Higgs Boson Production Rates Research Articles

XCC: an X-ray FEL-based γγ Compton collider Higgs factory

This report describes the conceptual design of a γγ Higgs factory in which 62.8 GeV electron beams collide with 1 keV X-ray free electron laser (XFEL) beams to produce colliding beams of 62.5 GeV photons. The Higgs boson production rate is 80,000 Higgs bosons per 107 second year, roughly the same as the ILC Higgs rate at √s = 250 GeV. The electron accelerator is based on cold copper distributed coupling (C3) accelerator technology. Unlike the center-of-mass energy spectra of previous optical wavelength γγ collider designs, the sharply peaked γγ center-of-mass energy spectrum of XCC produces model independent Higgs coupling measurements with precision on par with e + e - colliders. For the triple Higgs coupling measurement, the XCC center-of-mass energy can be upgraded to 380 GeV, where the cross section for γγ → HH is twice that of e + e - → ZHH at √s = 500 GeV. Design challenges are discussed, along with the R&D to address them, including demonstrators.

Measurements of Higgs boson production cross sections and couplings in the diphoton decay channel at sqrt{mathrm{s}} = 13 TeV

Measurements of Higgs boson production cross sections and couplings in events where the Higgs boson decays into a pair of photons are reported. Events are selected from a sample of proton-proton collisions at sqrt{s} = 13 TeV collected by the CMS detector at the LHC from 2016 to 2018, corresponding to an integrated luminosity of 137 fb−1. Analysis categories enriched in Higgs boson events produced via gluon fusion, vector boson fusion, vector boson associated production, and production associated with top quarks are constructed. The total Higgs boson signal strength, relative to the standard model (SM) prediction, is measured to be 1.12±0.09. Other properties of the Higgs boson are measured, including SM signal strength modifiers, production cross sections, and its couplings to other particles. These include the most precise measurements of gluon fusion and vector boson fusion Higgs boson production in several different kinematic regions, the first measurement of Higgs boson production in association with a top quark pair in five regions of the Higgs boson transverse momentum, and an upper limit on the rate of Higgs boson production in association with a single top quark. All results are found to be in agreement with the SM expectations.

Measurements of production cross sections of the Higgs boson in the four-lepton final state in proton\u2013proton collisions at sqrt{s} = 13,text {TeV}

Production cross sections of the Higgs boson are measured in the {mathrm{H}} rightarrow {mathrm{Z}} {mathrm{Z}} rightarrow 4ell (ell ={mathrm{e}},{{{upmu }}_{mathrm{}}^{mathrm{}}} ) decay channel. A data sample of proton–proton collisions at a center-of-mass energy of 13,text {TeV}, collected by the CMS detector at the LHC and corresponding to an integrated luminosity of 137,text {fb}^{-1} is used. The signal strength modifier mu , defined as the ratio of the Higgs boson production rate in the 4ell channel to the standard model (SM) expectation, is measured to be mu =0.94 pm 0.07 ,text {(stat)} ^{+0.09}_{-0.08} ,text {(syst)} at a fixed value of m_{{mathrm{H}}} = 125.38,text {GeV} . The signal strength modifiers for the individual Higgs boson production modes are also reported. The inclusive fiducial cross section for the {mathrm{H}} rightarrow 4ell process is measured to be 2.84^{+0.23}_{-0.22} ,text {(stat)} ^{+0.26}_{-0.21} ,text {(syst)} ,text {fb} , which is compatible with the SM prediction of 2.84 pm 0.15 ,text {fb} for the same fiducial region. Differential cross sections as a function of the transverse momentum and rapidity of the Higgs boson, the number of associated jets, and the transverse momentum of the leading associated jet are measured. A new set of cross section measurements in mutually exclusive categories targeted to identify production mechanisms and kinematical features of the events is presented. The results are in agreement with the SM predictions.

Measurement of the Higgs boson production rate in association with top quarks in final states with electrons, muons, and hadronically decaying tau leptons at sqrt{s} = 13,text {TeV}

The rate for Higgs ({mathrm{H}} ) bosons production in association with either one ({mathrm{t}} {mathrm{H}} ) or two ({mathrm{t}} {{overline{{{mathrm{t}}}}}} {mathrm{H}} ) top quarks is measured in final states containing multiple electrons, muons, or tau leptons decaying to hadrons and a neutrino, using proton–proton collisions recorded at a center-of-mass energy of 13,text {TeV} by the CMS experiment. The analyzed data correspond to an integrated luminosity of 137,text {fb}^{-1}. The analysis is aimed at events that contain {mathrm{H}} rightarrow {mathrm{W}} {mathrm{W}} , {mathrm{H}} rightarrow {uptau } {uptau } , or {mathrm{H}} rightarrow {mathrm{Z}} {mathrm{Z}} decays and each of the top quark(s) decays either to lepton+jets or all-jet channels. Sensitivity to signal is maximized by including ten signatures in the analysis, depending on the lepton multiplicity. The separation among {mathrm{t}} {mathrm{H}} , {mathrm{t}} {{overline{{{mathrm{t}}}}}} {mathrm{H}} , and the backgrounds is enhanced through machine-learning techniques and matrix-element methods. The measured production rates for the {mathrm{t}} {{overline{{{mathrm{t}}}}}} {mathrm{H}} and {mathrm{t}} {mathrm{H}} signals correspond to 0.92 pm 0.19,text {(stat)} ^{+0.17}_{-0.13},text {(syst)} and 5.7 pm 2.7,text {(stat)} pm 3.0,text {(syst)} of their respective standard model (SM) expectations. The corresponding observed (expected) significance amounts to 4.7 (5.2) standard deviations for {mathrm{t}} {{overline{{{mathrm{t}}}}}} {mathrm{H}} , and to 1.4 (0.3) for {mathrm{t}} {mathrm{H}} production. Assuming that the Higgs boson coupling to the tau lepton is equal in strength to its expectation in the SM, the coupling y_{{mathrm{t}}} of the Higgs boson to the top quark divided by its SM expectation, kappa _{{mathrm{t}}}=y_{{mathrm{t}}}/y_{{mathrm{t}}}^{mathrm {SM}}, is constrained to be within -0.9< kappa _{{mathrm{t}}}< -0.7 or 0.7< kappa _{{mathrm{t}}}< 1.1, at 95% confidence level. This result is the most sensitive measurement of the {mathrm{t}} {{overline{{{mathrm{t}}}}}} {mathrm{H}} production rate to date.

C P violation from \u03c4 , t and b dimension-6 Yukawa couplings \u2014 interplay of baryogenesis, EDM and Higgs physics

We explore the implications of the Standard Model effective field theory (SMEFT) with dimension-six terms involving the Higgs boson and third-generation fermion fields on the rate of Higgs boson production and decay into fermions, on the electric dipole moments (EDMs) of the electron, and on the baryon asymmetry of the Universe. We study the consequences of allowing these additional terms for each flavor separately and for combinations of two flavors. We find that a complex τ Yukawa coupling can account for the observed baryon asymmetry {Y}_B^{mathrm{obs}} within current LHC and EDM bounds. A complex b (t) Yukawa coupling can account for 4% (2%) of {Y}_B^{mathrm{obs}} , whereas a combination of the two can reach 12%. Combining τ with either t or b enlarges the viable parameter space owing to cancellations in the EDM and in either Higgs production times decay or the total Higgs width, respectively. Interestingly, in such a scenario there exists a region in parameter space where the SMEFT contributions to the electron EDM cancel and collider signal strengths are precisely SM-like, while producing sufficient baryon asymmetry. Measuring C P violation in Higgs decays to τ leptons is the smoking gun for this scenario.

Measurements of the Higgs boson production and decay rates and constraints on its couplings from a combined ATLAS and CMS analysis of the LHC pp collision data at s = 7 $$ \sqrt{s}=7 $$ and 8 TeV

Combined ATLAS and CMS measurements of the Higgs boson production and decay rates, as well as constraints on its couplings to vector bosons and fermions, are presented. The combination is based on the analysis of five production processes, namely gluon fusion, vector boson fusion, and associated production with a $W$ or a $Z$ boson or a pair of top quarks, and of the six decay modes $H \to ZZ, WW$, $\gamma\gamma, \tau\tau, bb$, and $\mu\mu$. All results are reported assuming a value of 125.09 GeV for the Higgs boson mass, the result of the combined measurement by the ATLAS and CMS experiments. The analysis uses the CERN LHC proton--proton collision data recorded by the ATLAS and CMS experiments in 2011 and 2012, corresponding to integrated luminosities per experiment of approximately 5 fb$^{-1}$ at $\sqrt{s}=7$ TeV and 20 fb$^{-1}$ at $\sqrt{s} = 8$ TeV. The Higgs boson production and decay rates measured by the two experiments are combined within the context of three generic parameterisations: two based on cross sections and branching fractions, and one on ratios of coupling modifiers. Several interpretations of the measurements with more model-dependent parameterisations are also given. The combined signal yield relative to the Standard Model prediction is measured to be 1.09 $\pm$ 0.11. The combined measurements lead to observed significances for the vector boson fusion production process and for the $H \to \tau\tau$ decay of $5.4$ and $5.5$ standard deviations, respectively. The data are consistent with the Standard Model predictions for all parameterisations considered.

Measurements of the Higgs boson production and decay rates and coupling strengths using pp collision data at [Formula: see text] and 8TeV in the ATLAS experiment.

Combined analyses of the Higgs boson production and decay rates as well as its coupling strengths to vector bosons and fermions are presented. The combinations include the results of the analyses of the Hrightarrow gamma gamma ,, ZZ^*,, WW^*,, Zgamma ,, bbar{b},, tau tau and mu mu decay modes, and the constraints on the associated production with a pair of top quarks and on the off-shell coupling strengths of the Higgs boson. The results are based on the LHC proton-proton collision datasets, with integrated luminosities of up to 4.7 mathrm {fb}^{-1} at sqrt{s}=7 TeV and 20.3 mathrm {fb}^{-1} at sqrt{s}=8 TeV, recorded by the ATLAS detector in 2011 and 2012. Combining all production modes and decay channels, the measured signal yield, normalised to the Standard Model expectation, is 1.18^{+0.15}_{-0.14}. The observed Higgs boson production and decay rates are interpreted in a leading-order coupling framework, exploring a wide range of benchmark coupling models both with and without assumptions on the Higgs boson width and on the Standard Model particle content in loop processes. The data are found to be compatible with the Standard Model expectations for a Higgs boson at a mass of 125.36 GeV for all models considered.

Stop-catalyzed baryogenesis beyond the MSSM

Non-minimal supersymmetric models that predict a tree-level Higgs mass above the Minimal Supersymmetric Standard Model (MSSM) bound are well motivated by naturalness considerations. Indirect constraints on the stop sector parameters of such models are significantly relaxed compared to the MSSM; in particular, both stops can have weak-scale masses. We revisit the stop-catalyzed electroweak baryogenesis (EWB) scenario in this context. We find that the LHC measurements of the Higgs boson production and decay rates already rule out the possibility of stop-catalyzed EWB. We also introduce a gauge-invariant analysis framework that may generalize to other scenarios in which interactions outside the gauge sector drive the electroweak phase transition.

Tevatron constraints on models of the Higgs boson with exotic spin and parity using decays to bottom-antibottom quark pairs.

Combined constraints from the CDF and D0 Collaborations on models of the Higgs boson with exotic spin J and parity P are presented and compared with results obtained assuming the standard model value JP=0+. Both collaborations analyzed approximately 10 fb(-) of proton-antiproton collisions with a center-of-mass energy of 1.96 TeV collected at the Fermilab Tevatron. Two models predicting exotic Higgs bosons with JP=0- and JP=2+ are tested. The kinematic properties of exotic Higgs boson production in association with a vector boson differ from those predicted for the standard model Higgs boson. Upper limits at the 95% credibility level on the production rates of the exotic Higgs bosons, expressed as fractions of the standard model Higgs boson production rate, are set at 0.36 for both the JP=0- hypothesis and the JP=2+ hypothesis. If the production rate times the branching ratio to a bottom-antibottom pair is the same as that predicted for the standard model Higgs boson, then the exotic bosons are excluded with significances of 5.0 standard deviations and 4.9 standard deviations for the JP=0- and JP=2+ hypotheses, respectively.

Higgs data confronts sequential fourth generation fermions in the Higgs triplet model

We investigate the effect of introducing a sequential generation of chiral fermions in the Higgs Triplet Model with nontrivial mixing between the doublet and triplet Higgs. We use the available LHC data for Higgs boson production and decay rates, the constraints on the fourth generation masses, and impose electroweak precision constraints from the S, T and U parameters. Our analysis shows that an SM-like Higgs boson state at ~125 GeV can be accommodated in the Higgs Triplet Model with four generations, and thus, that four generations survive collider and electroweak precision constraints in models beyond SM.

LHC diphoton and Z+photon Higgs signals in the Higgs triplet model with Y = 0

We study the implications of the LHC diphoton and Z+photon Higgs signals on the Higgs triplet model with Y=0. We discuss three different scenarios: (i) the observed boson is the light Higgs boson $h$; (ii) it is the heavy Higgs boson $H$; (iii) the observed signal is from the almost degenerate $h$ and $H$. We find that the inclusive Higgs diphoton rates in the first two scenarios can be enhanced or suppressed compared to the SM value, which can respectively fit the ATLAS and CMS diphoton data within $1\sigma$ range. The inclusive $ZZ^*$ rates are suppressed, which are outside $1\sigma$ range of ATLAS data and within $1\sigma$ range of CMS data. Meanwhile, another CP-even Higgs boson production rate can be suppressed enough not to be observed at the collider. For the third scenario, the Higgs diphoton rate is suppressed, which is outside $1\sigma$ range of ATLAS data, and the $ZZ^*$ rate equals to SM value approximately. In addition, we find that the two rates of $h\to \gamma\gamma$ and $h\to Z\gamma$ have the positive correlations for the three scenarios.

Search for Higgs boson production in trilepton and like-charge electron-muon final states with the D0 detector

We present a search for Higgs bosons in multilepton final states in pp-bar collisions at sqrt(s)=1.96 TeV recorded with the D0 detector at the Fermilab Tevatron Collider, using the full Run II data set with integrated luminosities of up to 9.7 fb-1. The multilepton states considered are two electron plus muon, electron with two muons, muon with two hadronic tau leptons, and like-charge electron-muon pairs. These channels directly probe the HVV (V=W,Z) coupling of the Higgs boson in production and decay. The muon with two hadronic tau lepton channel is also sensitive to H to tau lepton pair decays. Upper limits at the 95% C.L on the rate of standard model Higgs boson production are derived in the mass range 100 <= M_H <= 200 GeV. The expected and observed limits are a factor of 6.3 and 8.4 above the predicted standard model cross section at M_H=125 GeV. We also interpret the data in a fermiophobic Higgs boson model.

Observing Higgs boson production through its decay into γ-rays: A messenger for dark matter candidates

In this Letter, we study the γ-ray signatures subsequent to the production of a Higgs boson in space by dark matter annihilations. We investigate the cases where the Higgs boson is produced at rest or slightly boosted and show that such configurations can produce characteristic bumps in the γ-ray data. These results are relevant in the case of the Standard Model-like Higgs boson provided that the dark matter mass is about 63 GeV, 109 GeV or 126 GeV, but can be generalized to any other Higgs boson masses. Here, we point out that it may be worth looking for a 63 GeV line since it could be the signature of the decay of a Standard Model-like Higgs boson produced in space, as in the case of a di-Higgs final state if mχ≃126 GeV. We show that one can set generic constraints on the Higgs boson production rates using its decay properties. In particular, using the Fermi-LAT data from the galactic center, we find that the dark matter annihilation cross section into γ+ a Standard Model-like Higgs boson produced at rest or near rest cannot exceed 〈σv〉∼a few 10−25 cm3/s or 〈σv〉∼a few 10−27 cm3/s respectively, providing us with information on the Higgs coupling to the dark matter particle. We conclude that Higgs bosons can indeed be used as messengers to explore the dark matter mass range.

Search for standard model Higgs boson production in association with aW boson using a matrix element technique at CDF inpp¯collisions ats=1.96 TeV

This paper presents a search for standard model Higgs boson production in association with a $W$ boson using events recorded by the CDF experiment in a dataset corresponding to an integrated luminosity of 5.6 fb-1. The search is performed using a matrix element technique in which the signal and background hypotheses are used to create a powerful discriminator. The discriminant output distributions for signal and background are fit to the observed events using a binned likelihood approach to search for the Higgs boson signal. We find no evidence for a Higgs boson, and 95% confidence level (C.L.) upper limits are set on the Higgs boson production rate. The observed limits range from 3.5 to 37.6 relative to the standard model expectation for Higgs boson masses between 100 and 150 GeV. The 95% C.L. expected limit is estimated from the median of an ensemble of simulated experiments and varies between 2.9 and 32.7 relative to the production rate predicted by the standard model over the Higgs boson mass range studied.

Search for Higgs Boson Production in Dilepton and Missing Energy Final States with5.4 fb−1ofpp¯Collisions ats=1.96 TeV

A search for the standard model Higgs boson is presented using events with two charged leptons and large missing transverse energy selected from 5.4 fb-1 of integrated luminosity in p-pbar collisions at sqrt(s)=1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. No significant excess of events above background predictions is found, and observed (expected) upper limits at 95% confidence level on the rate of Higgs boson production are derived that are a factor of 1.55 (1.36) above the predicted standard model cross section at Higgs boson mass of 165 GeV.

Smoking Guns for On-Shell New Physics at the LHC

Using Tevatron bounds we derive upper limits on the LHC Higgs boson production rate assuming that no beyond the standard model (BSM) particles are being produced near their mass shell. A violation of these limits would constitute a smoking gun for light BSM particles. Furthermore, we demonstrate how R(T), the ratio of the partially integrated Higgs transverse momentum distribution to the inclusive rate, can also be used as a probe of light BSM particles. This ratio is insensitive to heavy virtual effects and is approximately model independent. The perturbative expansion for R(T) has reduced renormalization scale dependence, due to a cancellation of Wilson coefficients. A deviation from the SM value implies that light BSM particles are being produced near their mass shell. A model with colored scalars is used to investigate the model independence of R(T).

Search for a Standard Model Higgs Boson inWH→ℓvbb¯inpp¯Collisions ats=1.96 TeV

We present a search for a standard model Higgs boson produced in association with a W boson using 2.7 1/fb of integrated luminosity of pbar-p collision data taken at sqrt{s} = 1.96 TeV. Limits on the Higgs boson production rate are obtained for masses between 100 GeV and 150 GeV. Through the use of multivariate techniques, the analysis achieves an observed (expected) 95% confidence level upper limit of 5.6 (4.8) times the theoretically expected production cross section for a standard model Higgs boson with a mass of 115 GeV.

Probing theCPnature of Higgs boson throughe−e+→e−e+ϕ

We study the production of Higgs boson ($\ensuremath{\phi}$) via the ${e}^{\ensuremath{-}}{e}^{+}\ensuremath{\rightarrow}{e}^{\ensuremath{-}}{e}^{+}\ensuremath{\phi}$ process at a future International Linear Collider (ILC) with $\sqrt{S}=1\text{ }\text{ }\mathrm{TeV}$. At this energy the $ZZ$-fusion rate, as predicted by the standard model, dominates over the associated $ZH$ production rate. Here, we consider a class of theory models based on the effective $\ensuremath{\phi}VV$ (with $V=Z$, $\ensuremath{\gamma}$) couplings generated by dimension-6 operators. We also show how to use the kinematical distributions of the final state leptons to discriminate the $CP$-even and $CP$-odd Higgs bosons produced at the ILC, when the $\ensuremath{\phi}\ensuremath{\gamma}\ensuremath{\gamma}$ coupling dominates the Higgs boson production rate.

Flavor changing neutral currents, an extended scalar sector, and the Higgs production rate at the CERN Large Hadron Collider

We study extensions of the standard model with additional colored scalar fields which can couple directly to quarks. Natural suppression of flavor changing neutral currents implies minimal flavor violation, and fixes the scalars to transform as (8,2)1/2 under the SU(3)×SU(2)×U(1) gauge symmetry. We explore the phenomenology of the standard model with one additional (8,2)1/2 scalar, and discuss how this extension can modify flavor physics and the Higgs boson production rate at the LHC. Custodial SU(2) symmetry can be implemented for the octet scalars since they transform as a real color representation. Additional weak scale degrees of freedom needed for gauge unification are discussed.

Three-loop results for quark and gluon form factors

We study the photon–quark–quark and Higgs–gluon–gluon form factors for on-shell massless quarks and gluons in perturbative QCD. Previous third-order results for the quark case are extended by calculating the fermion-loop contributions up to the finite terms in dimensional regularization. For the gluon case the complete set of infrared poles at three loops is derived. Using the exponentiation of the form factor, the latter results are employed to extract a function entering the infrared factorization of general third-order amplitudes. We evaluate the infrared finite absolute ratio of the time-like and space-like gluon form factors up to the fourth order in the strong coupling constant. The result supports previous indications that the perturbative expansion of the Higgs boson production rate at the LHC is under control.