Higgs Boson Detection Research Articles

Anomalous Higgs oscillations mediated by Berry curvature and quantum metric

Higgs spectroscopy, the study of Higgs bosons of a superconductor, is an emerging field in studying superconductivity. Here we show that the Berry curvature and the quantum metric of bands play a central role in the Higgs mode generation. They allow the detection of Higgs bosons even when the conventional contribution from the band curvature vanishes. Furthermore, we show that the Higgs mode can couple to the external electromagnetic field linearly when mediated by the Berry connection. As a result, we predict the existence of a second harmonic generation, in addition to the well-known third harmonic generation. We elucidate our theory further by considering a flat band superconductor realized by the Harper-Hubbard model and show that the geometric Higgs mode is lower bounded by the band Chern number. We demonstrate in twisted bilayer graphene the existence of the geometrically induced Higgs modes when superconductivity is realized in the nearly flat band at the magic angle.

A Clifford algebra approach to chiral symmetry breaking and fermion mass hierarchies

We propose a Clifford algebra approach to chiral symmetry breaking and fermion mass hierarchies in the context of composite Higgs bosons. Standard model fermions are represented by algebraic spinors of six-dimensional binary Clifford algebra, while ternary Clifford algebra-related flavor projection operators control allowable flavor-mixing interactions. There are three composite electroweak Higgs bosons resulted from top quark, tau neutrino, and tau lepton condensations. Each of the three condensations gives rise to masses of four different fermions. The fermion mass hierarchies within these three groups are determined by four-fermion condensations, which break two global chiral symmetries. The four-fermion condensations induce axion-like pseudo-Nambu–Goldstone bosons and can be dark matter candidates. In addition to the 125 GeV Higgs boson observed at the Large Hadron Collider, we anticipate detection of tau neutrino composite Higgs boson via the charm quark decay channel.

Construction of neutrino models with non-vanishing θ13 and leptogenesis

We construct the neutrino mass models with non-vanishing θ13 and estimate the baryon asymmetry of the universe and subsequently derive the constraints on the inflaton mass and the reheating temperature after inflation. The great discovery of this decade, the detection of Higgs boson of mass 126 GeV and nonzero θ13, makes leptogenesis all the more exciting. Besides, the neutrino mass model is compatible with inflaton mass 1010–1013 GeV corresponding to reheating temperature TR ∼ 105–107 GeV to overcome the gravitino constraint in supersymmetry and big bang nucleosynthesis. When Daya Bay data θ13 ≈ 9° is included in the model, τ predominates over e and μ contributions, which are indeed a good sign. It is shown that neutrino mass models for a successful leptogenesis can be accommodated for a variety of inflationary models with a rather wide ranging inflationary scale.

Detection of Charged Higgs Bosons in e+e−(γγ) → tb̄φ− Production at the ILC

In the context of the left-right twin Higgs (LRTH) model, we have studied the charged Higgs bosons production processes e+e−(γγ) → tb̄φ− at the International Linear Collider (ILC). It is found that the cross sections of these two processes could reach a few fb with reasonable parameter values. With the yearly integrated luminosity of ℒ = 500fb−1 expected at the ILC, one could collect hundreds up to thousands of charged Higgs events via these two processes. Therefore, our researches in this paper can help us search for charged Higgs bosons, and furthermore, to test the LRTH model.

Drell--Yan Processes with WINHAC

We present the Monte Carlo event generator WINHAC for Drell-Yan processes in proton-proton, proton-antiproton, proton-ion and ion-ion collisions. It features multiphoton radiation within the Yennie-Frautschi-Suura exclusive exponentiation scheme with O(alpha) electroweak corrections for the charged-current (W+/W-) processes and multiphoton radiation generated by PHOTOS for neutral-current (Z+gamma) ones. For the initial-state QCD/QED parton shower and hadronisation it is interfaced with PYTHIA. It includes several options, e.g. for the polarized W-boson production, generation of weighted/unweighted events, etc. WINHAC was cross-checked numerically at the per-mille level with independent Monte Carlo programs, such as HORACE and SANC. It has been used as a basic tool for developing and testing some new methods of precise measurements of the Standard Model parameters at the LHC, in particular the W-boson mass. Recently, it has been applied to simulations of double Drell-Yan processes resulting from double-parton scattering, in order to assess their influence on the Higgs-boson detection at the LHC in its ZZ and W+W- decay channels.

Higgs bosons at 98 and 125 GeV at LEP and the LHC

Abstract We discuss NMSSM scenarios in which the lightest Higgs boson h 1 is consistent with the small LEP excess at ~ 98 GeV in e + e − → Zh with $ h\to b\overline{b} $ and the heavier Higgs boson h 2 has the primary features of the LHC Higgs-like signals at 125 GeV, including an enhanced γγ rate. Verification or falsification of the 98 GeV h 1 may be possible at the LHC during the 14 TeV run. The detection of the other NMSSM Higgs bosons at the LHC and future colliders is also discussed, as well as dark matter properties of the scenario under consideration.

Probing 3-3-1 models in diphoton Higgs boson decay

We investigate the Higgs boson production through gluon fusion and its decay into two photons at the LHC in the context of the minimal 3-3-1 model and its alternative version with exotic leptons. The diphoton Higgs decay channel presents an enhanced signal in this model compared to the Standard Model due to the presence of an extra singly charged vector boson and a doubly charged one. Prospects for the Higgs boson detection at 7 TeV center-of-mass energy with up to 10 fb$^{-1}$ are presented. Our results suggest that a Higgs boson from these 3-3-1 models can potentially explain the small excess for $m_H\leq 145$ GeV observed at the LHC. Otherwise, if this excess reveals to be only a statistical fluctuation of the Standard Model backgrounds severe constraints can be put on these models.

Estimations for the Higgs boson production with QCD and EW corrections in exclusive events at the LHC

The Higgs boson production is investigated in proton-proton collisions at next-to-leading-order accuracy in central exclusive diffractive processes at the LHC. The production process by the double Pomeron exchange is analyzed in the diffractive factorization through the Ingelman-Schlein approach, taking into account the parton content of the Pomeron by the diffractive partonic distribution function provided by the H1 Collaboration. Hence, we estimate the production cross section of the Higgs boson as well as its rapidity distribution for distinct energies of the LHC. Also, we include the gap survival probability in our calculation, which is studied in recent works and expected to lie in the range between 1% and 5% for the energy regime of 14 TeV. As a result, we found a production cross section of about 0.3--0.8 (1.2--3.7) fb at 7 (14) TeV, being of the same order as predicted by the two-photon and the Balitsky-Fadin-Kuraev-Lipatov Pomeron mechanisms. Therefore, assuming the selection rules of spin-parity properties, the exclusive production is a promising channel for the Higgs boson detection in the LHC.

Challenges for MSSM Higgs boson searches at hadron colliders

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 themore » B-physics allowed regions for small or moderate values of the stop mixing parameter.« less

Tagging b jets associated with heavy neutral MSSM Higgs bosons

Since a neural network (NN) approach has been shown to be applicable to the problem of Higgs boson detection at LHC [I. Iashvili, A. Kharchilava, CMS TN-1996/100; M. Mjahed, Nucl. Phys. B 140 (2005) 799], we study the use of NNs in the problem of tagging b jets in pp → b b ¯ H SUSY , H SUSY → τ τ in the Compact Muons Solenoid experiment [F. Hakl, et al., Nucl. Instr. and Meth. A 502 (2003) 489; S. Lehti, CMS NOTE-2001/019; G. Segneri, F. Palla, CMS NOTE-2002/046]. B tagging is an important tool for separating the Higgs events with associated b jets from the Drell–Yan background Z , γ * → τ τ , for which the associated jets are mostly light quark and gluon jets. We teach multi-layer perceptrons (MLPs) available in the object oriented implementation of data analysis framework ROOT [ROOT—An Object Oriented Data Analysis Framework, in: Proceedings of the AIHENP’96 Workshop, Lausanne, September 1996, Nucl. Instr. and Meth. A 389 (1997) 81]. The following learning methods are evaluated: steepest descent algorithm, (BFGS) Broyden–Fletcher–Goldfarb–Shanno algorithm, and variants of conjugate gradients. The ROOT code generation feature of standalone C++ classifiers is utilized. We compare the b tagging performance of MLPs with another ROOT based feed forward NN tool NeuNet [J.P. Ernenwein, NeuNet software for ROOT], which uses a common back-propagation learning method. In addition, we demonstrate the use of the self-organizing map program package (SOM_PAK) and the learning vector quantization program package (LVQ_PAK) [T. Kohonen, et al., SOM_PAK: the self-organizing map program package, Technical Report A31; T. Kohonen, et al., LVQ_PAK: the learning vector quantization program package, Technical Report A30, Laboratory of Computer and Information Science, Helsinki University of Technology, FIN-02150 Espoo, Finland, 1996] in the b tagging problem.

Status of the CMS PbWO 4 Electromagnetic Calorimeter

In the mass range of 110-150 GeV the favored process for Higgs boson detection via p-p collisions is via its decay into two photons, which demands a very high-resolution electromagnetic calorimeter. This physics goal plus the Large Hadron Calorimeter (LHC)-imposed design constraints of 25ns bunch spacing and a hostile radiation environment have led the Compact Muon Solenoid (CMS) collaboration to the choice of lead tungstate (PbWO4) crystals. Their relatively low room-temperature scintillation photon yield plus the presence of a 4T magnetic field have motivated the choice of photodetection devices providing gain amplification: Avalanche photodiodes (APD) in the central barrel region and vacuum phototriodes (VPT) in the forward endcap regions. In 2002 and 2003 significant changes were undertaken to the radiation-hard ∼95dB-dynamic-range readout electronics system, which now features 0.25μm CMOS ASICs, and which has been tested for the first time in particle beams. The CMS electromagnetic calorimeter is now in the construction phase. We review progress in the areas of crystals, barrel and endcap photodetection devices, the implementation of the readout electronics system redesign and the scintillation light loss monitoring system, as well as the status of assembly and quality control. We also present selected results from the autumn 2003 test beam program including noise performance obtained with the redesigned readout electronics, and irradiation studies demonstrating the performance of the laser monitoring system.

Phenomenology of nonuniversal gaugino masses in supersymmetric grand unified theories

Grand unified theories can lead to non-universal boundary conditions for the gaugino masses at the unification scale. We consider the implications of such non-universal boundary conditions for the composition of the lightest neutralino as well as for the upper bound on its mass in the simplest supersymmetric grand unified theory based on the SU(5) gauge group. We derive sum rules for neutralino and chargino masses in different representations of SU(5) which lead to different non-universal boundary conditions for the gaugino masses at the unification scale. We also consider the phenomenological implications of the non-universal gaugino masses arising from a grand unified theory in the context of Large Hadron Collider. In particular we investigate the detection of heavy neutral Higgs bosons $H^0, A^0$ from $H^0, A^0 \to \tilde{\chi}_2^0 \tilde{\chi}_2^0 \to 4l $, and study the possibilities of detecting the neutral Higgs bosons in cascade decays, including the decays $\tilde{\chi}_i^0 \to h^0 (H^0, A^0) \tilde{\chi}_1^0 \to b\bar{b} \tilde{\chi}_1^0$.

Measuring the fermionic couplings of the Higgs boson at future colliders as a probe of a nonminimal flavor structure

We study the fermionic couplings of the neutral Higgs bosons in the THDM, assuming a four-texture structure for the Yukawa matrices. We then derive the low-energy constraints on the model, focusing in b-quark and lepton physics, and apply them to study Higgs boson detection at future colliders.

Detection of MSSM Higgs bosons from supersymmetric particle cascade decays at the LHC

In the context of the minimal supersymmetric extension of the Standard Model, we study the production of Higgs bosons at the large hadron collider via cascade decays of scalar quarks and gluinos. We focus on the cascades involving heavier charginos and neutralinos, which decay into the neutral h, A, H and charged H ± bosons and lighter charginos and neutralinos, but we will also discuss direct decays of third-generation squarks into their lighter partners and Higgs bosons as well as top quark decays into H ± bosons. We show that the production rates of relatively light Higgs bosons, M Φ ≲250 GeV, via these mechanisms can be rather large in some areas of the parameter space. Performing a fast detector simulation analysis that takes into account the signals and the various backgrounds, we show that the detection of the neutral Higgs bosons through their decays into b b ̄ pairs, and of the charged Higgs particles through the τ ± ν signature, is possible at the LHC.

Recent developments in crystal calorimeters (featuring the CMS PbWO 4 electromagnetic calorimeter)

In the mass range of 110–150 GeV the favored process for Higgs boson detection via p-p collisions is via its decay into two photons, which demands a very high-resolution electromagnetic calorimeter. This physics goal plus the Large Hadron Calorimeter (LHC)-imposed design constraints of 25ns bunch spacing and a hostile radiation environment have led the Compact Muon Solenoid (CMS) collaboration to the choice of lead tungstate (PbWO 4) crystals. These factors plus the presence of a 4T magnetic field and the relatively low room-temperature scintillation photon yield of PbWO 4 make photodetection a real challenge, which CMS has met via the choice of devices providing gain amplification: Avalanche photodiodes (APD) in the central barrel region and vacuum phototriodes (VPT) in the forward and backward endcap regions. In the past year the CMS electromagnetic calorimeter has entered the construction phase. We review progress in the areas of crystals, barrel and endcap photodetection devices, plans for detector calibration as well as the status of assembly and quality control. We also invoke relevant developments in other crystal calorimeters currently in operation or under development. Crystal calorimeters remain the medium of choice for precision energy and position measurements in high energy physics.

Application of neural networks to Higgs boson search

Abstract This paper describes an application of a neural network (NN) approach to standard model and minimal supersymmetry standard model Higgs search in the associated production t t H with H → b b . This decay channel is considered as a discovery channel for Higgs scenarios for Higgs boson masses in the range 80– 130 GeV . An NN model with a special type of data flow is used to separate t t jj background from H → b b events. This NN combines a classical NN and linear decision tree. Parameters of these NNs are randomly generated and a population of predefined size of those networks is trained as an initial generation for a subsequent genetic algorithm optimization. A genetic algorithm tunes parameters of further NN individuals derived from the previous NNs by GA operations of crossover and mutation. The goal of this GA process is optimization of the final NN performance. Our results show that NN approach is applicable to the problem of Higgs boson detection. NN filters can be used to emphasize the difference of the Mbb distribution for events accepted by filter (with better signal/background rate) and the Mbb distribution for original events (with original signal/background rate) with no loss of significance. This improvement of the shape of the Mbb distribution can be used as a criterion for existence of Higgs boson decay in considered discovery channel.

Detection of heavy charged Higgs bosons at future Linear Colliders

We show how a statistically significant signal of heavy charged Higgs bosons of a general Two-Higgs Doublet Model produced in association with tau-neutrino pairs can be established at future Linear Colliders in the \(H^+ \rightarrow t{\bar b} \rightarrow 4\) jet decay channel. This signature is particularly relevant in the kinematic configuration \({\sqrt{s}}\lesssim 2M_{H\pm}\), when the pair production channel \(e^+ e^- \rightarrow H^+ H^-\) is no longer available. Here, the initially overwhelming background, constituted by top quark pair production and decay, can vigorously be reduced thanks to a dedicated selection procedure that allows one to extract a signal in a region of several tens of GeV around \(M_{H\pm} \approx {\sqrt{s}}/2\), for tan \(\beta \gtrsim 40\).

Inclusive Higgs Boson and Dijet Production via Double Pomeron Exchange

We evaluate inclusive Higgs boson and dijet cross sections at the Fermilab Tevatron collider via double Pomeron exchange. Such inclusive processes, normalized to the observed dijet rate observed at Run I, noticeably increase the predictions for tagged (anti)protons in Run II with respect to exclusive production, with the potentiality of Higgs boson detection.

High $p_T$ Higgs signal for the LHC

We show that the broad transverse momentum distribution of the Higgs boson produced by WW fusion can provide a viable way to identify H --> b anti-b decays at the LHC, if particular kinematical configurations with large rapidity gaps are selected. We estimate the event rate of the signal and of the QCD b anti-b background. We also discuss Higgs boson detection via the H --> tau tau and H --> WW* decay modes.

The Compact Muon Solenoid (CMS) electromagnetic calorimeter

The Electromagnetic Calorimeter of the CMS detector for the CERN Large Hadron Collider (LHC) is designed to allow the detection of a standard model Higgs boson of mass below 150 GeV. An overview is given of this homogeneous calorimeter made of almost 80 000 lead tungstate (PbWO 4) 26 X 0 long crystals. This includes a description of the engineering design and a review of the different components of the calorimeter. The most recent results obtained in particle beams with realistic crystal prototypes are also presented.