Higgs Boson Mass Mh Research Articles

The Electroweak Phase Transition in a Spontaneously Magnetized Plasma

We investigate the electroweak phase transition (EWPT) in the Minimal (One Higgs doublet) Standard Model (SM) with account for the spontaneous generation of magnetic and chromo-magnetic fields. As it is known, in the SM for the mass of a Higgs boson greater than 75 GeV, this phase transition is of the second order. But, according to Sakharov’s conditions for the formation of the baryon asymmetry in the early Universe, it has to be strongly of the first order. In the Two Higgs doublets SM, there is a parametric space, where the first-order phase transition is realized for the realistic Higgs boson mass mH = 125 GeV. On the other hand, in the hot Universe, the spontaneous magnetization of a plasma had happened. The spontaneously generated (chromo) magnetic fields are temperature-dependent. They influence the EWРT. The color chromomagnetic fields B3 and B8 are created spontaneously in the gluon sector of QCD at a temperature T > Td higher the deconfinement temperature Td. The usual magnetic field H has also to be spontaneously generated. For T close to the TEWPT , these magnetic fields could change the kind of the phase transition.

Next-to-leading order QCD and electroweak corrections to Higgs-strahlung processes at the LHC**Supported by the National Natural Science Foundation of China (11465018)

In this paper we calculate the total and fiducial cross sections as well as differential distributions for the Higgs-strahlung or VH process pp → VH → lνl/l− l+ + H, (V = W or Z, l = e, μ) including QCD and electro-weak corrections up to next-to-leading order before and after reweighting photon PDFs of NNPDF2.3qed, NNPDF3.0qed, MRST2004qed, CT14QEDinc, and LUXqed at the LHC with 13 TeV and Higgs boson mass MH = 125 GeV. The predictions from the various photon PDFs before and after reweighting against each other are in good agreement. The photon PDF uncertainties of the photon-induced cross sections decrease significantly with the reweighting PDFs.

Minimal supersymmetry confronts Rb, and mh

We study the impact of the measurements of three sets of observables on the parameter space of the constrained minimal supersymmetric standard model (cMSSM), its slightly general variant, the non-universal scalar model (NUSM), and some selected benchmark points of the 19-parameter phenomenological MSSM (pMSSM): (i) the direct measurement of the Higgs boson mass mh ≈ 125 GeV at the CERN Large Hadron Collider (LHC); (ii) Z-boson decay width in the channel normalized to its hadronic width (Rb), and the forward–backward asymmetry on the Z-peak in the same channel ; and (iii) several B-physics observables, along with (g − 2) of muon. In addition, there are constraints from non-observation of superparticles from direct searches at the LHC. In view of the recently re-estimated standard model (SM) value of Rb with improved higher order corrections, the measured value of Rb has a 1.2σ discrepancy with its SM value, while the corresponding discrepancy in is 2.5σ. MSSM contributions from light superpartners improve the agreement of Rb but worsen that of . We project this (Rb–) tension vis-à-vis the constraints arising from other observables in the parameter space of cMSSM and NUSM. We also consider a few well-motivated pMSSM benchmark points and show that pMSSM does not fare any better than the SM.

Higgs boson and top-quark masses and parity-symmetry restoration

The recent ATLAS and CMS experiments show the first observations of a new particle in the search for the Standard Model Higgs boson at the LHC. We revisit the scenario that high-dimensional operators of fermions must be present due to the theoretical inconsistency of the fundamental cutoff (quantum gravity) with the parity-violating gauge symmetry of the Standard Model. Studying the four-fermion interaction of the third quark family, we show that at an intermediate energy threshold E≈4.27×103GeV for the four-fermion coupling being larger than a critical value, the spontaneous symmetry-breaking phase transits to the strong-coupling symmetric phase where composite Dirac fermions form fully preserving the chiral gauge symmetry of the Standard Model and the parity-symmetry is restored. Under this circumstance, we perform the standard analysis of renormalization-group equations of the Standard Model in the spontaneous symmetry-breaking phase. As a result, the Higgs boson mass mH≈126.7GeV and top-quark mass mt≈172.7GeV are obtained without drastically fine-tuning the four-fermion coupling.

Experimental and theoretical uncertainties in top-quark mass measurements at the Tevatron and the LHC

Since the discovery of the top-quark at the Tevatron collider in 1995, enormous efforts have been devoted to the precise determination of its properties and in particular of its mass, mtop. Together with precision electroweak measurements, mtop can be used to check the Higgs boson mass (mH) dependencies on mtop and the W boson mass (mW) within the Standard Model, and to constrain the allowed mass range for heavy particles predicted by Standard Model extensions. In this paper a review of the current experimental and theoretical uncertainties affecting the top-quark mass measurements at the Tevatron and the LHC is provided: strategies and techniques adopted to evaluate the main systematic uncertainties within the various experiments are summarised and compared, highlighting, when appropriate, complementarities and differences which are important ingredients to set the basis of a future world mtop combination.

On the difference between the pole and the [formula omitted] masses of the top quark at the electroweak scale

We argue that for a Higgs boson mass MH∼125 GeV, as suggested by recent Higgs searches at the LHC, the inclusion of electroweak radiative corrections in the relationship between the pole and MS¯ masses of the top quark reduces the difference to about 1 GeV. This is relevant for the scheme dependence of electroweak observables, such as the ρ parameter, as well as for the extraction of the top quark mass from experimental data. In fact, the value currently extracted by reconstructing the invariant mass of the top quark decay products is expected to be close to the pole mass, while the analysis of the total cross section of top quark pair production yields a clean determination of the MS¯ mass.

Novel universality and Higgs decay [formula omitted] in the [formula omitted] gauge-Higgs unification

The SO(5)×U(1) gauge-Higgs unification in the Randall–Sundrum warped space with the Higgs boson mass mH=126 GeV is constructed. A universal relation is found between the Kaluza–Klein (KK) mass scale mKK and the Aharonov–Bohm (AB) phase θH in the fifth dimension; mKK∼1350GeV/(sinθH)0.787. The cubic and quartic self-couplings of the Higgs boson become smaller than those in the standard model (SM), having universal dependence on θH. The decay rates H→γγ,gg are evaluated by summing contributions from KK towers. Corrections coming from KK excited states are finite and about 0.2% (2%) for θH=0.12(0.36), branching fractions of various decay modes of the Higgs boson remaining nearly the same as in the SM. The signal strengths of the Higgs decay modes relative to the SM are ∼cos2θH. The mass of the first KK Z is predicted to be 5.9(2.4) TeV for θH=0.12(0.36). We also point out the possible enhancement of Γ(H→γγ) due to the large U(1)X charge of new fermion multiplets.

Search for the Standard Model Higgs boson in the decay channel H → ZZ (*) → 4l at CMS

A search for the Standard Model (SM) Higgs boson in the decay channel H → ZZ( ∗ ) → 4l with each Z boson decaying to an electron or muon pair is presented using pp collisions from the LHC at \(\sqrt s = 7\) TeV. The data analysed correspond to an integrated luminosity of 1.66 ±0.07 fb − 1 recorded by the CMS detector in 2010 and 2011. The search covers Higgs boson mass (mH) hypotheses of \(110 < m_{\rm H} < 600~{\rm GeV/c^{2}}\). Twenty-one events are observed, while 21.2 ±0.8 events are expected from Standard Model (SM) background processes. The events are not clustered in mass excluding interpretation as the SM Higgs boson and its (4l) mass distribution is consistent with the expectation of SM continuum production of ZZ( ∗ ) pairs. Upper limits at 95% CL on the cross-section × branching ratio for a SM Higgs boson with SM like decays exclude cross-sections from about once to twice the expected SM cross-section for masses in the range of \(150< m_{\rm H} < 420~{\rm GeV/c^{2}}\).

A heavier gluino from t–b–τ Yukawa-unified SUSY

Supersymmetric models with t–b–τ Yukawa coupling unification and unified gaugino masses at the GUT scale—with μ>0—show a mild preference for light gluino masses mg˜≲500 GeV. This range of mg˜ is now essentially ruled out by LHC searches. We show that a heavier gluino with mg˜∼0.5–3 TeV can also be compatible with excellent t–b–τ Yukawa coupling unification in supersymmetric models with non-universal Higgs masses (NUHM2). The gluino in such models is the lightest colored sparticle, while the squark sector displays an inverted mass hierarchy with mq˜∼5–20 TeV. We present some LHC testable benchmark points for which the lightest Higgs boson mass mh≃125 GeV. We also discuss LHC signatures of Yukawa-unified models with heavier gluinos. We expect gluino pair production followed by decay to final states containing four b-jets plus four W-bosons plus missing ET to occur at possibly observable rates at LHC.

A Higgs mass shift to 125 GeV and a multi-jet supersymmetry signal: Miracle of the flippons at the [formula omitted] LHC

We describe a model named No-Scale F-SU(5) which is simultaneously capable of explaining the dual signals emerging at the LHC of (i) a 124–126 GeV Higgs boson mass mh, and (ii) tantalizing low-statistics excesses in the multi-jet data which may attributable to supersymmetry. These targets tend to be mutually exclusive in more conventional approaches. The unified mechanism responsible for both effects is the introduction of a rather unique set of vector-like multiplets at the TeV scale, dubbed flippons, which (i) can elevate mh by around 3–4 GeV via radiative loop corrections, and (ii) flatten the running of the strong coupling and color-charged gaugino, resulting in a prominent collider signal from production of light gluino pairs. This well-motivated theoretical framework maintains consistency with all key phenomenological constraints, and all residual parameterization freedom may in principle be fixed by a combination of the two experiments described. We project that the already collected luminosity of 5 fb−1 may be sufficient to definitively establish the status of this model, given appropriate data selection cuts.

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.

Chiral symmetry breaking in three-dimensional QED with Abelian Higgs model

We study the dynamical chiral symmetry breaking in (2+1)-dimensional QED in the presence of an Abelian Higgs model (Ginzburg–Landau model) at the leading order of 1/N. In the gauge symmetry broken phase, the gauge boson becomes massive via the Anderson–Higgs mechanism. The Dyson–Schwinger equation for fermion self-energy depends on two parameters: the gauge boson mass mA and the Higgs boson mass mh. It is found that, in the region of large ratio r = mh/mA, mA and mh reduces the critical fermion number Nc, below which the massless fermion acquires a dynamical mass.

Search for a light standard model Higgs boson in the channel

A prospective analysis for the discovery of a light standard model Higgs boson in the CMS experiment at the large hadron collider is presented. The analysis focuses on the inclusive single production p + p → H + X and the Higgs boson decay channel , for a Higgs boson mass MH in the range 120 < MH < 160GeV/c2. A full simulation of the detector response is performed and detailed electron, jet and missing transverse energy reconstruction algorithms are used. Emphasis is put on a realistic treatment of background contamination and systematics. A Higgs boson of mass MH ≳ 134GeV/c2 would be observed with a significance above three standard deviations in the channel alone for an integrated LHC luminosity above 30 fb−1.

Higgs-mass dependence of the effective electroweak mixing angle [formula omitted] at the two-loop level

The result for the Higgs-dependent electroweak two-loop bosonic contributions to the effective leptonic mixing angle of the Z-boson in the Standard Model is presented. Together with the previously calculated fermionic contributions it yields the complete dependence of sin2θeff on the Higgs-boson mass MH. Compared to the fermionic contributions, the bosonic contributions are found to be smaller and have the opposite sign, compensating part of the fermionic contributions.

Higgs boson mass and electroweak–gravity hierarchy from dynamical gauge–Higgs unification in the warped spacetime

Dynamical electroweak symmetry breaking by the Hosotani mechanism in the Randall–Sundrum warped spacetime is examined, relations among the W-boson mass (mW), the Kaluza–Klein mass scale (MKK), and the Higgs boson mass (mH) being derived. It is shown that MKK/mW∼(2πkR)1/2(π/θW) and mH/mW∼0.058kR(π/θW), where k2, R, and θW are the curvature and size of the extra-dimensional space and the Wilson line phase determined dynamically. For typical values kR=12 and θW=(0.2–0.4)π, one finds that MKK=1.7–3.5 TeV, k=(1.3–2.6)×1019 GeV, and mH=140–280 GeV.

Full [formula omitted] electroweak corrections to e+e−→HHZ

We calculate the full O(αew) electroweak corrections to the Higgs pair production process e+e−→HHZ at an electron–positron linear collider in the standard model, and analyze the dependence of the Born cross section and the corrected cross section on the Higgs boson mass mH and the c.m. energy s. To see the origin of some of the large corrections clearly, we calculate the QED and genuine weak corrections separately. The numerical results show that the corrections significantly suppress or enhance the Born cross section, depending on the values of mH and s. For the c.m. energy s=500 GeV, which is the most favorable colliding energy for HHZ production with intermediate Higgs boson mass, the relative correction decreases from −5.3% to −11.5% as mH increases from 100 to 150 GeV. For the range of the c.m. energy where the cross section is relatively large, the genuine weak relative correction is small, less than 5%.

Electroweak radiative corrections to [formula omitted] at linear colliders

We calculate the O(αew) electroweak radiative corrections to e+e−→tt̄h at a electron–positron linear collider (LC) in the standard model. We analyze the dependence of the O(αew) corrections on the Higgs boson mass mh and colliding energy s, and find that the corrections significantly decrease or increase the Born cross section depending on the colliding energy. The numerical results show that the O(αew) relative correction is strongly related to the Higgs boson mass when s=500 GeV, and for mh=150 GeV the relative correction ranges from −31.3% to 2.3% as the increment of the colliding energy from 500 GeV to 2 TeV.

Higgs and top mass predictions in GUT models with fixed-point solutions

We study fixed-point solutions inSU(5) andSO(10) super-symmetric grand unified models. For theSU(5) model with a single largeht coupling constant we find 155GeV≤mt≤200 GeV. For 155GeV≤mt≤175GeV we find that the Higgs boson is lighter thanMZ. TheSU(5) andSU(10) fixed-point solutions with largeht andhb coupling constants give a top-quark massmh=180–190 GeV and a Higgs boson massmh=118–120 GeV (forMSUSY=1 TeV). From the requirement of the absence of a Landau pole singularity up to the Planck scale we find an upper bound on the top massmt≤209 GeV in theSU(5) model andmt≤193 GeV for theSO(10) model.

Implications of the top quark mass measurement for the SM Higgs boson mass MH

Motivated by the recent determination of the top quark mass by the CDF Collaboration Mt=174+or-10-12+13 GeV, we study,the implications of the top quark mass measurement for the standard model Higgs boson mass MH based on the phenomenological analysis of the radiative correction Delta r at two-loop order. We find that: (a) the central value of MH is very sensitive to the variation of Mt; (b) the present data are in favour of the heavy Higgs boson, MH=340-270+770 GeV for Mt=174 GeV, but no reliable constraints on MH could be derived until the measurement of Mt reaches high precision.

Upper Bounds on Top Quark Mass, Z Boson Decay Widths and Mass Ratio MW/MZ11The project supported by the Science Foundation of Henan Educational Committee.

In this paper we made a comprehensive analysis of some latest experimental data—the Z boson decay widths, the mass ratio MW/MZ and effective vector coupling constant gv, within the framework of standard model. We considered the , order QCD corrections in the calculation of Γh and ΓZ. The analysis shows that the mass ratio (Mt/MZ)2 is rather sensitive to the change of the strong coupling constant αs(MZ), and the smaller value αs(MZ) ≤ 0.128 is preferred. The upper bounds on top quark mass Mt are obtained from different analyses. The final averaged result is Mt = 102 ± 37 GeV, or Mt < 186 GeV at 95% C.L. for Higgs boson mass MH in the range of 50 ~ 1000 GeV.