauge fields can be understood in terms of the dynamics of Higgs models. These suggest that there is an interesting new class of dynamics of strong coherent turbulent gauge fields with condensates

Unitarizing Higgs Inflation

CERN Document Server

Giudice, Gian F

2011-01-01

We consider a simple extension of the Standard Model Higgs inflation with one new real scalar field which preserves unitarity up to the Planck scale. The new scalar field (called sigma) completes in the ultraviolet the theory of Higgs inflation by linearizing the Higgs kinetic term in the Einstein frame, just as the non-linear sigma model is unitarized into its linear version. The unitarity cutoff of the effective theory, obtained by integrating out the sigma field, varies with the background value of the Higgs field. In our setup, both the Higgs field and the sigma field participate in the inflationary dynamics, following the flat direction of the potential. We obtain the same slow-roll parameters and spectral index as in the original Higgs inflation but we find that the Hubble rate during inflation depends not only on the Higgs self-coupling, but also on the unknown couplings of the sigma field.

Unitarizing Higgs inflation

International Nuclear Information System (INIS)

Giudice, Gian F.; Lee, Hyun Min

2011-01-01

We consider a simple extension of the Standard Model Higgs inflation with one new real scalar field which preserves unitarity up to the Planck scale. The new scalar field (called sigma) completes in the ultraviolet the theory of Higgs inflation by linearizing the Higgs kinetic term in the Einstein frame, just as the non-linear sigma model is unitarized into its linear version. The unitarity cutoff of the effective theory, obtained by integrating out the sigma field, varies with the background value of the Higgs field. In our setup, both the Higgs field and the sigma field participate in the inflationary dynamics, following the flat direction of the potential. We obtain the same slow-roll parameters and spectral index as in the original Higgs inflation but we find that the Hubble rate during inflation depends not only on the Higgs self-coupling, but also on the unknown couplings of the sigma field.

Higgs Boson fermionic production and decay modes with the ATLAS detector

CERN Document Server

Piacquadio, Giacinto; The ATLAS collaboration

2018-01-01

The Higgs couplings to heavy quarks, top and bottom quarks, are difficult to directly access experimentally, nevertheless their measurement is crucial for a full characterization of the Higgs sector and to probe a large variety of physics scenarios beyond the Standard Model. In this talk I will discuss the results recently obtained by the ATLAS Collaboration based on Run-2 2015 and 2016 data, which led to evidence for Higgs boson decays to b-quarks and for the ttH production mode.

125 GeV Higgs boson mass from 5D gauge-Higgs unification

Science.gov (United States)

Carson, Jason; Okada, Nobuchika

2018-03-01

In the context of a simple gauge-Higgs unification (GHU) scenario based on the gauge group SU(3)×U(1)^' in a 5D flat space-time, we investigate the possibility of reproducing the observed Higgs boson mass of around 125 GeV. We introduce bulk fermion multiplets with a bulk mass and a (half-)periodic boundary condition. In our analysis, we adopt a low-energy effective theoretical approach of the GHU scenario, where the running Higgs quartic coupling is required to vanish at the compactification scale. Under this "gauge-Higgs condition," we investigate the renormalization group evolution of the Higgs quartic coupling and find a relation between the bulk mass and the compactification scale so as to reproduce the 125 GeV Higgs boson mass. Through quantum corrections at the one-loop level, the bulk fermions contribute to the Higgs boson production and decay processes and deviate the Higgs boson signal strengths at the Large Hadron Collider experiments from the Standard Model (SM) predictions. Employing the current experimental data that show that the Higgs boson signal strengths for a variety of Higgs decay modes are consistent with the SM predictions, we obtain lower mass bounds on the lightest mode of the bulk fermions to be around 1 TeV.

Higgs boson decays and production via gluon fusion at LHC in littlest Higgs models with T parity

International Nuclear Information System (INIS)

Wang Lei; Yang Jinmin

2009-01-01

We study the Higgs boson decays and production via gluon fusion at the LHC as a probe of two typical littlest Higgs models which introduce a top quark partner with different (even and odd) T parity to cancel the Higgs mass quadratic divergence contributed by the top quark. For each model, we consider two different choices for the down-type quark Yukawa couplings. We first examine the branching ratios of the Higgs boson decays and then study the production via gluon fusion followed by the decay into two photons or two weak gauge bosons. We find that the predictions can be quite different for different models or different choices of down-type quark Yukawa couplings, and all these predictions can sizably deviate from the standard model predictions. So the Higgs boson processes at the LHC can be a sensitive probe for these littlest Higgs models.

Higgs physics at future colliders: Recent theoretical developments

Indian Academy of Sciences (India)

is relatively light and if enough integrated luminosity is collected [2,3] and can be detected at the LHC [3,4] over its entire mass range 114.4 GeV <. ~ MА < .... In the MssM, two doublets of Higgs fields are needed to break the electroweak .... BRs of O(10-3) (however, they lead to clear signals and are interesting, since they.

Search for Charged Higgs Bosons with the ATLAS Detector at the LHC

CERN Document Server

Czodrowski, Patrick

2013-07-30

The discovery of a charged Higgs boson, $H^+$, would be an unambiguous evidence for physics beyond the Standard Model. In this thesis a search for the $H^+$, with the ATLAS experiment at the Large Hadron Collider, LHC, at CERN based on data taken in 2011, are described. A re-analysis of the charged Higgs boson search, utilising the ratio-method, was performed, which greatly enhanced the sensitivity compared to the traditional direct search approach. Light charged Higgs bosons, with a mass lower than the top quark mass, can be produced in top quark decays. Due to the large production cross-section of top quark pairs the light charged Higgs bosons are accessible with early LHC data, in contrast to charged Higgs bosons heavier than the top quark mass. For light charged Higgs bosons the decay via $H^\\pm \\to \\tau^\\pm \

QCD analysis of light charged Higgs production through polarized top quark decay in two different frames

Energy Technology Data Exchange (ETDEWEB)

Nejad, S. Mohammad Moosavi [Faculty of Physics, Yazd University,P.O. Box 89195-741, Yazd (Iran, Islamic Republic of); School of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM),P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Abbaspour, S. [Faculty of Physics, Yazd University,P.O. Box 89195-741, Yazd (Iran, Islamic Republic of)

2017-03-09

Light and heavy charged Higgs bosons are predicted by many models with an extended Higgs sector such as the two-Higgs-doublet model (2HDM). Searches for the charged Higgs bosons have been done by the ATLAS and the CMS experiments at the Large Hadron Collider (LHC) in proton-proton collision. However, a definitive search of charged Higgs bosons still has to be carried out by the LHC experiments. The experimental observation of charged Higgs bosons would indicate physics beyond the Standard Model. In the present work we study the O(α{sub s}) correction to the energy spectrum of the inclusive bottom-flavored mesons (X{sub b}) in polarized top quark decays into a light charged Higgs boson (m{sub H{sup +}}studied in two different helicity coordinate systems. This study could be considered as a new channel to indirect search for the charged Higgs bosons. To present our phenomenological predictions, we restrict ourselves to the constraints on the m{sub H{sup +}}−tan β parameter space determined by the recent results of the CMS and the ATLAS collaborations.

From photons to Higgs a story of light

CERN Document Server

Han, Moo-Young

2014-01-01

This book presents a brief introduction to the quantum field theory of the Standard Model for quarks and leptons. With minimal use of mathematics, it covers the basics of quantum field theory, local gauge field theory, spontaneous symmetry breaking mechanism, the Higgs mechanism and quantum chromodynamics. From the time when the first edition was published until today, the field of particle physics has seen some major break-through with the possible discovery of Higgs particle, also known as the Higgs boson. In the second edition, the famous Higgs mechanism is included to explain the symmetry breaking in the Standard Model and the origin of mass, and all of this is explained in high-school level algebra. Aimed at both scientists and non-specialists, it requires only some rudimentary knowledge of the Lagrangian and Hamiltonian formulation of Newtonian mechanics as well as a basic understanding of the special theory of relativity and quantum mechanics to enjoy this book.

Littlest Higgs with T-parity. Status and prospects

Energy Technology Data Exchange (ETDEWEB)

Reuter, Juergen; Tonini, Marco; Vries, Maikel de

2013-11-15

The Littlest Higgs model with T-parity is providing an attractive solution to the fine-tuning problem. This solution is only entirely natural if its intrinsic symmetry breaking scale f is relatively close to the electroweak scale. We examine the constraints using the latest results from the 8 TeV run at the LHC. Both direct searches and Higgs precision physics are taken into account. The constraints from Higgs couplings are by now competing with electroweak precision tests and both combined exclude f up to 694 GeV. At the same time limits from direct searches now become competitive and constrain f to be larger than 638 GeV. We show that the Littlest Higgs model parameter space is slowly driven into the TeV range. Furthermore, we develop a strategy on how to optimise present supersymmetry searches for the considered model, with the goal to improve the constraints and yield more stringent limits on f.

Higgs results from ATLAS

International Nuclear Information System (INIS)

Chen, Xin

2016-01-01

The updated Higgs measurements in various search channels with ATLAS Run 1 data are reviewed. Both the Standard Model (SM) Higgs results, such as H → γγ, ZZ, WW, ττ, μμ, bb-bar, and Beyond Standard Model (BSM) results, such as the charged Higgs, Higgs invisible decay and tensor couplings, are summarized. Prospects for future Higgs searches are briefly discussed

The Higgs Boson.

Science.gov (United States)

Veltman, Martinus J. G.

1986-01-01

Reports recent findings related to the particle Higgs boson and examines its possible contribution to the standard mode of elementary processes. Critically explores the strengths and uncertainties of the Higgs boson and proposed Higgs field. (ML)

Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables

CERN Document Server

Dittmaier, S; Passarino, G; Tanaka, R; Baglio, J; Bolzoni, P; Boughezal, R; Brein, O; Collins-Tooth, C; Dawson, S; Dean, S; Denner, A; Farrington, S; Felcini, M; Flechl, M; de Florian, D; Forte, S; Grazzini, M; Hackstein, C; Hahn, T; Harlander, R; Hartonen, T; Heinemeyer, S; Huston, J; Kalinowski, A; Krämer, M; Krauss, F; Lee, J S; Lehti, S; Maltoni, F; Mazumdar, K; Moch, S -O; Mück, A; Mühlleitner, M; Nason, P; Neu, C; Oleari, C; Olsen, J; Palmer, S; Petriello, F; Piacquadio, G; Pilaftsis, A; Potter, C T; Puljak, I; Qian, J; Rebuzzi, D; Reina, L; Rzehak, H; Schumacher, M; Slavich, P; Spira, M; Stöckli, F; Thorne, R S; Acosta, M Vazquez; Vickey, T; Vicini, A; Wackeroth, D; Warsinsky, M; Weber, M; Weiglein, G; Weydert, C; Yu, J; Zaro, M; Zirke, T

2011-01-01

This Report summarizes the results of the first 10 months' activities of the LHC Higgs Cross Sections Working Group. The main goal of the working group was to present the status-of-art on Higgs Physics at the LHC integrating all new results that have appeared in the last few years. The Report is more than a mere collection of the proceedings of the general meetings. The subgroups have been working in different directions. An attempt has been made to present the first Report from these subgroups in a complete and homogeneous form. The subgroups' contributions correspondingly comprise the main parts of the Report. A significant amount of work has been performed in providing higher-order corrections to the Higgs-boson cross sections and pinning down the theoretical uncertainty of the Standard Model predictions. This Report comprises explicit numerical results on total cross sections, leaving the issues of event selection cuts and differential distributions to future publications. The subjects for further study a...

Mass generation, the cosmological constant problem, conformal symmetry, and the Higgs boson

Science.gov (United States)

Mannheim, Philip D.

2017-05-01

In 2013 the Nobel Prize in Physics was awarded to Francois Englert and Peter Higgs for their work in 1964 along with the late Robert Brout on the mass generation mechanism (the Higgs mechanism) in local gauge theories. This mechanism requires the existence of a massive scalar particle, the Higgs boson, and in 2012 the Higgs boson was finally discovered at the Large Hadron Collider after being sought for almost half a century. In this article we review the work that led to the discovery of the Higgs boson and discuss its implications. We approach the topic from the perspective of a dynamically generated Higgs boson that is a fermion-antifermion bound state rather than an elementary field that appears in an input Lagrangian. In particular, we emphasize the connection with the Bardeen-Cooper-Schrieffer theory of superconductivity. We identify the double-well Higgs potential not as a fundamental potential but as a mean-field effective Lagrangian with a dynamical Higgs boson being generated through a residual interaction that accompanies the mean-field Lagrangian. We discuss what we believe to be the key challenge raised by the discovery of the Higgs boson, namely determining whether it is elementary or composite, and through study of a conformal invariant field theory model as realized with critical scaling and anomalous dimensions, suggest that the width of the Higgs boson might serve as a suitable diagnostic for discriminating between an elementary Higgs boson and a composite one. We discuss the implications of Higgs boson mass generation for the cosmological constant problem, as the cosmological constant receives contributions from the very mechanism that generates the Higgs boson mass in the first place. We show that the contribution to the cosmological constant due to a composite Higgs boson is more tractable and under control than the contribution due to an elementary Higgs boson, and is potentially completely under control if there is an underlying conformal

First Glimpses at Higgs' face

CERN Document Server

Espinosa, J.R.; Muhlleitner, M.; Trott, M.

2012-01-01

The 8 TeV LHC Higgs search data just released indicates the existence of a scalar resonance with mass ~ 125 GeV. We examine the implications of the data reported by ATLAS, CMS and the Tevatron collaborations on understanding the properties of this scalar by performing joint fits on its couplings to other Standard Model particles. We discuss and characterize to what degree this resonance has the properties of the Standard Model (SM) Higgs, and consider what implications can be extracted for New Physics in a (mostly) model-independent fashion. We find that, if the Higgs couplings to fermions and weak vector bosons are allowed to differ from their standard values, the SM is ~ 2 sigma from the best fit point to current data. Fitting to a possible invisible decay branching ratio, we find BR_{inv} = 0.05\\pm 0.32\\ (95% C.L.) We also discuss and develop some ways of using the data in order to bound or rule out models which modify significantly the properties of this scalar resonance and apply these techniques to the ...

Study Of Boosted W-Jets And Higgs-Jets With the SiFCC Detector

Energy Technology Data Exchange (ETDEWEB)

Yu, Shin-Shan [Taiwan, Natl. Central U.; Chekanov, Sergei [Argonne; Gray, Lindsey [Fermilab; Kotwal, Ashutosh [Duke U.; Sen, Sourav [Duke U.; Tran, Nhan Viet [Fermilab

2016-11-04

We study the detector performance in the reconstruction of hadronically-decaying W bosons and Higgs bosons at very high energy proton colliders using a full GEANT4 simulation of the SiFCC detector. The W and Higgs bosons carry transverse momentum in the multi-TeV range, which results in collimated decay products that are reconstructed as a single jet. We present a measurement of the energy response and resolution of boosted W-jets and Higgs-jets and show the separation of two sub-jets within the boosted boson jet.

On flavour and naturalness of composite Higgs models

International Nuclear Information System (INIS)

Matsedonskyi, Oleksii

2015-01-01

We analyse the interplay of the constraints imposed on flavour-symmetric Composite Higgs models by Naturalness considerations and the constraints derived from Flavour Physics and Electroweak Precision Tests. Our analysis is based on the Effective Field Theory which describes the Higgs as a pseudo-Nambu-Goldstone boson and also includes the composite fermionic resonances. Within this approach one is able to identify the directions in the parameter space where the U(3)-symmetric flavour models can pass the current experimental constraints, without conflicting with the light Higgs mass. We also derive the general features of the U(2)-symmetric models required by the experimental bounds, in case of elementary and totally composite t R . An effect in the Zb-barb coupling, which can potentially allow for sizable deviations in Z→b-barb decay parameters without modifying flavour physics observables, is identified. We also present the analysis of the mixed scenario, where the top quark mass is generated due to Partial Compositeness while the light quark masses are Technicolor-like.

A next-to-leading-log Monte Carlo study of photon pairs and the search for the intermediate mass Higgs Boson

International Nuclear Information System (INIS)

Bailey, B.R.

1993-01-01

Symmetry breaking and the question of the origin of mass are the reasons the Superconducting Super Collider and the Large Hadron Collider are being built. The Standard Model of particle physics provides a solution to this problem by proposing the existence of a neutral scalar particle, the Higgs boson. This particle, via its interactions, gives mass to all of the particles in the Standard Model. The question of whether the Higgs boson can be detected at these machines depends critically on its final state decays. These decays in turn depend crucially on the mass of the Higgs boson, an unknown parameter of the theory. A lower bound of the Higgs mass has been set by experiment and a upper bound via theoretical arguments. Throughout much of the mass range Higgs decays via weak gauge bosons yield a clear signal. However, near the lower limit, the so-called intermediate mass region, the situation is less clear. In this region Higgs decays into photon pairs have been suggested as a viable signal. The significance of such a signal depends on other competing processes or backgrounds. This dissertation attempts to answer the question, open-quotes Can the Intermediate mass Higgs boson be detected via its electromagnetic decays?close quotes To answer this question various Standard Model processes are calculated to the leading-log and next-to-leading-log level in a Monte Carlo environment

The Flavor of the Composite Pseudo-Goldstone Higgs

CERN Document Server

Csaki, Csaba; Weiler, Andreas

2008-01-01

We study the flavor structure of 5D warped models that provide a dual description of a composite pseudo-Goldstone Higgs. We first carefully re-examine the flavor constraints on the mass scale of new physics in the standard Randall-Sundrum-type scenarios, and find that the KK gluon mass should generically be heavier than about 21 TeV. We then compare the flavor structure of the composite Higgs models to those in the RS model. We find new contributions to flavor violation, which while still are suppressed by the RS-GIM mechanism, will enhance the amplitudes of flavor violations. In particular, there is a kinetic mixing term among the SM fields which (although parametrically not enhanced) will make the flavor bounds even more stringent than in RS, and imply the KK gluon mass to be at least about 33 TeV. For both the RS and the composite Higgs models the flavor bounds could be stronger or weaker depending on the assumption on the value of the gluon boundary kinetic term. These strong bounds seem to imply that the...

Discovery of the Higgs Boson Decaying to Two Photons

CERN Document Server

AUTHOR|(CDS)2075371; Branson, James; Pieri, Marco

2014-09-10

The Standard Model (SM) of particle physics fundamentally relies on the existence of the Higgs boson. This massive particle is a relic of the underlying and hidden Higgs field, whose transformation into the Higgs boson provides mass to weak bosons and all massive fermions in the SM. This particle has been long-sought and finally using data from proton-proton collisions at the LHC, CMS and ATLAS experiments have discovered a particle which is compatible with the SM Higgs boson. Presented here is the development of one of the discovery channels, $\\mathrm{H}\\rightarrow\\gamma\\gamma$, and the final $\\mathrm{H}\\rightarrow\\gamma\\gamma$ analysis and results using the full luminosity of the LHC Run 1 dataset $\\sim$25 $\\mathrm{fb}^{-1}$ at 7 or 8 TeV center of mass energy. The observed (expected) significance of this di-photon excess in the final analysis is $5.7\\sigma$ ($5.2\\sigma$) with a measured signal strength of $\\sigma / \\sigma_{SM} = 1.14^{+0.26}_{-0.23}$. The mass of this Higgs boson is not predicted by t...

Minimal spontaneously broken hidden sector and its impact on Higgs boson physics at the CERN Large Hadron Collider

International Nuclear Information System (INIS)

Schabinger, Robert; Wells, James D.

2005-01-01

Little experimental data bears on the question of whether there is a spontaneously broken hidden sector that has no Standard Model quantum numbers. Here we discuss the prospects of finding evidence for such a hidden sector through renormalizable interactions of the Standard Model Higgs boson with a Higgs boson of the hidden sector. We find that the lightest Higgs boson in this scenario has smaller rates in standard detection channels, and it can have a sizeable invisible final state branching fraction. Details of the hidden sector determine whether the overall width of the lightest state is smaller or larger than the Standard Model width. We compute observable rates, total widths and invisible decay branching fractions within the general framework. We also introduce the 'A-Higgs Model', which corresponds to the limit of a hidden sector Higgs boson weakly mixing with the Standard Model Higgs boson. This model has only one free parameter in addition to the mass of the light Higgs state and it illustrates most of the generic phenomenology issues, thereby enabling it to be a good benchmark theory for collider searches. We end by presenting an analogous supersymmetry model with similar phenomenology, which involves hidden sector Higgs bosons interacting with MSSM Higgs bosons through D-terms

The ATLAS Higgs Machine Learning Challenge

CERN Document Server

Cowan, Glen; The ATLAS collaboration; Bourdarios, Claire

2015-01-01

High Energy Physics has been using Machine Learning techniques (commonly known as Multivariate Analysis) since the 1990s with Artificial Neural Net and more recently with Boosted Decision Trees, Random Forest etc. Meanwhile, Machine Learning has become a full blown field of computer science. With the emergence of Big Data, data scientists are developing new Machine Learning algorithms to extract meaning from large heterogeneous data. HEP has exciting and difficult problems like the extraction of the Higgs boson signal, and at the same time data scientists have advanced algorithms: the goal of the HiggsML project was to bring the two together by a “challenge”: participants from all over the world and any scientific background could compete online to obtain the best Higgs to tau tau signal significance on a set of ATLAS fully simulated Monte Carlo signal and background. Instead of HEP physicists browsing through machine learning papers and trying to infer which new algorithms might be useful for HEP, then c...

Circular Higgs Factories & Possible Long-Term Strategy

CERN Document Server

Zimmermann, F

2013-01-01

In 2012 two LHC experiments have discovered a new particle with a mass around 125 GeV, which appears to be the scalar Higgs boson of the Standard Model. To further examine this remarkable particle it could be produced in large numbers for precision studies by an e+e− collider operating near the ZH threshold at beam energies of 120 GeV, or, in the s-channel by a gamma-gamma collider with primary electron beam energies of 80 GeV, or by a high-energy electron-proton collider. In this talk I will discuss tentative design parameters, novel concepts and accelerator-physics challenges (1) for a high-luminosity lepton-hadron collider, bringing into collision a 60-GeV electron beam from an energy-recovery electron linac with one of the LHC hadron beams – LHeC –, (2) for a gamma-gamma Higgs-factory collider based on the reconfigured recirculating SC electron linac – SAPPHiRE – and (3) for a circular e+e− Higgs-factory collider in a new tunnel with a circumference of 80-100 km – TLEP. I will also discuss f...

BSM Higgs Studies at the LHC in the Forward Proton Mode

CERN Document Server

Heinemeyer, S; Ryskin, M G; Tasevsky, M; Weiglein, G

2010-01-01

The prospects for central exclusive diffractive (CED) production of BSM Higgs bosons at the LHC are reviewed. This comprises the production of MSSM and 4th generation Higgs bosons. The sensitivity of the searches in the forward proton mode for the Higgs bosons as well as the possibility of a coupling structure determination are briefly discussed.

Boosting the Direct CP Measurement of the Higgs-Top Coupling.

Science.gov (United States)

Buckley, Matthew R; Gonçalves, Dorival

2016-03-04

Characterizing the 125 GeV Higgs boson is a critical component of the physics program at the LHC Run II. In this Letter, we consider tt[over ¯]H associated production in the dileptonic mode. We demonstrate that the difference in azimuthal angle between the leptons from top decays can directly reveal the CP structure of the top-Higgs coupling with the sensitivity of the measurement substantially enhanced in the boosted Higgs regime. We first show how to access this channel via H→bb[over ¯] jet-substructure tagging, then demonstrate the ability of the new variable to measure CP. Our analysis includes all signal and background samples simulated via the MC@NLO algorithm including hadronization and underlying-event effects. Using a boosted Higgs substructure with dileptonic tops, we find that the top-Higgs coupling strength and the CP structure can be directly probed with achievable luminosity at the 13 TeV LHC.

Corrections to di-Higgs boson production with light stops and modified Higgs couplings

Science.gov (United States)

Huang, Peisi; Joglekar, Aniket; Li, Min; Wagner, Carlos E. M.

2018-04-01

The Higgs pair production in gluon fusion is a sensitive probe of beyond-standard model (BSM) phenomena and its detection is a major goal for the LHC and higher energy hadron collider experiments. In this work we reanalyze the possible modifications of the Higgs pair production cross section within low energy supersymmetry models. We show that the supersymmetric contributions to the Higgs pair production cross section are strongly correlated with the ones of the single Higgs production in the gluon fusion channel. Motivated by the analysis of ATLAS and CMS Higgs production data, we show that the scalar superpartners' contributions may lead to significant modification of the di-Higgs production rate and invariant mass distribution with respect to the SM predictions. We also analyze the combined effects on the di-Higgs production rate of a modification of the Higgs trilinear and top-quark Yukawa couplings in the presence of light stops. In particular, we show that due to the destructive interference of the triangle and box amplitude contributions to the di-Higgs production cross section, even a small modification of the top-quark Yukawa coupling can lead to a significant increase of the di-Higgs production rate.

Dark side of the Higgs boson

International Nuclear Information System (INIS)

Low, I.; Schwaller, P.; Shaughnessy, G.; Wagner, C.E.M.

2012-01-01

Current limits from the Large Hadron Collider exclude a standard model-like Higgs mass above 150 GeV, by placing an upper bound on the Higgs production rate. We emphasize that, alternatively, the limit could be interpreted as a lower bound on the total decay width of the Higgs boson. If the invisible decay width of the Higgs is of the same order as the visible decay width, a heavy Higgs boson could be consistent with null results from current searches. We propose a method to infer the invisible decay of the Higgs by using the width of the measured h → ZZ → 4 (ell) line shape, and study the effect on the width extraction due to a reduced signal strength. Assuming the invisible decay product is the dark matter, we show that minimal models are tightly constrained by limits from Higgs searches at the LHC and direct detection experiments of dark matter, unless the relic density constraint is relaxed.

Searching for additional Higgs bosons via Higgs cascades

Science.gov (United States)

Gao, Christina; Luty, Markus A.; Mulhearn, Michael; Neill, Nicolás A.; Wang, Zhangqier

2018-04-01

The discovery of a 125 GeV Higgs boson at the Large Hadron Collider strongly motivates direct searches for additional Higgs bosons. In a type I two Higgs doublet model there is a large region of parameter space at tan β ≳5 that is currently unconstrained experimentally. We show that the process g g →H →A Z →Z Z h can probe this region, and can be the discovery mode for an extended Higgs sector at the LHC. We analyze 9 promising decay modes for the Z Z h state, and we find that the most sensitive final states are ℓℓℓℓb b , ℓℓj j b b , ℓℓν ν γ γ and ℓℓℓℓ+ missing energy.

Higgs and confinement phases in the fundamental SU(2) Higgs model: Mean field analysis

International Nuclear Information System (INIS)

Damgaard, P.H.; Heller, U.M.

1985-01-01

The phase diagram of the four-dimensional SU(2) gauge-Higgs model with Higgs field in the fundamental representation is derived by mean field techniques. When the Higgs field is allowed to fluctuate in. Magnitude, the analytic connection between Higgs and confinement phases breaks down for sufficiently small values of the quark Higgs coupling, indicating that the Higgs and confinement phases for these couplings are strictly distinct phases. (orig.)

What is the probability of the Higgs boson discovery?

Energy Technology Data Exchange (ETDEWEB)

Unzicker, Alexander [Pestalozzi-Gymnasium Muenchen (Germany)

2010-07-01

The standard model of particle physics requires the existence of the Higgs boson which provides a mechanism for the appearance of masses. Its detection is one of the most important goals of high energy physics, and enormous efforts have been undertaken at Tevatron and specially at the Large Hadron Collider. But how sure can we be that the Higgs exits at all? At such controversial questions, the German philosopher Immanuel Kant recommended a bet, and nowadays this can be realized using online prediction markets like Intrade.com. Such platforms have been proven useful for giving estimates of unknown probabilities, and the application for evaluating scientific research is discussed in general.

The fate of the Higgs vacuum

Energy Technology Data Exchange (ETDEWEB)

Burda, Philipp [Racah Institute of Physics, Hebrew University,Jerusalem 91904 (Israel); Centre for Particle Theory, Durham University,South Road, Durham, DH1 3LE (United Kingdom); Gregory, Ruth [Centre for Particle Theory, Durham University,South Road, Durham, DH1 3LE (United Kingdom); Perimeter Institute,31 Caroline Street North, Waterloo, ON, N2L 2Y5 (Canada); Moss, Ian G. [School of Mathematics and Statistics, Newcastle University,Newcastle Upon Tyne, NE1 7RU (United Kingdom)

2016-06-06

We have recently suggested that tiny black holes can act as nucleation seeds for the decay of the metastable Higgs vacuum. Previous results applied only to the nucleation of thin-wall bubbles, and covered a very small region of parameter space. This paper considers bubbles of arbitrary profile and reaches the same conclusion: black holes seed rapid vacuum decay. Seeded and unseeded nucleation rates are compared, and the gravitational back reaction of the bubbles is taken into account. The evolution of the bubble interior is described for the unseeded nucleation. Results are presented for the renormalisation group improved Standard Model Higgs potential, and a simple effective model representing new physics.

The fate of the Higgs vacuum

International Nuclear Information System (INIS)

Burda, Philipp; Gregory, Ruth; Moss, Ian G.

2016-01-01

We have recently suggested that tiny black holes can act as nucleation seeds for the decay of the metastable Higgs vacuum. Previous results applied only to the nucleation of thin-wall bubbles, and covered a very small region of parameter space. This paper considers bubbles of arbitrary profile and reaches the same conclusion: black holes seed rapid vacuum decay. Seeded and unseeded nucleation rates are compared, and the gravitational back reaction of the bubbles is taken into account. The evolution of the bubble interior is described for the unseeded nucleation. Results are presented for the renormalisation group improved Standard Model Higgs potential, and a simple effective model representing new physics.

Can We Tell Students where the Higgs Boson Lies?

Science.gov (United States)

Chu, Z. Kwang-Hua

2010-01-01

We pedagogically introduce the search for the Higgs boson and the measurement of its properties which will be one of the primary goals of the Large Hadron Collider. Our presentation will be useful to the relevant graduate and senior undergraduate students studying physics, as well as researchers in this field. (Contains 1 figure.)

C P -violation in the two Higgs doublet model: From the LHC to EDMs

Science.gov (United States)

Chen, Chien-Yi; Li, Hao-Lin; Ramsey-Musolf, Michael

2018-01-01

We study the prospective sensitivity to C P -violating two Higgs doublet models from the 14 TeV LHC and future electric dipole moment (EDM) experiments. We concentrate on the search for a resonant heavy Higgs that decays to a Z boson and a SM-like Higgs h , leading to the Z (ℓℓ)h (b b ¯ ) final state. The prospective LHC reach is analyzed using the Boosted Decision Tree method. We illustrate the complementarity between the LHC and low energy EDM measurements and study the dependence of the physics reach on the degree of deviation from the alignment limit. In all cases, we find that there exists a large part of parameter space that is sensitive to both EDMs and LHC searches.

Test of the little Higgs model in Atlas at LHC: simulation of the digitization of the electromagnetic calorimeter; Test du modele du petit Higgs dans ATLAS au LHC: simulation de la numerisation du calorimetre electromagnetique

Energy Technology Data Exchange (ETDEWEB)

Lechowski, M

2005-04-15

LHC is a proton-proton collider with an energy of 14 TeV in the center of mass, which will start operating in 2007 at CERN. Two of its experiments, ATLAS, and CMS, will search and study in particular the Higgs boson, Supersymmetry and other new physics. This thesis was about two aspects of the ATLAS experiment. On one hand the simulation of the liquid Argon electromagnetic calorimeter, with the emulation of the electronic chain in charge of the digitization of the signal and also the evaluation of the electronic noise and the pile-up noise (coming from minimum bias events of inelastic collisions at LHC). These two points have been validated by the analysis of the data taken during beam tests in 2002 and 2004. On the other hand, a physics study concerning the Little Higgs model. This recent model solves the hierarchy problem of the Standard Model, in introducing new heavy particles to cancel quadratic divergences arising in the calculation of the Higgs boson mass. These new particles, with a mass about the TeV/c{sup 2}, are a heavy quark top, heavy gauge bosons Z{sub H}, W{sub H} and A{sub H}, and a heavy Higgs boson triplet. The physics study dealt with the characteristic decays of the model, Z{sub H} in Z + H and W{sub H} in W + H, with a Higgs mass either at 120 GeV/c{sup 2} decaying in two photons or at 200 GeV/c{sup 2} decaying in ZZ or WW. Results show that in both cases, for 300 fb{sup -1} (3 years at high luminosity), an observation of the signal at 5 {sigma} for Z{sub H} et W{sub H} masses less than 2 TeV/c{sup 2} is possible, covering a large part of the parameter space. (author)

Higgs Boson Pizza Day

CERN Document Server

Stefania Pandolfi

2016-01-01

CERN celebrated the fourth anniversary of the historical Higgs boson announcement with special pizzas.    400 pizzas were served on Higgs pizza day in Restaurant 1 at CERN to celebrate the fourth anniversary of the announcement of the discovery of the Higgs Boson (Image: Maximilien Brice/ CERN) What do the Higgs boson and a pizza have in common? Pierluigi Paolucci, INFN and CMS collaboration member, together with INFN president Fernando Ferroni found out the answer one day in Naples: the pizza in front of them looked exactly like a Higgs boson event display. A special recipe was then created in collaboration with the chef of the historic “Ettore” pizzeria in the St. Lucia area of Naples, and two pizzas were designed to resemble two Higgs boson decay channel event displays. The “Higgs Boson Pizza Day” was held on Monday, 4 July 2016, on the fourth anniversary of the announcement of the discovery of the Higgs boso...

Smoking-gun signatures of little Higgs models

Energy Technology Data Exchange (ETDEWEB)

Han Tao [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States); Institute of Theoretical Physics, Academia Sinica, Beijing 100080 (China); Logan, Heather E. [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States); Wang, L.-T. [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States); Jefferson Laboratory of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States)

2006-01-15

Little Higgs models predict new gauge bosons, fermions and scalars at the TeV scale that stabilize the Higgs mass against quadratically divergent one-loop radiative corrections. We categorize the many little Higgs models into two classes based on the structure of the extended electroweak gauge group and examine the experimental signatures that identify the little Higgs mechanism in addition to those that identify the particular little Higgs model. We find that by examining the properties of the new heavy fermion(s) at the LHC, one can distinguish the structure of the top quark mass generation mechanism and test the little Higgs mechanism in the top sector. Similarly, by studying the couplings of the new gauge bosons to the light Higgs boson and to the Standard Model fermions, one can confirm the little Higgs mechanism and determine the structure of the extended electroweak gauge group.

Distinguishing a SM-like MSSM Higgs boson from SM Higgs boson ...

Indian Academy of Sciences (India)

The Higgs sector of the MSSM contains two scalar doublet fields leading to five ... At tree level, the masses and couplings of the MSSM Higgs bosons ..... J F Gunion, H E Haber, G Kane and S Dawson, The Higgs Hunters Guide (Addison-.

Upper and lower Higgs boson mass bounds from a lattice Higgs-Yukawa model with dynamical overlap fermions

International Nuclear Information System (INIS)

Gerhold, Philipp; Jansen, Karl

2009-12-01

We study a lattice Higgs-Yukawa model emulating the same Higgs-fermion coupling structure as in the Higgs sector of the electroweak Standard Model, in particular, obeying a Ginsparg- Wilson version of the underlying SU(2) L x U(1) Y symmetry, being a global symmetry here due to the neglection of gauge fields in this model. In this paper we present our results on the cutoffdependent upper Higgs boson mass bound at several selected values of the cutoff parameter Λ. (orig.)

Charged and neutral minimal supersymmetric standard model Higgs ...

Indian Academy of Sciences (India)

physics pp. 759–763. Charged and neutral minimal supersymmetric standard model Higgs boson decays and measurement of tan β at the compact linear collider. E CONIAVITIS and A FERRARI∗. Department of Nuclear and Particle Physics, Uppsala University, 75121 Uppsala, Sweden. ∗E-mail: ferrari@tsl.uu.se. Abstract.

Electroweak precision observables and Higgs-boson signal strengths in the Standard Model and beyond: present and future

Energy Technology Data Exchange (ETDEWEB)

Blas, J. de [INFN, Sezione di Roma,Piazzale A. Moro 2, I-00185 Rome (Italy); Ciuchini, M. [INFN, Sezione di Roma Tre,Via della Vasca Navale 84, I-00146 Roma (Italy); Franco, E. [INFN, Sezione di Roma,Piazzale A. Moro 2, I-00185 Rome (Italy); Mishima, S. [Theory Center, Institute of Particle and Nuclear Studies (IPNS),High Energy Accelerator Research Organization (KEK),1-1 Oho, Tsukuba, 305-0801 (Japan); Pierini, M. [CERN,Geneva (Switzerland); Reina, L. [Physics Department, Florida State University,77 Chieftan Way, Tallahassee, FL 32306-4350 (United States); Kavli Institute for Theoretical Physics, University of California,Kohn Hall, Santa Barbara, CA 93106-4030 (United States); Silvestrini, L. [INFN, Sezione di Roma,Piazzale A. Moro 2, I-00185 Rome (Italy)

2016-12-27

We present results from a state-of-the-art fit of electroweak precision observables and Higgs-boson signal-strength measurements performed using 7 and 8 TeV data from the Large Hadron Collider. Based on the HEPfit package, our study updates the traditional fit of electroweak precision observables and extends it to include Higgs-boson measurements. As a result we obtain constraints on new physics corrections to both electroweak observables and Higgs-boson couplings. We present the projected accuracy of the fit taking into account the expected sensitivities at future colliders.

The Higgs Particle: A Useful Analogy for Physics Classrooms

Science.gov (United States)

Cid, Xabier; Cid, Ramon

2010-01-01

In November 2009, the largest experiment in history was restarted. Its prime target is the Higgs particle--the last remaining undiscovered piece of our current theory of matter. We present a very simple way to introduce this topic to senior secondary school students, using a comparison with the refractive index of light.

Penguin effects induced by the two-Higgs-doublet model and charmless B-meson decays

International Nuclear Information System (INIS)

Davies, A.J.; Joshi, G.C.; Matsuda, M.

1991-01-01

Nonstandard physical effects through the penguin diagram induced by the charged Higgs scalar contribution in the two-Higgs-doublet model are analysed. Since non-leptonic B-decay processes to final states consisting of s+s+anti s are induced only through the penguin diagram they are important tests of such contributions. We compare these decays including the non-standard two-Higgs-doublet contribution with the standard model results, which arise from the magnetic gluon transistion term. The charged Higgs contribution can give a sizable enhancement to the branching fraction of B-meson charmless decay. (orig.)

The U(1)-Higgs model: critical behaviour in the confining-Higgs region

International Nuclear Information System (INIS)

Alonso, J.L.; Azcoiti, V.; Campos, I.; Ciria, J.C.; Cruz, A.; Iniguez, D.; Lesmes, F.; Piedrafita, C.; Rivero, A.; Tarancon, A.; Badoni, D.; Fernandez, L.A.; Munoz Sudupe, A.; Ruiz-Lorenzo, J.J.; Gonzalez-Arroyo, A.; Martinez, P.; Pech, J.; Tellez, P.

1993-01-01

We study numerically the critical properties of the U(1)-Higgs lattice model, with fixed Higgs modulus, in the region of small gauge coupling where the Higgs and confining phases merge. We find evidence for a first-order transition line that ends in a second-order point. By means of a rotation in parameter space we introduce thermodynamic magnitudes and critical exponents in close resemblance with simple models that show analogous critical behaviour. The measured data allow us to fit the critical exponents finding values in agreement with the mean-field prediction. The location of the critical point and the slope of the first-order line are accurately measured. (orig.)

Search for new resonances involving Higgs, W or Z boson at CMS

CERN Document Server

Rappoccio, Salvatore

2016-01-01

Beyond the standard model theories like composite Higgs models predict resonances with large branching fractions in a Higgs boson and a vector boson with negligible branching fractions to light fermions. We present an overview of searches for new physics containing a Higgs boson and a W or Z boson in the final state, using proton-proton collision data collected with the CMS detector at the CERN LHC. For high-mass resonances decaying to intermediate bosons, the large boost for hadronic decays gives rise to one single merged jet, which can be identified through a study of its substructure consistent with the presence of two quarks, enhancing the sensitivity due to the large branching ratios for hadronic decays. B-quark identification algorithms are used in addition to identify the hadronic H decays.

Naturally large radiative lepton flavor violating Higgs decay mediated by lepton-flavored dark matter

International Nuclear Information System (INIS)

Baek, Seungwon; Kang, Zhaofeng

2016-01-01

In the standard model (SM), lepton flavor violating (LFV) Higgs decay is absent at renormalizable level and thus it is a good probe to new physics. In this article we study a type of new physics that could lead to large LFV Higgs decay, i.e., a lepton-flavored dark matter (DM) model which is specified by a Majorana DM and scalar lepton mediators. Different from other similar models with similar setup, we introduce both left-handed and right-handed scalar leptons. They allow large LFV Higgs decay and thus may explain the tentative Br(h→τμ)∼1% experimental results from the LHC. In particular, we find that the stringent bound from τ→μγ can be naturally evaded. One reason, among others, is a large chirality violation in the mediator sector. Aspects of relic density and especially radiative direct detection of the leptonic DM are also investigated, stressing the difference from previous lepton-flavored DM models.

The universal Higgs fit

DEFF Research Database (Denmark)

Giardino, P. P.; Kannike, K.; Masina, I.

2014-01-01

We perform a state-of-the-art global fit to all Higgs data. We synthesise them into a 'universal' form, which allows to easily test any desired model. We apply the proposed methodology to extract from data the Higgs branching ratios, production cross sections, couplings and to analyse composite...... Higgs models, models with extra Higgs doublets, supersymmetry, extra particles in the loops, anomalous top couplings, and invisible Higgs decays into Dark Matter. Best fit regions lie around the Standard Model predictions and are well approximated by our 'universal' fit. Latest data exclude the dilaton...... as an alternative to the Higgs, and disfavour fits with negative Yukawa couplings. We derive for the first time the SM Higgs boson mass from the measured rates, rather than from the peak positions, obtaining M-h = 124.4 +/- 1.6 GeV....

A Geometrical View of Higgs Effective Theory

CERN Multimedia

CERN. Geneva

2016-01-01

A geometric formulation of Higgs Effective Field Theory (HEFT) is presented. Experimental observables are given in terms of geometric invariants of the scalar sigma model sector such as the curvature of the scalar field manifold M. We show how the curvature can be measured experimentally via Higgs cross-sections, W_L scattering, and the S parameter. The one-loop action of HEFT is given in terms of geometric invariants of M. The distinction between the Standard Model (SM) and HEFT is whether M is flat or curved, with the curvature a signal of the scale of new physics.

Impact of generalized Yukawa interactions on the lower Higgs-mass bound

Energy Technology Data Exchange (ETDEWEB)

Gies, Holger [Friedrich-Schiller-Universitaet Jena, Theoretisch-Physikalisches Institut, Jena (Germany); Friedrich-Schiller-Universitaet Jena, Abbe Center of Photonics, Jena (Germany); Helmholtz-Institut Jena, Jena (Germany); Sondenheimer, Rene [Friedrich-Schiller-Universitaet Jena, Theoretisch-Physikalisches Institut, Jena (Germany); Warschinke, Matthias [Friedrich-Schiller-Universitaet Jena, Theoretisch-Physikalisches Institut, Jena (Germany); Chiba University, Department of Physics, Graduate School of Science, Chiba (Japan)

2017-11-15

We investigate the impact of operators of higher canonical dimension on the lower Higgs-mass consistency bound by means of generalized Higgs-Yukawa interactions. Analogously to higher-order operators in the bare Higgs potential in an effective field theory approach, the inclusion of higher-order Yukawa interactions, e.g., φ{sup 3} anti ψψ, leads to a diminishing of the lower Higgs-mass bound and thus to a shift of the scale of new physics towards larger scales by a few orders of magnitude without introducing a metastability in the effective Higgs potential. We observe that similar renormalization group mechanisms near the weak-coupling fixed point are at work in both generalizations of the microscopic action. Thus, a combination of higher-dimensional operators with generalized Higgs as well as Yukawa interactions does not lead to an additive shift of the lower mass bound, but it relaxes the consistency bounds found recently only slightly. On the method side, we clarify the convergence properties of different projection and expansion schemes for the Yukawa potential used in the functional renormalization group literature so far. (orig.)

Cosmological perturbations in the new Higgs inflation

Energy Technology Data Exchange (ETDEWEB)

Germani, Cristiano [Arnold Sommerfeld Center, Ludwig-Maximilians-University, Theresienstr, 37 80333 Muenchen (Germany); Kehagias, Alex, E-mail: cristiano.germani@lmu.de, E-mail: kehagias@central.ntua.gr [Physics Division, National Technical University of Athens, 15780 Zografou Campus, Athens (Greece)

2010-05-01

We study the cosmological perturbations created during the New Higgs inflationary phase. In the New Higgs Inflation, the Higgs boson is kinetically coupled to the Einstein tensor and only three perturbative degrees of freedom, a scalar and two tensorial (gravitational waves), propagate during Inflation. Scalar perturbations are found to match the latest WMAP-7yrs data within Standard Model Higgs parameters. Primordial gravitational waves also, although propagating with superluminal speed, are consistent with present data. Finally, we estimate the values of the parameter of the New Higgs Inflation in relation to the Higgs mass, the spectral index and amplitude of the primordial scalar perturbations showing that the unitarity bound of the theory is not violated.

Physics at CLIC

CERN Multimedia

CERN. Geneva

2017-01-01

The Compact Linear Collider (CLIC) is a high-energy e+e- collider under development. The CLIC conceptual design report, published in 2012, concentrated on 3 TeV centre-of-mass energy. At that time operation at lower energies was not yet studied at the same level. Following the discovery of the Higgs boson, the CLIC potential for precision Higgs measurements was addressed for several centre-of-mass energies. In parallel, the scope for precision top quark physics was further explored. As a result an optimised CLIC staging scenario was defined in collaboration between accelerator and detector experts. The staging scenario aims at a maximum physics output and maximum luminosity yield with a collider built and operated in three energy steps: 380 GeV, 1.5 TeV, 3 TeV. The seminar will comprise a short status report on the CLIC accelerator and detector. Emphasis will be on the CLIC physics potential for Higgs, top quark and BSM physics in the new staging scenario.

Higgs mechanism and the added-mass effect.

Science.gov (United States)

Krishnaswami, Govind S; Phatak, Sachin S

2015-04-08

In the Higgs mechanism, mediators of the weak force acquire masses by interacting with the Higgs condensate, leading to a vector boson mass matrix. On the other hand, a rigid body accelerated through an inviscid, incompressible and irrotational fluid feels an opposing force linearly related to its acceleration, via an added-mass tensor. We uncover a striking physical analogy between the two effects and propose a dictionary relating them. The correspondence turns the gauge Lie algebra into the space of directions in which the body can move, encodes the pattern of gauge symmetry breaking in the shape of an associated body and relates symmetries of the body to those of the scalar vacuum manifold. The new viewpoint is illustrated with numerous examples, and raises interesting questions, notably on the fluid analogues of the broken symmetry and Higgs particle, and the field-theoretic analogue of the added mass of a composite body.

The Curious Ontology of a Light Higgs Boson

Science.gov (United States)

Riordan, Michael

2016-03-01

When the Superconducting Super Collider was being contemplated and designed in the mid-1980s, few high-energy physicists considered it likely that a light Higgs boson, as was eventually discovered at the Large Hadron Collider, would exist. Most theorists expected that the Higgs boson would occur at a mass near the TeV scale, and accelerator physicists designed the Super Collider accordingly. The possibility of a light Higgs boson with a mass less than 200 GeV began to be taken seriously during the 1990s, especially after the 1995 Fermilab discovery of the top quark near 175 GeV, but it was too late to influence the SSC design. With a peak collision energy of 40 TeV, this collider was guaranteed to discover the Higgs boson -- or whatever other mass-generating phenomenon might be occurring in the Standard Model -- even if it were to appear at masses or energies up to 2 TeV. As it turned out, therefore, the SSC was overdesigned for its principal physics goal. A substantially smaller Fermilab project known as the Dedicated Collider, which never made it beyond the drawing boards, could probably have allowed the 125 GeV Higgs boson to be discovered at least a decade earlier than it occurred at the LHC.

Character Profile of the Higgs boson

OpenAIRE

Brenner, Lydia; Verkerke, Wouter; Bentvelsen, Stan; Ferrari, Pamela

2017-01-01

Elementary particle physics describes and measures the properties of the smallest, most fundamental particles that make up the universe. The Standard Model of elementary particle physics provides a fundamental description of particles, their dynamics and interactions. The particles embedded into the theory are, a priori, massless, while observed particles have mass. In order to explain the origin of the elementary particle masses, the Brout-Englert-Higgs mechanism is introduced. The mechanism...

Character profile of the Higgs boson

OpenAIRE

Brenner, L.

2017-01-01

Elementary particle physics describes and measures the properties of the smallest, most fundamental particles that make up the universe. The Standard Model of elementary particle physics provides a fundamental description of particles, their dynamics and interactions. The particles embedded into the theory are, a priori, massless, while observed particles have mass. In order to explain the origin of the elementary particle masses, the Brout-Englert-Higgs mechanism is introduced. The mechanism...

Higgs boson hunting

International Nuclear Information System (INIS)

Dawson, S.; Haber, H.E.; Rindani, S.D.

1989-05-01

This is the summary report of the Higgs Boson Working Group. We discuss a variety of search techniques for a Higgs boson which is lighter than the Z. The processes K → πH, η prime → ηH,Υ → Hγ and e + e - → ZH are examined with particular attention paid to theoretical uncertainties in the calculations. We also briefly examine new features of Higgs phenomenology in a model which contains Higgs triplets as well as the usual doublet of scalar fields. 33 refs., 6 figs., 1 tab

Renormalization of the Abelian–Higgs model in the Rξ and Unitary gauges and the physicality of its scalar potential

Directory of Open Access Journals (Sweden)

Nikos Irges

2017-11-01

Full Text Available We perform an old school, one-loop renormalization of the Abelian–Higgs model in the Unitary and Rξ gauges, focused on the scalar potential and the gauge boson mass. Our goal is to demonstrate in this simple context the validity of the Unitary gauge at the quantum level, which could open the way for an until now (mostly avoided framework for loop computations. We indeed find that the Unitary gauge is consistent and equivalent to the Rξ gauge at the level of β-functions. Then we compare the renormalized, finite, one-loop Higgs potential in the two gauges and we again find equivalence. This equivalence needs not only a complete cancellation of the gauge fixing parameter ξ from the Rξ gauge potential but also requires its ξ-independent part to be equal to the Unitary gauge result. We follow the quantum behavior of the system by plotting Renormalization Group trajectories and Lines of Constant Physics, with the former the well known curves and with the latter, determined by the finite parts of the counter-terms, particularly well suited for a comparison with non-perturbative studies.

Minkowski space structure of the Higgs potential in the two-Higgs-doublet model. II. Minima, symmetries, and topology

International Nuclear Information System (INIS)

Ivanov, I. P.

2008-01-01

We continue to explore the consequences of the recently discovered Minkowski space structure of the Higgs potential in the two-Higgs-doublet model. Here, we focus on the vacuum properties. The search for extrema of the Higgs potential is reformulated in terms of 3-quadrics in the 3+1-dimensional Minkowski space. We prove that 2HDM cannot have more than two local minima in the orbit space and that a twice-degenerate minimum can arise only via spontaneous violation of a discrete symmetry of the Higgs potential. Investigating topology of the 3-quadrics, we give concise criteria for existence of noncontractible paths in the Higgs orbit space. We also study explicit symmetries of the Higgs potential/Lagrangian and their spontaneous violation from a wider perspective than usual

Precision predictions for Higgs differential distributions at the LHC

Energy Technology Data Exchange (ETDEWEB)

Ebert, Markus

2017-08-15

After the discovery of a Standard-Model-like Higgs boson at the LHC a central aspect of the LHC physics program is to study the Higgs boson's couplings to Standard Model particles in detail in order to elucidate the nature of the Higgs mechanism and to search for hints of physics beyond the Standard Model. This requires precise theory predictions for both inclusive and differential Higgs cross sections. In this thesis we focus on the application of resummation techniques in the framework of Soft-Collinear Effective Theory (SCET) to obtain accurate predictions with reliable theory uncertainties for various observables. We first consider transverse momentum distributions, where the resummation of large logarithms in momentum (or distribution) space has been a long-standing open question. We show that its two-dimensional nature leads to additional difficulties not observed in one-dimensional observables such as thrust, and solving the associated renormalization group equations (RGEs) in momentum space thus requires a very careful scale setting. This is achieved using distributional scale setting, a new technique to solve differential equations such as RGEs directly in distribution space, as it allows one to treat logarithmic plus distributions like ordinary logarithms. We show that the momentum space solution fundamentally differs from the standard resummation in Fourier space by different boundary terms to all orders in perturbation theory and hence provides an interesting and complementary approach to obtain new insight into the all-order perturbative and nonperturbative structure of transverse momentum distributions. Our work lays the ground for a detailed numerical study of the momentum space resummation. We then show that in the case of a discovery of a new heavy color-singlet resonance such as a heavy Higgs boson, one can reliably and model-independently infer its production mechanism by dividing the data into two mutually exclusive jet bins. The method is

Gauge field copies and Higgs mechanism

International Nuclear Information System (INIS)

Gleiser, M.

1982-07-01

From the algebric classification of the possible solutions of the necessary and sufficient condition for the existence of gauge field copies in two possible classes the Higgs mechanism for the potential obtained from the difference between two copied potentials is applied. It is shown that for class I 'electric type' it is possible to construct a vector field that satisfies an electromagnetic wave equation. For class I 'magnetic type', a vector field that satisfies a non-linear equation as a consequence of the non-abelianity of the theory, is obtained. It is shown that for class II it's not possible to apply the Higgs mechanism. A possible physical interpretation for the 'gauge field copies' phenomenon, is obtained. (author) [pt

Rencontres de Moriond EW 2012: Impact of a Higgs boson on supersymmetry

CERN Document Server

Pauline Gagnon

2012-01-01

Yesterday at the Moriond conference, several theorists addressed the consequences of the current Higgs boson searches on models going beyond the Standard Model.   Nazila Farvah Mahmoudi from CERN presented a study on the impact of a Higgs boson at 125 GeV on various supersymmetry (SUSY) models. So what would happen if indeed there is a Standard Model Higgs between 123 GeV and 127 GeV? The results are stunning: If all the recent limits from flavor physics are included, like the latest Bs to two muons measurement from LHCb, the limits from CMS on direct searches for SUSY, and assuming maximal mixing, then only a narrow band at low value of tan beta - one of the key parameters in SUSY - at or lower than 5 survive. At this value, mA, the mass of one of the five Higgs bosons predicted by SUSY, should be found between 200 and 500 GeV. This study done in collaboration with A. Arbey, M. Battaglia, A. Djouadi and J. Quévillon used the pMSSM model, a supersymmetric model with 19 free parameters...