Higgs mass and inflation

We show that the standard-model Higgs boson mass mh is correlated with the spectral index of density perturbation ns in the inflation scenario with the inflaton being identified with the B-L Higgs boson. The Higgs boson mass ranges from mh?120 GeV to 140 GeV for ns?0.95-0.96. In particular, as ns approaches to 0.96, the Higgs mass is predicted to be in the range of 125 GeV to 140 GeV in the case of relatively light gauginos, and 120 GeV to 135 GeV in the case where all SUSY particle masses are of the same order. This will be tested soon by the LHC experiment and the Planck satellite. The relation is due to the PeV-scale supersymmetry required by the inflationary dynamics. We also comment on the cosmological implications of our scenario such as non-thermal leptogenesis and dark matter.     

Higgs bosons in the simplest SUSY models

Nowadays, in the MSSM, the moderate values of tan β are almost excluded by the LEP II lower bound on the mass of the lightest Higgs boson. In the next-to-minimal supersymmetric standard model (NMSSM), the theoretical upper bound on it increases and reaches a maximal value in the limit of strong Yukawa coupling, where all solutions to renormalization-group equations are concentrated near the quasifixed point. For a calculation of the Higgs boson spectrum, the perturbation-theory method can be applied. We investigate the particle spectrum within the modified NMSSM, which leads to the self-consistent solution in the limit of strong Yukawa coupling. This model allows one to get m _h～125 GeV at tan β≥1.9. In the model under investigation, the mass of the lightest Higgs boson does not exceed 130.5±3.5 GeV. The upper bound on the mass of the lightest CP-even Higgs boson in more complicated supersymmetric models is also discussed.     

Particle spectrum in the modified nonminimal supersymmetric standard model in the strong Yukawa coupling regime

A theoretical analysis of solutions of renormalization group equations in the minimal supersymmetric standard model, which lead to a quasi-fixed point has shown that the mass of the lightest Higgs boson in these models does not exceed 94 ± 5 GeV. This implies that a considerable part of the parameter space in the minimal supersymmetric model is in fact eliminated by existing LEPII experimental data. In the nonminimal supersymmetric standard model the upper bound on the mass of the lightest Higgs boson reaches its maximum in the strong Yukawa coupling regime when the Yukawa constants are substantially greater than the gauge constants on the grand unification scale. In the present paper the particle spectrum is studied using the simplest modification of the nonminimal supersymmetric standard model which gives a self-consistent solution in this region of parameter space. This model can give m _h ～ 125 GeV even for comparatively low values of β ≥ 1.9. The spectrum of Higgs bosons and neutralinos is analyzed using the method of diagonalizing mass matrices proposed earlier. In this model the mass of the lightest Higgs boson does not exceed 130.5 ± 3.5 GeV.     

Searching for the Higgs at SLC and lep

We compute the cross section for the process e⁺e⁻ →Hff as a function of Higgs boson mass and of center-of-mass energies of M_z and beyond. We conclude that searches for a Higgs of mass less than 50 GeV are far more effective when carried out near the Z boson resonance that at any higher energy. However, a new window of Higgs boson masses extending from 50–107 GeV can be explored if and when e⁺e⁻ collisions can be studied with high luminosity at collision energies of 200 GeV. Collider energies at intermediate energies can play no useful role in the search for the Higgs.     

Vector Gauge Boson Dark Matter for the SU(N) Gauge Group Model

The existence of dark matter is explained by a new neutral vector boson, C-boson, of mass (900 GeV), predicted by the Wu mechanisms for mass generation of gauge field. According to the Standard Model (SM) W, Z-bosons normally get their masses through coupling with the SM Higgs particle of mass 125 GeV. We compute the self-annihilation cross section of the vector gauge boson C-dark matter and calculate its relic abundance. We also study the constraints suggested by dark-matter direct-search experiments. The problem on the stability of C-particle is left as an open question for future research.     

Mass of the Higgs-like boson in the four lepton decay channel at the LHC

A very simple and transparent way for the mass definition of a new boson, probably Higgs (H), observed at LHC, decaying into 4 leptons is presented. The obtained mass of H is 125.5 ± 0.4 GeV with today statistics.     

The fourth Standard Model family and the competition in Standard Model Higgs boson search at Tevatron and LHC

The impact of the fourth Standard Model family on Higgs boson search at Tevatron and LHC is reviewed. The enhancement due to a fourth SM family in the production of Higgs boson via gluon fusion already enables the Tevatron experiments to become sensitive to Higgs masses between 140 and 200 GeV and could increase this sensitivity up to about 300 GeV until the LHC is in shape. The same effect could enable the LHC running even at 7 TeV center of mass energy to scan Higgs masses between 200 and 300 GeV only with a few hundred pb^?1 of integrated luminosity.     

The hadronic tau decay signature of a heavy charged Higgs boson at LHC

The hadronic tau decay channel offers by far the best signature for heavy charged Higgs boson search at the LHC in the large tanβ region. By exploiting the distinct polarization of the tau and its large transverse mass, along with the accompanying missing–p_T, one can probe for a charged Higgs boson up to a mass of about 600 GeV in an essentially background-free environment. The transverse mass distribution of the tau jet also provides a fairly unambiguous estimate of the charged Higgs boson mass.     

The standard model process e^ + e^ - \to \nu \bar \nu b\bar b and its Higgs signal at LEP II

We present and study the results for the standard model process $e^ + e^ - \to \nu \bar \nu b\bar b$ at c.m. energies 150 ≤ √s(GeV) ≤ 240 and for Higgs boson masses 60 GeV ≤ m _H ≤ 110 GeV, obtained from all tree-level diagrams and including the most important radiative corrections. The matrix elements have been calculated by the ‘spinor bracket’ method without neglecting masses, which is presented in detail. The √s-dependence and the interference properties of the Higgs boson contributions and of various coherent background contributions to the total cross section are examined and compared. The important differential distributions for the Higgs boson and the background components are studied, providing information useful for choosing cuts in Higgs searches. We also examine the effect of a minimal set of cuts and evaluate the importance of the WW fusion for detecting a higher mass Higgs boson at LEP II.     

Search for the Higgs boson in the H→WW(*)→ℓ(+)νℓ(-)ν decay channel in pp collisions at √s=7 TeV with the ATLAS detector

A search for the Higgs boson has been performed in the H→WW(*)→?(+)ν?(-)ν[over ˉ] channel (?=e/μ) with an integrated luminosity of 2.05 fb(-1) of pp collisions at √s=7 TeV collected with the ATLAS detector at the Large Hadron Collider. No significant excess of events over the expected background is observed and limits on the Higgs boson production cross section are derived for a Higgs boson mass in the range 110 GeV相似文献   

Non-anomalous discrete R-symmetry, extra matters, and enhancement of the lightest SUSY Higgs mass

We consider low-energy supersymmetric model with non-anomalous discrete R-symmetry. To make the R-symmetry non-anomalous, we add new particles to the particle content of the minimal supersymmetric standard model (MSSM). Those new particles may couple to the Higgs boson, resulting in a significant enhancement of the lightest Higgs mass. We show that, in such a model, the lightest Higgs mass can be much larger than the MSSM upper bound; the lightest Higgs mass as large as 140 GeV (or larger) becomes possible.     

Search for the standard model Higgs boson in the decay channel H→ZZ→4ℓ in pp collisions at √s=7 TeV

A search for a Higgs boson in the four-lepton decay channel H→ZZ, with each Z boson decaying to an electron or muon pair, is reported. The search covers Higgs boson mass hypotheses in the range of 110100 GeV (with 13 below 160 GeV), while 67.1±6.0 (9.5±1.3) events are expected from background. The four-lepton mass distribution is consistent with the expectation of standard model background production of ZZ pairs. Upper limits at 95% confidence level exclude the standard model Higgs boson in the ranges of 134-158 GeV, 180-305 GeV, and 340-465 GeV. Small excesses of events are observed around masses of 119, 126, and 320 GeV, making the observed limits weaker than expected in the absence of a signal.     

Review of searches for Higgs bosons and beyond the Standard Model Physics at the Tevatron

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 DØ 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.     

Search for Higgs Bosons at LEP2 and Hadron Colliders

The search for the Higgs boson was one of the most relevant issues of the final years of LEP running at high energies. An excess of 3σ beyond the background expectation has been found, consistent with the production of the Higgs boson with a mass near 115 GeV/c². At the upgraded TeVatron and at LHC the search for the Higgs boson will continue. At TeVatron Higgs bosons can be detected with masses up to 180 GeV with an assumed total integrated luminosity of 20 fb^—1. LHC has the potential to discover the Higgs boson in many different decay channels for Higgs masses up to 1 TeV. It will be possible to measure Higgs boson parameters, such as mass, width, and couplings to fermions and bosons. The results from Higgs searches at LEP2 and the possibilities for searches at hadron colliders will be reviewed.     

Confronting the MSSM and the NMSSM with the discovery of a signal in the two photon channel at the LHC

We confront the discovery of a boson decaying into two photons, as reported recently by ATLAS and CMS, with the corresponding predictions in the Minimal Supersymmetric Standard Model (MSSM) and the Next-to-Minimal Supersymmetric Standard Model (NMSSM). We perform a scan over the relevant regions of parameter space in both models and evaluate the MSSM and NMSSM predictions for the dominant Higgs production channel and the photon–photon decay channel. Taking into account the experimental constraints from previous direct searches, flavor physics, electroweak measurements as well as theoretical considerations, we find that a Higgs signal in the two photon channel with a rate equal to, or above, the SM prediction is viable over the full mass range 123?M _H ?127 GeV, both in the MSSM and the NMSSM. We find that besides the interpretation of a possible signal at about 125 GeV in terms of the lightest $\mathcal {CP}$ -even Higgs boson, both the MSSM and the NMSSM permit also a viable interpretation where an observed state at about 125 GeV would correspond to the second-lightest $\mathcal {CP}$ -even Higgs boson in the spectrum, which would be accompanied by another light Higgs with suppressed couplings to W and Z bosons. We find that a significant enhancement of the γγ rate, compatible with the signal strengths observed by ATLAS and CMS, is possible in both the MSSM and the NMSSM, and we analyse in detail different mechanisms in the two models that can give rise to such an enhancement. We briefly discuss also our predictions in the two models for the production and subsequent decay into two photons of a $\mathcal {CP}$ -odd Higgs boson.     

Searches for invisibly decaying Higgs bosonswith the DELPHI detector at LEP

Searches for H Z production with the Higgs boson decaying into an invisible final state were performed using the data collected by the DELPHI experiment at centre-of-mass energies between 188 GeV and 209 GeV. Both hadronic and leptonic final states of the Z boson were analysed. In addition to the search for a heavy Higgs boson, a dedicated search for a light Higgs boson down to 40 GeV/c² was performed. No signal was found. Assuming the Standard Model HZ production cross-section, the mass limit for invisibly decaying Higgs bosons is 112.1 GeV/c² at 95% confidence level. An interpretation in the Minimal Supersymmetric extension of the Standard Model (MSSM) and in a Majoron model is also given.Received: 2 September 2003, Revised: 10 November 2003, Published online: 15 January 2004     

t\bar{t}H\to t\bar{t}\tau^{+}\tau^{-} —toward the measurement of the top-Yukawa coupling

One of the main goals of the ATLAS experiment is to measure various Higgs boson couplings as accurately as possible. Such a measurement is mandatory for a full understanding of the Higgs sector. One of the most challenging measurements of the Higgs boson properties is the determination of the Yukawa coupling to the top quark. To complement the $t\bar {t}H\rightarrow t\bar {t}\ensuremath {\mathit {b}\bar {\mathit {b}}}$ channel, which is the most significant in the low Higgs mass region (m _H ～120 GeV), we introduce a feasibility study of the $t\bar {t}H$ channel with the Higgs decaying to a pair of τ leptons. The signal events were reconstructed using the full and the fast simulation of the ATLAS detector. It is shown that both the distributions and the number of expected events after the same cuts agree, and that we can use the fast simulation to complete the analysis. We obtain a significance of 1.6σ for the low luminosity condition (30 fb^?1) and m _H =120 GeV, and 2.0σ for the high luminosity condition (300 fb^?1) and m _H =120 GeV. The observability of Higgs boson in this channel is demonstrated to be very marginal, even in the absence of taking into account $t\bar {t}+\mathrm{jets}$ .     

Do B meson decays exclude a light Higgs?

In the standard model with three generations a light Higgs boson will be produced in a quarter of all B meson decays. A novel calculation of the b → sH matrix element is given. Existing data on B meson decays excludes a light Higgs with mass less than 300 MeV or between 2 and 3.7 GeV. Because of theoretical uncertainties in the branching fractions for Higgs production and decay, a window between 300 MeV and 2 GeV is still allowed. Such a Higgs could be discovered at the ϒ (4S) in inclusive π⁺π⁻ or K⁺ K⁻ invariant mass plots, and in events with six kaons.     

The higgs boson mass in standard electroweak theory

The Higgs—boson mass in standardSU(2)×U(1) electroweak theory is obtained by requiring the one-loop effective potential to be an exact solution of the renormalization—group equation. Neglecting fermion couplings one getsm _H =35 GeV.     

Prospects for the measurement of the Higgs boson masswith a linear <Emphasis Type="Italic">e</Emphasis><Superscript> + </Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>-</Superscript> collider

The potential of a linear e ⁺ e^- collider operated at a centre-of-mass energy of 350 GeV is studied for the measurement of the Higgs boson mass. An integrated luminosity of 500 fb^-1 is assumed. For Higgs boson masses of 120, 150 and 180 GeV the uncertainty on the Higgs boson mass measurement is estimated to be 40, 65 and 70 MeV, respectively. The effects of beam related systematics, namely a bias in the beam energy measurement, the beam energy spread and the luminosity spectrum due to beamstrahlung, on the precision of the Higgs boson mass measurement are investigated. In order to keep the systematic uncertainty on the Higgs boson mass well below the level of the statistical error, the beam energy measurement must be controlled with a relative precision better than 10^-4. Received: 30 May 2005, Revised: 6 July 2005, Published online: 6 October 2005