Higgs Boson Mass

Top PDF Higgs Boson Mass:

An Upper Bound on the Higgs Self Coupling and Higgs Boson Mass from the Positivity Condition of the Mass Matrix

An Upper Bound on the Higgs Self Coupling and Higgs Boson Mass from the Positivity Condition of the Mass Matrix

Higgs boson is one of the main goals of present and future high energy colliders. On the one hand, the experi- mental verification of the Standard Model cannot be considered complete until the structure of the Higgs sector is not established by experiment. On the other hand, the Higgs is directly related to most of the major open prob- lems of particle physics, like the flavour problem or the hierarchy problem, the latter strongly suggesting the need for new physics near the weak scale, which can also clarify the dark matter identity. The detection of the Higgs particle [2] is extremely important for the understanding of the fundamental interactions among the quarks and leptons, as well as the generation of masses of fundamental particles given by spontaneous symmetry breaking. In the Standard Model the properties of the Higgs particle are uniquely determined, once its mass is fixed. Un- fortunately, the Higgs boson mass is a free parameter of the theory. The Higgs boson has been searched at LEP 2, and its mass should be greater than 114 GeV. On 4 July 2012, the ATLAS and CMS experiments at CERN’s LHC announced that they had each observed a new particle in the mass region around 125 to 126 GeV. This particle is consistent with the Higgs boson, but it will take further work to determine whether or not it is the Higgs boson predicted by the Standard Model. So, there is still a scope for a renewed interest in the evaluation of Higgs mass until the Standard Model Higgs is confirmed in the LHC experiment.
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Measurement of the Higgs boson mass with the ATLAS detector

Measurement of the Higgs boson mass with the ATLAS detector

An improved calibration scheme based on a multivariate regression algorithm was developed for precision measurements of electron and photon energy from data and simulation, as described in reference [6]. In addition, other studies were made: an intercalibration of the longitudinal layers of the calorimeter was performed from data, a measurement of the detector material achieving an improved simulation, a simulation-based calibration and a measurement of the energy scale from Z boson decays. Independent checks were performed using J/Ψ → e + e − and Z → l + l − γ samples (l = e, μ). These studies were based on the √ s = 7 and √ s = 8 TeV data.
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The Light CP-Even Higgs Boson Mass of the MSSM at Three-Loop Accuracy

The Light CP-Even Higgs Boson Mass of the MSSM at Three-Loop Accuracy

The analysis of convergence and the numerical evaluation of the integrals which are unknown analytically was performed with the help of the program TVID developed by A. Freitas [21]. TVID uses the discontinuities coming from the one-loop self-energy and the one-loop ver- tex in four dimensions to produce dispersion relations that are useful in the evaluation of the three-loop vacuum integrals in terms of one- and two-dimensional integral representa- tions. In all cases we have been able to get analytical expressions for the divergent part of the master integrals while the finite part could be numerically evaluated with up to 10 digits of accuracy. It is possible to reach this precision because the numerical integrations are at most 2-dimensional and therefore there is a controlled treatment of any singularities. It is also necessary an additional sub-renormalization procedure due to the presence of non-local divergences in the unrenormalized Higgs self-energies as well as in the Higgs tadpoles. As a consequence, we have to include also diagrams with counter-term insertions in order to remove sub-divergences. At three-loop level we need the renormalization of the gluino mass, the squark masses, the stop mixing angle and the top quark mass at the one-loop order. In addition we need the two-loop counterterms for the stop mixing angle, the stop quark masses and the top quark mass. The necessary expressions for these counterterms can be consulted in the review [22] and references therein.
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Searches for invisible decays of the Higgs boson in pp collisions at √s = 7, 8, and 13 TeV

Searches for invisible decays of the Higgs boson in pp collisions at √s = 7, 8, and 13 TeV

the Higgs boson in the ggH process is reweighted to match the NNLO plus next-to-next- to-leading-logarithmic (NNLL) prediction from HRes2.1 [48, 49]. The event generation at 13 TeV is tuned so that the p T distribution agrees between powheg 2.0 and HRes 2.1. Associated VH production is generated using pythia 6.4 ( pythia 8.1) at 7 and 8 (13) TeV and normalised to an inclusive cross section calculated at NNLO QCD and NLO EW precision [47]. The expected contribution from gg → ZH production is estimated using events generated with powheg 2.0 interfaced with pythia 8.1. All signal processes are generated assuming a Higgs boson mass of 125 GeV, consistent with the combined ATLAS and CMS measurement of the Higgs boson mass [50]. The SM Higgs boson cross sections at 125 GeV and their uncertainties for all production mechanisms are taken from ref. [51] at all centre-of-mass energies. A summary of the simulation used for the different signal processes is given in table 1.
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SUSY after LHC8: a brief overview

SUSY after LHC8: a brief overview

On top of this, also the results on the Higgs mass are relevant for our considerations. It is well known that in minimal SUSY models the tree level Higgs boson mass is bounded from above by the Z mass, so that large radia- tive correction are needed to increase the physical mass up to the observed value. The most relevant corrections are given by stops, i.e. exactly the same particles rele- vant for naturalness. In particular, it turns out that stops in the multi-TeV range and / or large stop mixing is needed to achieve a 125 GeV Higgs boson. This has to be compared with Eq. (5): the immediate consequence is that we expect [14]
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Higgs Boson search at the CMS experiment

Higgs Boson search at the CMS experiment

For a given Higgs boson mass hypothesis, the search sensitivity depends on the Higgs boson produc- tion cross section and decay branching fraction into the chosen final state, the signal selection effi- ciency, the Higgs boson mass resolution, and the level of standard model backgrounds with the same or a similar final state. In the low-mass range, the b b ¯ and ττ decay modes suffer from large back- grounds, which reduces the search sensitivity in these channels. For a low mass Higgs boson around 120 GeV, the best sensitivity is achieved in the γγ decay mode, which has a very small branching fraction, but manageable background. In the mass range 120-200 GeV, the best sensitivity is achieved in the H → WW channel. At higher masses, the H → ZZ branching fraction is large and the searches for H → ZZ → 4 and H → ZZ → 2 2 ν provide the best sensitivity. Among all decay modes, the H → γγ and H → ZZ → 4 channels play a special role as they provide an excellent mass resolu- tion for the reconstructed diphoton and four-lepton final states, respectively. A search for the Stan- dard Model Higgs boson is performed in the decay channels H→ γγ [6, 7], H→ ττ [9], H→b b ¯ [11], H→WW [14] and H→ZZ [12, 13] covering the mass range of 110 to 600 GeV. A combined result [18] of all the search channels considered using the CLs method [15–17] has also been presented.
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BEH Boson properties from CMS results

BEH Boson properties from CMS results

The legacy of LEP and SLC SM precision measurements [9], and of LEP, Tevatron and LHC direct searches for the H boson is contained in Fig. 1. In the SM, several physical observables can be predicted by calculating the effect of radiative corrections that depend on the Higgs boson mass. The ∆χ 2 as obtained from the SM fit to the precision measurements is superimposed to the regions excluded by direct searches. It is evident that the fit prefers a low value for the Higgs boson mass. In addition, only a very narrow window in the mass range remained not excluded by direct searches.
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Search for a high mass Higgs boson using the ATLAS detector

Search for a high mass Higgs boson using the ATLAS detector

A search for the SM Higgs boson in the mass range between 200 and 600 GeV has been performed in the H → ZZ → 2 l 2 ν (where l represents electrons or a muons) channel using 4.7 fb −1 of proton proton collision data recorded at a centre-of-mass energy of 7 TeV [26]. This channel is characterized by a final state with a large missing energy coming from the two neutrinos. The missing transverse momentum resolution is affected by the level of pile-up, resulting in a significant change in the signal to background ratio between low and high pile-up data taking periods. To retain the best sensitivity, the search is therefore split between the earlier “low pile-up data” (2.3 fb −1 ) and the later “high pile-up data” (2.4 fb −1 ) periods. In order to further increase the sensitivity, the search is also subdivided into a low Higgs boson mass region (m H < 280 GeV) and a high one (m H ≥ 280 GeV) where dedicated
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Final results of the searches for neutral Higgs bosons in e+e- collisions at sqrt(s) up to 209GeV

Final results of the searches for neutral Higgs bosons in e+e- collisions at sqrt(s) up to 209GeV

The reprocessing can change by small amounts the value of measured event properties such as the reconstructed Higgs boson mass or the b-tagging probabilities. Events close to some of the selection cuts may therefore move into or out of the selected sample. About 95% of the data events selected previously were also selected after the final processing. More specifically, the most signal-like events, i.e., those with a large contribution to the log-likelihood ratio − 2 ln Q, are still selected after the final processing.

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Broken Symmetries and the Higgs Boson

Broken Symmetries and the Higgs Boson

Abstract. The 40 years old Standard Model, the theory of particle physics, seems to de- scribe all experimental data very well. The theory is based on symmetries, some of them are broken, mostly by the weak interaction. All of its elementary particles were identi- fied and studied apart from the Higgs boson until 2012, when the two main experiments of the Large Hadron Collider at CERN, CMS and ATLAS observed a new particle with properties close to those predicted for the Higgs boson. The discovery of the Higgs bo- son proves the validity of the Brout-Englert-Higgs mechanism of spontaneous symmetry breaking and François Englert and Peter Higgs received the 2013 Nobel Prize in Physics. There are several questions yet concerning the possible theoretical significance of the mass of the new particle.
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The Physics of the Higgs-like Boson

The Physics of the Higgs-like Boson

The recently discovered boson could be a first experimen- tal signal of a new strongly-interacting sector: the light- est state of a large variety of new resonances of di ff er- ent types as happens in QCD. Among the many possibil- ities (technicolour, walking technicolour, conformal tech- nicolour, higher dimensions . . . ), the relatively light mass of the discovered Higgs candidate has boosted the interest on strongly-coupled scenarios with a composite pseudo- Goldstone Higgs boson [26], where the Higgs mass is pro- tected by an approximate global symmetry and is only generated via quantum e ff ects. A simple example is pro- vided by the popular SO(5)/SO(4) minimal composite Higgs model [27, 28]. Another possibility would be to interpret the Higgs-like scalar as a dilaton, the pseudo- Goldstone boson associated with the spontaneous break- ing of scale invariance at some scale f ϕ v [29–32].
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Ruckert, Benjamin
  

(2009):


	Search for a Higgs Boson Produced in Association with a W Boson at ATLAS.


Dissertation, LMU München: Fakultät für Physik

Ruckert, Benjamin (2009): Search for a Higgs Boson Produced in Association with a W Boson at ATLAS. Dissertation, LMU München: Fakultät für Physik

Using the jet with the highest transverse energy, with each additional jet an invariant mass can be calculated. This mass resembles that of the W boson, at least for the signal process. For the t t ¯ process there is a higher number of jets available and also more combinations, which leads to a slightly wider shape of the reconstructed mass. Regarding the W Z background, the distribution is much broader. The reason is due to the leptonic decay of both bosons, which goes along with the absence of hard jets. In that case, only jets from initial or final state radiation are used for the reconstruction. For all jets the invariant mass with the smallest deviation from the true mass of the W boson is taken, shown in fig. 6.4. There will always be a combination, but as it can be quite different from the real W mass, the distribution is broadened. The following cut window has been chosen
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Discovery of the Higgs Boson, Measurements of its Production, and a Search for Higgs Boson Pair Production

Discovery of the Higgs Boson, Measurements of its Production, and a Search for Higgs Boson Pair Production

The new particle interacts as the Higgs boson; beyond all reasonable doubt, it is a Higgs boson – and one remarkably similar to that predicted by the SM. Differential cross sections measurements are a natural next step: they cast a broad net for deviations from SM expectations that might hint at new physics in the Higgs sector; failing any exciting hints, they nevertheless begin to confront (sometimes very-advanced) calculations with (admittedly, statistics-limited) reality. The measure- ments are also natural from an experimental perspective. Most of the techniques and inputs can simply be ‘recycled’ from the baseline and ‘couplings’ analyses. Yields are extracted in bins of each physical observable using simultaneous fits of the signal plus background; these yields are unfolded to the actual production cross-sections (called particle-level, or truth-level throughout) using simple correction factors.
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Breakdown of QCD factorization in hard diffraction

Breakdown of QCD factorization in hard diffraction

Diffractive higgsstrahlung is possible due to a double-step process, via heavy quark production. Therefore, the main contribution comes for Higgs production in association with a heavy quark pair. Another important contribution to diffractive Higgs production comes from coalescence of intrinsic heavy quarks in the proton. For M H = 125 GeV dominance of intrinsic bottom and top is expected.

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Fermiophobic Higgs boson and supersymmetry

Fermiophobic Higgs boson and supersymmetry

LHC. We show that the predictions for the one-loop Higgs boson branching fractions and production rates in γγ and Z γ can be sizably modified with respect to the FP SM model, allowing a better fit to after Moriond collider data. However, the tree-level Higgs decay channels into WW ∗ and ZZ ∗ remain unaffected if the mixing between the singlet and doublet Higgs fields is absent. Relaxing this last condition, and so adding a new free parameter, the Higgs coupling to weak gauge boson WW and ZZ can be modified, and a suppression of the rates for h → WW ∗ and h → ZZ ∗ with respect to the pure FP model expectations can be achieved.
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Measurements of properties of the Higgs-like boson in the H → ZZ(*) → 4ℓ decay channel using the ATLAS detector

Measurements of properties of the Higgs-like boson in the H → ZZ(*) → 4ℓ decay channel using the ATLAS detector

The Z+jets production is modelled using A lpgen [21] and is divided into two sources: Z+light jets, which includes Zc¯ c in the massless c-quark approximation and Zb b ¯ with b b ¯ from parton showers, and Zb b ¯ using matrix element calculations that take into account the b-quark mass. The t t ¯ background is modelled using MC@NLO [22] and is normalised to the approximate NNLO cross section calculated using H athor [23]. Both A lpgen and MC@NLO are interfaced to H erwig [24] for parton shower hadronization and to J immy [25] for the underlying event simulation.

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Search for the standard model Higgs boson decaying to two photons with CMS at the LHC

Search for the standard model Higgs boson decaying to two photons with CMS at the LHC

Figure 4 shows the 95% CL exclusion limits combined for the 7 and 8 TeV data samples. The Higgs boson exclu- sion was expected in the mass range between 110 and 143 GeV. The observed limit shows the presence of a large ex- cess at about 125 GeV and excludes the Higgs boson at 95% CL in the three mass ranges 114 to 121 GeV, 129 to 132 GeV and 138 to 149 GeV. The corresponding local p- values observed are shown in Fig. 5; the minimum, corre- sponding to the largest upward fluctuation of the observed limit, falls at about 125 GeV, with a value of 1.8 × 10 −5 corresponding to 4.1σ local significance. The global sig- nificance in the whole mass range 110 to 150 GeV is 3.5 σ. This result is consistent with the observation of a new boson with mass ∼ 125 GeV.
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Hadron Collider Physics Symposium - Contents

Hadron Collider Physics Symposium - Contents

12062 Search for Standard Model Higgs boson in the four-lepton channel with. ATLAS[r]

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SUSY vs LHC

SUSY vs LHC

which is equivalent to estimate without the log divergence. The same is true for the e ff ect of the stop mass to the Higgs mass parameters. One can consider a more drastic change of the theory such as the appearance of an extra dimension at a scale Λ . See Ref. [14] for a proposal to obtain com- posite Higgs fields couple to the U(2) model above from a higher dimensional QCD.

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Measurement of the Higgs boson coupling properties in the H -> ZZ* -> 4l decay channel at root s=13 TeV with the ATLAS detector

Measurement of the Higgs boson coupling properties in the H -> ZZ* -> 4l decay channel at root s=13 TeV with the ATLAS detector

The production of the SM Higgs boson via ggF, VBF and VH (including gg → ZH) pro- duction mechanisms was modelled with the POWHEG-BOX v2 Monte Carlo (MC) event generator [23, 24], interfaced to EvtGen v1.2.0 [25] for properties of the bottom and charm hadron decays, using the PDF4LHC next-to-leading-order (NLO) set of parton distribution functions (PDF) [26]. The gluon-gluon fusion Higgs boson production is accurate to next- to-next-to-leading order (NNLO) in the strong coupling, using the POWHEG method for merging the NLO Higgs + jet cross section with the parton shower, and the MiNLO method [27] to simultaneously achieve NLO accuracy for inclusive Higgs boson produc- tion. A reweighting procedure, employing the Higgs boson rapidity, was applied using the HNNLO program [28, 29]. The matrix elements of the VBF and VH production mecha- nisms were calculated up to NLO in QCD. For VH production, the MiNLO method was used to merge 0- and 1-jet events [30]. The gg → ZH contribution was modelled at leading order (LO) in QCD. The production of a Higgs boson in association with a top (bottom) quark pair was simulated at NLO with MadGraph5 aMC@NLO v2.2.3 (v2.3.3) [31, 32], using the CT10nlo PDF set [33] for ttH production and the NNPDF23 PDF set [34] for bbH production. For the ggF, VBF, VH and bbH production mechanisms, the PYTHIA 8 [35] generator was used for the H → ZZ ∗ → 4ℓ decay as well as for the parton shower model
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