Single t-Quark Productions via Flavor-Changing Processes in Topcolor-Assisted Technicolor Model at Hadron Colliders

In the framework of topcolor-assisted technicolor （TC2） model, there exist tree-level flavor-changing （FC） couplings, which can result in the loop-level FC coupling tcg. Such tcg coupling can contribute significant clues at the forthcoming Large Hadron Collider （LHC） experiments. In this paper, based on the TC2 model, we study some single t-quark production processes involving tcg coupling at the Tevatron and LHC： pp（pp） → tq （q = u, d, s）, tg. We calculate the cross sections of these processes. The results show that the cross sections at the Tevatron are too small to observe the signal, but at the LHC it can reach a few pb. With the high luminosity, the LHC has considerable capability to find the single t-quark signal produced via some FC processes involving coupling tcg. On the other hand, these processes can also provide some valuable information of the coupling tcg with detailed study of the processes and furthermore provide the reliable evidence to test the TC2 model

Charged Top-Pion Production at Hadron Colliders

We studied the charged top-pion in the topcolor assisted technicolor model(TC2).If the charged top-pionsare heavy,m_(πt)>m_t+m_b,they will decay mainly via the channel π_t^+→tb^-.We also calculated the production of chargedtop-pion at the Tevatron and LHC.The cross section can reach to 100 fb at the Tevatron and dozens of pb at the LHCdepending on the mass of the top-pion.

Search for the singlet vector-like top quark in the T→tZ channel with Z→vv at hadron colliders

Based on a simplified model including a singlet vector-like top quark T with charge|Q|=2/3,we analyze the prospects of observing T via the single T production in the tZ channel with Z decaying to neutrinos at the hadronhadron colliders.This simplified model only includes two free parameters,the coupling constant g^(*)and the T quark mass m_(T).To investigate the observability of the single T production,we perform a detailed background analysis and detector simulation for the collision energies 14 TeV,27 TeV,and 100 TeV.We scan the g^(*)-m_(T)parameter space and show the exclusion and discovery capabilities on the T quark with the highest integrated luminosity designed at these colliders.Moreover,the limits from the narrow-width approximation and electro weak precision observables are considered.

Relativistic Heavy Ion Collider and the Large Hadron Collider for Heavy Ion Fusion

Heavy Ion Fusion makes use of the Relativistic Heavy Ion Collider at Brookhaven National Lab and the Large Hadron Collider in Geneva, Switzerland for Inertial Confinement Fusion. Two Storage Rings, which may or may not initially be needed, added to each of the Colliders increases the intensity of the Heavy Ion Beams making it comparable to the Total Energy delivered to the DT target by the National Ignition Facility at the Lawrence Livermore Lab. The basic Physics involved gives Heavy Ion Fusion an advantage over Laser Fusion because heavy ions have greater penetration power than photons. The Relativistic Heavy Ion Collider can be used as a Prototype Heavy Ion Fusion Reactor for the Large Hadron Collider.

Searching for Top Squark at Hadron Colliders

In this talk we briefly summarise our recent study(hep-ph/0007165)on searching fortop squark at hadron colliders.The light top-squark(stop)if produced in hadron colliders in theform of the (?)(?) pair and decaying through the likely decay chain (?)→(?)+b followed

Exploration of heavy Higgs bosons at a 100 TeV hadron collider within the semi-constrained next-to-minimal supersymmetric standard model

In this study,we explore the detectability of heavy Higgs bosons in the pp→bbH/A→bbtt channel at a100 TeV hadron collider within the semi-constrained next-to-minimal supersymmetric standard model.We calculate their production cross sections and decay branching ratios and compare them with simulation results from literature.We focus on the heavy doublet-dominated CP-even Higgs H and CP-odd Higgs A,with mass limits set below 10TeV to ensure detectability.At a collider with an integrated luminosity of 3 ab^(-1),the potential for detecting heavy Higgs bosons varies significantly with their mass and tanβ.Heavy Higgs bosons with masses below 2 TeV are within the testable range,while those heavier than 7 TeV are below the exclusion and discovery thresholds,rendering them undetectable.For masses between 2 and 7 TeV,heavy Higgs bosons with tanβ smaller than 20 can be detected,whereas those with tanβ larger than 20 are beyond the current discovery or exclusion capabilities.

Probing the TC2 model via Production of Top Quark Pairs at Tevatron and LHC

The topcolour-assisted technicolour （TC2） model is an interesting dynamical theory among the various new physics models. We cMculate the total tt cross section and the relative correction of the TC2 model to the cross section at Tevatron Run Ⅱ and LHC. At the Tevatron Run Ⅱ, the cross section predicted by the standard model （SM） is consistent with the experimental data, and in most parameter spaces of the TC2 model, the relative correction of the TC2 model to the cross section is too small to be detectable. We find that the tt cross section is more sensitive to the parameters of the TC2 model at the LHC and the relative correction of the TC2 model to the cross section is over 10% in general. Such a value of the relative correction should be large enough to be detectable at the LHC. Therefore, it is promising to find the clue of the TC2 model via the tt production at the LHC.

Neutral Higgs Boson Pair Production in Standard Model with the Fourth GenerationQuarks at LHC

We investigated the neutral Higgs boson pair production at the CERN Large Hadron Collider (LHC) in the SM with four families. We found that the gluon-gluon fusion mode is the most dominant one in producing neutral Higgs boson pair at the LHC, and it can be used to probe the trilinear Higgs coupling. If the heavy quarks of the fourth generation really exist within the SM, they can manifest their effect on the cross section of the Higgs pair production process at the LHC. Our numerical results show that there will be neutral Higgs boson pair production events per year if the next generation heavy quarks really exist, while there will be only events produced per year if there are only three families in the SM.

Associated ZH and WH Production in Left-Right Twin Higgs Model at LHC

At the CERN large hadron collider （LHC）, production of the Higgs boson in association with Z or W bosons provides a dramatic experimental signal for detecting the standard model （SM） Higgs boson. In this paper, we consider the contributions of the left-right twin Higgs （LRTH） model to the processes qq＇ --~ Z（W）H. Our numerical results show that, in the favorable parameter spaces, the cross sections deviate distinctly from the predictions of the SM. The possible signals of the LRTH model can be detected via these processes at the LHC experiments.

Search for production of dark fermion candidates in association with heavy neutral gauge boson decaying to dimuon in proton-proton collisions at√s=8 TeV using CMS open data

In this study,we conducted a search for dark matter using a part of the data recorded by the CMS experiment during run-I of the LHC in 2012 with a center of mass energy of 8 TeV and an integrated luminosity of 11.6 fb−1.These data were gathered from the CMS open data.Dark matter,in the framework of the simplified model(mono-Z′),can be produced from proton-proton collisions in association with a new hypothetical gauge boson,Z′.Thus,the search was conducted in the dimuon plus large missing transverse momentum channel.One benchmark scenario of mono-Z′,which is known as light vector,was used for interpreting the CMS open data.No evidence of dark matter was observed,and exclusion limits were set on the masses of dark matter and Z′at 95%confidence level.

Searches for the technicolor signatures via gg→W～(±)π_t～(■) at the Large Hadron Collider

In this paper, we calculate the production of a charged top pion in association with a W boson via gg fusion at CERN＇s Large Hadron Collider in the context of the topcolor assisted technicolor model. We find that the total cross section of pp → gg → W±＋πtT is several dozen femtobarns with reasonable values of the parameters, and the total cross section of pp→ W±＋πtT can reach a few hundred femtobarns when we consider the sum of the contributions of these two parton subprocesses, gg→ W±＋πtT and bb→W±＋πtT.

Prospects of gluino searches in multi-lepton channels in light of the ongoing LHC RUN-Ⅲ

This study investigates the prospect of discovering strongly interacting gluinos in different multi-lepton channels with lepton multiplicities greater than or equal to 2 at LHC RUN-Ⅲ,considering several pMSSM scenarios.The effectiveness of the multivariate analysis(MVA) method with the boosted decision tree(BDT) algorithm is explored to obtain a better significance for different models.Promising results are obtained for the 3-lepton channels,indicating that the use of MVA methods can improve the sensitivity of the search for gluinos at LHC RUN-Ⅲ.The study probes the multi-lepton signatures arising from gluinos via intermediate eweakinos and sleptons at an early stage of the LHC RUN-Ⅲ.The heavier eweakinos can give rise to three or four lepton signals,in which the squark hierarchy between the L and R types plays a crucial role.The study considers two sets of benchmark points that satisfy all the collider constraints obtained from the LHC RUN-Ⅱ data.Moreover,these sets of benchmark points are mostly consistent with WMAP/PLANCK data and the muon(g-2) constraint.The corresponding results from the MVA technique demonstrate that,even for an integrated luminosity of 270 fb-1,the 5 σ discovery prospect of3l+jets+ETfor Mg=1.8 TeV in the wino type model is promising.The study also presents various other models that may emerge at the early stage of LHC RUN-Ⅲ.Wino type models in the scenario where left squarks are light and right squarks are heavy exhibit the best prospect of discovering gluinos in multi-lepton channels in the LHC RUN-Ⅲ experiment.The findings of this study provide crucial insights into the potential discovery of gluinos in multi-lepton channels.

Low energy SUSY confronted with new measurements of W-boson mass and muon g-2

The new CDF II measurement of W-boson mass shows a 7σdeviation from the standard model(SM)prediction,while the recent FNAL measurement of the muon g-2 shows a 4.2σdeviation(combined with the BNL result)from the SM.Both of them strongly indicate new physics beyond the SM.In this work,we study the implication of both measurements on low energy supersymmetry.With an extensive exploration of the parameter space of the minimal supersymmetric standard model(MSSM),we find that in the parameter space allowed by current experimental constraints from colliders and dark matter detections,the MSSM can simultaneously explain both measurements on the edge of 2σlevel,taking theoretical uncertainties into consideration.The favored parameter space,characterized by a compressed spectrum between bino,wino and stau,with the stop being around 1 TeV,may be covered in the near future LHC searches.

Reduction of PDF uncertainty in the measurement of the weak mixing angle at the ATLAS experiment

We investigate the parton distribution function(PDF)uncertainty in the measurement of the effective weak mixing angle sin2θ^(l)_(eff)at the CERN Large Hadron Collider(LHC).The PDF-induced uncertainty is large in proton-proton collisions at the LHC due to the dilution effect.The measurement of the Drell-Yan forward-backward asymmetry(ApB)at the LHC can be used to reduce the PDF uncertainty in the sin2θ^(l)_(eff)measurement.However,when including the full mass range of lepton pairs in the AFB data analysis,the correlation between the PDF updating procedure and the sin2θ^(l)_(eff) extraction leads to a sizable bias in the obtained sin2θ^(l)_(eff)value.From our studies,we find that the bias can be significantly reduced by removing Drell-Yan events with invariant mass around the Z-pole region,while most of the sensitivity in reducing the PDF uncertainty remains.Furthermore,the lepton charge asymmetry in the^boson events as a function of the rapidity of the charged leptons,A±(ηl),is known to be another observable which can be used to reduce the PDF uncertainty in the sin2θ^(l)_(eff)measurement.The constraint from A±(ηl)is complementary to that from AFB,and thus no bias affects the sin2θ^(l)_(eff)extraction.The studies are performed using the error PDF Updating Method Package(ePump),which is based on Hessian updating methods.In this article,the CT14HERA2 PDF set is used as an example.

Constraints on anomalous quartic gauge couplings via Wγjj production at the LHC

Vector boson scattering at the Large Hadron Collider(LHC)is sensitive to anomalous quartic gauge couplings(aQGCs).In this study,we investigate the aQGC contribution to Wγjj production at the LHC with√s=13 TeV in the context of an effective field theory(EFT).The unitarity bound is applied as a cut on the energy scale of this production process,which is found to have significant suppressive effects on signals.To enhance the statistical significance,we analyze the kinematic and polarization features of the aQGC signals in detail.We find that the polarization effects induced by aQGCs are unique and can discriminate the signals from the SM backgrounds well.With the proposed event selection strategy,we obtain the constraints on the coefficients of dimension-8 operators with current luminosity.The results indicate that the process pp→Wγjj is powerful for searching for the OM2,3,4,5 and OT5,6,7 operators.

Search for dark matter production in association with the Z′ boson at the LHC in pp collisions at √s=8 TeV using Monte Carlo simulations

This analysis evaluates the possibility of the search for Dark Matter(DM)particles using events with a Zf heavy gauge boson and a large missing transverse momentum at the Large Hadron Collider(LHC).We consider the muonic decay of Z'.The analyzed Monte Carlo samples were the Open simulated files produced by the Compact Muon Solenoid(CMS)collaboration for proton-proton collisions,corresponding to an integrated luminosity of the LHC run-I with 19.7 fb^(-1) at √s=8 TeV.Two scenarios,namely a simplified benchmark scenario,called Dark Higgs,and the effective field theory(EFT)formalism,were used for interpretations.Limits were set on Z′,dark matter masses,and the cutoff scale of the EFT.

Discovery potential of Higgs boson pair production through 4■+■ final states at a 100 TeV collider

We explore the discovery potential of Higgs pair production at a 100 Te V collider via full leptonic mode.The same mode can be explored at the LHC when Higgs pair production is enhanced by new physics. We examine two types of fully leptonic final states and propose a partial reconstruction method, which can reconstruct some useful kinematic observables. It is found that the m T2 variable determined by this reconstruction method and the reconstructed visible Higgs mass are crucial to discriminate the signal and background events. It is also noticed that a new variable, denoted as △m, which is defined as the mass difference of two possible combinations, is very useful as a discriminant. To examine the detector effects, we consider seven detector setups for a 100 Te V collider and investigate the changes in the sensitivity, and we find that lepton isolation and the minimal lepton P t cut are crucial in order to reduce the integrated luminosity.

Searches for dark matter via charged Higgs pair production in the Inert Doublet Model at a γγ collider

The Inert Doublet Model(IDM)is one of the simplest extensions beyond the Standard Model(SM)with an extended scalar sector,which provides a scalar dark matter particle candidate.In this study,we investigated the double charged Higgs production at aγγcollider.By scanning the whole parameter space,we obtained the parameter points corresponding to the correct relic abundance of dark matter.After applying all theoretical and experimental constraints,the parameter space for the existence of dark matter was extremely restricted.We performed an analysis of the signal of H+H-production in the IDM and the SM background,with the optimized selection conditions chosen for the kinematic variables to maximize the signal significance.Comparing the signal with the background,we obtained the parameter points that may be detected in futureγγcollider experiments.

Searches for Dark Matter via Mono-W Production in Inert Doublet Model at the LHC

The Inert Doublet Model(IDM) is one of the many beyond Standard Model scenarios with an extended scalar sector, which provide a suitable dark matter particle candidate. Dark matter associated visible particle production at high energy colliders provides a unique way to determine the microscopic properties of the dark matter particle. In this paper, we investigate that the mono-W + missing transverse energy production at the Large Hadron Collider(LHC),where W boson decay to a lepton and a neutrino. We perform the analysis for the signal of mono-W production in the IDM and the Standard Model(SM) backgrounds, and the optimized criteria employing suitable cuts are chosen in kinematic variables to maximize signal significance. We also investigate the discovery potential in several benchmark scenarios at the 14 TeV LHC. When the light Z_2 odd scalar higgs of mass is about 65 GeV, charged Higgs is in the mass range from 120 GeV to 250 GeV, it provides the best possibility with a signal significance of about 3σ at an integrated luminosity of about 3000 fb^(-1).

Production and decay of the 125 GeV Higgs boson in the littlest Higgs model with T-parity

Motivated by recent search results for the standard model （SM） Higgs boson at the Large Hadron Collider （LHC）, we revisit the Higgs phenomenology in the littlest Higgs model with T-parity （LHT）. We present the signal strength modifier ix, respectively, for the main search channels qq＇→ jjh → jjγγ, qq＇→Vh →Vγγ, qq＇→Vh→ Vbb, gg→ h→ γγ, and gg→h→ VV in the LHT model. It is found that an enhancement factor of 1.09-1.56 in the qq＇→jjh→jjγγ channel can be obtained for this model in Case B with parameter f in the range 500 1000 GeV. However, the rates for bb, ττ are significantly suppressed relative to the SM predictions, which are still consistent with the current sensitivity. It is hoped that this will be further tested with larger integrated luminosity at the LHC.