Gunnar Klamke, Dieter Zeppenfeld
Higgs boson production in association with two tagging jets will be mediated by electroweak vector boson fusion and by gluon fusion. For the gluon fusion process, analysis of the azimuthal angle correlations of the two jets provides for a direct measurement of the CP-nature of the $Htt$ Yukawa coupling which is responsible for the effective $Hgg$ vertex.
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Studying the VBF Hjj and Hjjj Higgs Boson Production in QCD and EFT Theory
本研究在QCD和EFT理论框架下，探讨了VBF机制中Hjj和Hjjj喷注的希格斯玻色子产生过程，计算了其截面并应用于标准模型及扩展模型。
At lowest order in perturbation theory, the scattering matrix element for Higgs boson production in association with dijets displays a strong correlation in the azimuthal angle between the dijets, induced by the CP-properties of the Higgs Boson coupling. However, the phase space cuts necessary for a clean extraction of the CP-properties simultaneously induce large corrections from emissions of hard radiation and thus formation of extra jets. The current study concerns the generalization of CP-studies using the azimuthal angle between dijets beyond tree-level and to events with more than just t…
We present a calculation of interference effects in Hjj production via gluon fusion and via vector boson fusion, respectively, beyond tree level. We reproduce results recently discussed in the literature, but go beyond this calculation by including a class of diagrams not considered previously. Special care is taken in developing a numerically stable and flexible parton level Monte-Carlo program which allows us to study cross sections and kinematic distributions within experimentally relevant selection cuts. Loop-induced interference contributions are found to exhibit kinematical distributions…
Constraining Lepton Flavor Violating Higgs Couplings at the HL-LHC in the Vector Boson Fusion Channel
本研究在HL-LHC上通过VBF道探测μ-τ轻子味破缺希格斯耦合，对比低能约束给出标准模型希格斯的灵敏度，还给出了通用新中性希格斯的模型无关上限并以双希格斯二重态模型解读。
Experimental falsification or validation of the Standard Model of Particle Physics involves the measurement of the CP quantum number and couplings of the Higgs boson. Both ATLAS and CMS have reported an SM Higgs-like excess around m_H=125 GeV. In this mass range the properties of the Higgs boson can be extracted from an analysis of the azimuthal angle distribution of the two jets in pp->Hjj events. This channel is also important to measure the couplings of the Higgs boson to electroweak gauge bosons and fermions, hereby establishing the exceptional role of the Higgs boson in the Standard Model…
We review the theoretical status of signal and background calculations for Higgs boson production at hadron colliders. Particular emphasis is given to missing NLO results, which will play a crucial role for the Tevatron and the LHC.
We examine the structure of the underlying event in neutral Higgs production at the Superconducting-Supercollider (SSC). Gaps, regions of rapidity containing no soft particle production, can provide a clean signature for $W$ boson fusion to the heavy Higgs. We first examine the physical basis of gap production and estimate the survival probability of gaps in the minijet model. Then, using PYTHIA, and HERWIG we compare gap events to $W$ pair production from top decay and $q\bar{q}$ fusion. We find that, if experimental problems can be overcome, gaps should provide a small, but clean, signal for…
We discuss the production of W bosons in association with three jets at the LHC. We investigate how next-to-leading order QCD corrections modify basic kinematic distributions of jets and leptons. We also address the magnitude of NLO QCD effects in W+3 jet observables, relevant for SUSY searches at the LHC.
In this paper, the t-channel charged Higgs production at LHC is studied. Production process is a t-channel single top event with charged Higgs exchange. Therefore the signal is similar with Standard Model single top production in terms of the final state. In the first step, the signal cross section is calculated and compared to the other main production processes which are used for a heavy charged Higgs search at LHC, i.e., pp -> tbH- and pp -> H+ -> tb. In the next step, an event generation and analysis is applied on signal and background events, in order to estimate the signal significance. …
Higgs boson production in association with two tagging jets will be mediated by electroweak vector boson fusion and by gluon fusion processes at the CERN LHC. The characteristic distributions for the gluon fusion process are analyzed for the $H\to W^+W^-$ signal at $m_H=160$ GeV, with subsequent leptonic decay of the $W$-pair. The dominant backgrounds from top-quark pair production, $WWjj$ production and vector boson fusion processes can be suppressed to a level of $S/B\approx 1/4$, yielding a highly significant gluon fusion signal with 30 fb$^{-1}$. Analysis of the azimuthal angle correlation…
Standard Model predictions for the reactions with six fermions in the final state relevant for top quark pair production and decay at linear colliders are discussed. An issue of the double resonance signal versus non doubly resonant background is addresed. Effects related to the off-mass-shell production of the t\bar{t}-pair are discussed.
In this paper, we study central production, in the inclusive case, to look for graviton signals in large extra dimensional model using dilepton and diphoton channels. We carefully analyze signal and possible Standard Model background processes and study the feasibility of such new physics searches in a relatively clean environment as in central production where the proton fragments are mostly emitted in the forward direction, and there is a clear rapidity gap between them and the centrally produced system. Our analysis shows that the LHC with 14 TeV center of mass energy and 100 fb$^{-1}$ (300…
In this paper, the b quark pair production events are analyzed as a source of neutral Higgs bosons of the two Higgs doublet model type I at linear colliders. The production mechanism is e+e- -> Z/gamma -> HA -> bbbb assuming a fully hadronic final state. The analysis aim is to identify both scalar and pseudo-scalar Higgs bosons in different benchmark points accommodating moderate boson masses. Due to pair production of Higgs bosons, the analysis is most suitable for a linear collider operating at sqrt(s) = 1 TeV. Results show that in selected benchmark points, signal peaks are observable in th…
We revisit the monophoton plus missing energy signature at $e^+e^-$ colliders in supersymmetric (SUSY) models where the gravitino is very light. There are two possible processes which provide the signal: gravitino pair production and associated gravitino production with a neutralino, leading the monophoton final state via an additional photon radiation and via the neutralino decay, respectively. By using the superspace formalism, we construct a model that allows us to study the parameter space for the both processes. We show that the signal cross section and the photon spectra provide informat…
We perform a Monte-Carlo simulation of scalar leptoquark pair production at the Tevatron (energy =1.8 TeV and luminosity =100 pb^{-1}) with ISAJET. We also investigate the dominant sources of Standard Model background: Z*jj, ZZ production and heavy quark top-antitop. We find that the top-antitop background is the most important except near the Z pole where the Z*jj background is peaked. We also evaluate the signal-to-background ratio and find a discovery reach of 130 GeV (170 GeV) for a branching ratio of B(LQ-> eq)=0.5 (B=1).
We compute complete tree level matrix elements for $gg , q \bar q \rightarrow b \bar b W^+W^-$. We analyze the irreducible backgrounds to top signal at the Tevatron and at the LHC. Their contribution to the total cross section is about $5 \%$ at the LHC, due to single resonant channels. Several distributions with contributions from signal and backgrounds are presented.
We study the production and decay of a scalar \stst\ bound state \sigst\ at hadron supercolliders, where \st\ is the lighter stop eigenstate. If \st\ has no tree--level 2--body decays, the dominant decay modes of \sigst\ are $gg$ or, if $m_h < \mst \ll \mstt$, a pair of light scalar Higgs bosons $h$. Nevertheless the branching ratio into two photons is often large enough to yield a detectable signal.
We present production rates of the two- and three-jet final states for the processes of massive $c\bar c/b\bar b$ quark production in circularly polarized photon-photon collisions, including QCD radiative corrections. Lowest order cross section, one-loop virtual correction and gluon emission correction are shown to be of the same order of magnitude for $b\bar b$ quark production at $\sqrt{s_{γγ}}\sim 100$~GeV. It is shown that the signal from intermediate mass Higgs boson is observable at photon-photon collider, although the statistical significance is substantially reduced with respect to the…
In this work pair productions of charged and doubly charged scalars in the framework of littlest Higgs model at $e^+e^-$ colliders are studied. In the allowed parameter space of the littlest Higgs model, the production rates of the scalar pairs are calculated. It is obtained that pair productions of charged and doubly charged scalars are reachable at $e^+ e^-$ colliders with energy $\sqrt{S}\geq 1.7TeV$. Using the lepton flavor violating decays of charged scalars calculated in literature, final state analysis is done for pair production processes. This analysis show that depending on the model…
We study the signals for a heavy Higgs boson in the processes $γγ\to WWWW$, $γγ\to WWZZ$ at the photon linear collider. The results are based on the first complete tree level calculation for these reactions. Using a forward ``spectator" $W$ tag, central ``spectator" $W$ veto to suppress backgrounds from transverse $W$, $Z$ production we show that the invariant mass spectrum of central $WW$, $ZZ$ pairs is sensitive to Higgs boson with a mass up to 1~TeV at a 2~TeV linear collider.
We study pair production of leptoquarks in e+e- annihilation at linear colliders. A detailed simulation including beamstrahlung and initial state radiation, leptoquark decay and hadronization, as well as detector smearing, is performed. Discovery limits are estimated for center-of-mass energies of 500 and 800 GeV. The prospects for determining masses and couplings of leptoquarks are also investigated.
In this paper, the top quark pair production events are analyzed as a source of neutral Higgs bosons of two Higgs doublet model type I at LHC. The production mechanism is $pp \to H/A \to t\bar{t}$ assuming a fully hadronic final state through $t \to Wb \to jjb$. In order to distinguish the signal from the main background which is the standard model $t\bar{t}$, we benefit from the fact that the top quarks in signal events acquire a large Lorentz boost due to the heavy neutral Higgs boson. This feature leads to three collinear jets (a fat jet) which is a discriminating tool for identification of…
We discuss signals for CP-violation in $μ^+ μ^- \to \tilde τ_i^- \tilde τ_j^+$, where $i,j = 1,2$ label the two scalar $τ$ mass eigenstates. We assume that these reactions can proceed through the production and decay of the heavy neutral Higgs bosons present in supersymmetric models. CP-violation in the Higgs sector can be probed through a rate asymmetry even with unpolarized beams, while the CP-odd phase associated with the $\tilde τ$ mass matrix can be probed only if the polarization of at least one beam can be varied. These asymmetries might be ${\cal O}(1)$.
I briefly review the construction of the effective field theory of a nonlinearly realized electroweak symmetry breaking and apply it to the study of gauge boson pair production. I will consider WW, ZZ and γZ production at linear colliders as reference illustrative examples. I will show that in all cases a consistent effective field theory treatment allows to encode the dominant new physics effects entirely as gauge-fermion vertex corrections. From naive dimensional analysis one expects these corrections to be at the per mille level. However, they grow with energy, such that at TeV colliders (L…
We discuss single top quark production via u^i+\bar d^j \to t+\bar b at the Fermilab Tevatron in the minimal supersymmetric model with R-parity violation. We find that within the allowed range of coupling constants, the lepton-number violating couplings can give rise to observable effects when the slepton mass lies in a specific narrow range. For the baryon-number violating couplings, the contribution to the production rate can be quite large in the presently allowed range of the coupling constants. We show that the measurement of single top production at the upgraded Tevatron can be used to c…
We compute the total cross section and the transverse momentum distribution for single charged slepton and sneutrino production at hadronic colliders including NLO supersymmetric and non-supersymmetric QCD corrections. The supersymmetric QCD corrections can be substantial. We also resum the gluon transverse momentum distribution and compare our results with two Monte Carlo generators. We compute branching ratios of the supersymmetric decays of the slepton and determine event rates for the like-sign dimuon final state at the Tevatron and at the LHC.
Single sparticle creation in high energy collisions as a consequence explicit $R$-parity breaking, could be a rich source of highly spectacular signals at future colliders. One particular process, which could lead to a highly exotic leptonic signal at the LHC, is monoslepton production. In this paper we qualitatively discuss the constraints on the signal for this process and calculate the hadronic monoslepton production cross section, taking into account leading QCD corrections. Our results show the leading corrections could be quite significant at the proposed LHC operating energy.
New dark matter production mechanism and the gravitational wave signals
本研究提出新的暗物质产生机制，通过引力波信号探测暗物质的起源和性质，拓展了传统宇宙学模型。
We present the results of an analysis for the pair production of scalar leptoquarks at the CERN Large Hadron Collider (LHC) with energy=14 TeV and luminosity=10 fb^{-1} which includes the dominant sources of Standard Model background associated to this process: top-antitop, ZZ, WZ and Z*jj production. The top-antitop process provides the main source of background. We consider leptoquarks introduced in the framework of a superstring-inspired E_6 model. The leptoquark production is found to be dominant in all regions of parameter space for leptoquark masses below 750 GeV. We establish the discov…
We study the potential of hadron colliders in the search for the pair production of neutral Higgs bosons in the framework of the Minimal Supersymmetric Standard Model. We perform a detailed signal and background analysis, working out efficient kinematical cuts for the extraction of the signal. The important role of squark loop contributions to the signal is re--emphasized. If the signal is sufficiently enhanced by these contributions, it could even be observable at the next run of the upgraded Tevatron collider in the near future. At the LHC the pair production of light and heavy Higgs bosons …
We present an analysis of the ψψproduction from double parton (DP) sacttering and single parton (SP) scattering in the large p_T region via color-octet gluon fragmentation. We find that at the Tevatron the DP ψψproduction is at the edge of the detectability at present, and at the LHC the DP cross section will dominate over the SP cross section in the lower p_T(min) region (i.e., p_T(min)<7GeV). We also conclude that the color-octet mechanism is of crucial importance to the double j/psi production at high energy hadron colliders.
We give evidence that the production of DCC's during a non-equilibrium phase transition can lead to an anomalous transverse distribution of secondary pions when compared to a more conventional boost invariant hydrodynamic flow in local thermal equilibrium. Our results pertain to the linear $σ$ model,treated in leading order in large-$N$, in a boost invariant approximation. We also show that the interpolating number density of the field theory calculation plays the role of a classical relativistic phase space number distribution in determining the momentum distribution of pions in the center of…
The heavy charged gauge bosons were proposed in the theories beyond standard model. We explore the discovery potential for $W'\to t\bar{b}$ with top quark semi-leptonic decay at the LHC. We concentrate on the new physics signal search with the deviation from the standard model prediction if the resonance peak of $W'$ can not be observed directly. The events of signal with two jets plus one charged lepton and missing energy are simulated together with the dominant standard model backgrounds. In this paper, it is found that suitable cuts on the kinematic observables can effectively suppress the …
We present a non-trivial correlation between the enhancement of the Higgs-fermion couplings and the Higgs pair production cross section in two Higgs doublet models with a flavour symmetry. This symmetry suppresses flavour-changing neutral couplings of the Higgs boson and allows for a partial explanation of the hierarchy in the Yukawa sector. After taking into account the constraints from electroweak precision measurements, Higgs coupling strength measurements, and unitarity and perturbativity bounds, we identify an interesting region of parameter space leading to enhanced Yukawa couplings as w…
We study a generic Higgs boson and a top quark associated production via model-independent flavor-changing neutral-current couplings at the LHC, including complete QCD next-to-leading order (NLO) corrections to the production and decay of the top quark and the Higgs boson. We find that QCD NLO corrections can increase the total production cross sections by about 48.9% and 57.9% for the $Htu$ and $Htc$ coupling induced processes at the LHC, respectively. After kinematic cuts are imposed on the decay products of the top quark and the Higgs boson, the QCD NLO corrections are reduced to 11% for th…
Strangeness enhancement is discussed as a feature specific to relativistic nuclear collisions which create a fireball of strongly interacting matter at high energy density. At very high energy this is suggested to be partonic matter, but at lower energy it should consist of yet unknown hadronic degrees of freedom. The freeze-out of this high density state to a hadron gas can tell us about properties of fireball matter. The hadron gas at the instant of its formation captures conditions directly at the QCD phase boundary at top SPS and RHIC energy, chiefly the critical temperature and energy den…
Dark matter production accompanied by gravitational wave signals during cosmological phase transitions
本研究在含两个Z₂奇标量场的Z₂模型中探究弱相互作用大质量暗物质粒子的温度依赖产生，明确三种主导产生机制，发现考虑热历史下的相变会带来独特演化轨迹，且伴随可被未来干涉仪探测的引力波信号。
In this paper, we study the observability of the top-Higgs flavor changing neutral current (FCNC) $tqh$ coupling through the process $pp\to qg\to t(\to \ell^{+}bν)h(\to γγ)$ at the Large Hadron Collider~(LHC), where $\ell=e, μ$. Our numerical results show that, in some parameter regions, the LHC may observe the above signals at the $5σ$ level. Otherwise, the branching ratios $Br(t\to uh)$ and $Br(t\to ch)$ can be respectively probed to $0.036\%$ and $0.13\%$ at $3σ$ level at 14 TeV LHC with the high integrated luminosity of 3000 fb$^{-1}$. On the other hand, studying the charge ratio for the l…
We study the single production of top quarks in $e^+e^-, ep$ and $pp$ collisions in the context of unparticle physics through the Flavor Violating (FV) unparticle vertices and compute the total cross sections for single top production as functions of scale dimension $d_{\U}$. We find that among all, LHC is the most promising facility to probe the unparticle physics via single top quark production processes.
We study the production of the Higgs boson in association with a single top quark at hadron colliders. The cross sections for the three production processes (t-channel, s-channel, and W-associated) at both the Tevatron and the LHC are presented. We investigate the possibility of detecting a signal for the largest of these processes, the t-channel process at the LHC, via the Higgs decay into b b-bar. The QCD backgrounds are large and difficult to curb, hindering the extraction of the signal. Extensions of our analysis to the production of supersymmetric Higgs bosons are also addressed. The cros…
We offer the parameter, interpreted as the "chemical potential", which is sensitive to the first order phase transition: it must decrease with number of evaporating (produced) particles (hadrons) if the (interacting hadron or/and QCD plasma) medium is boiling and it increase if no phase transition occur. The main part of the paper is devoted to the question: how one can measure the "chemical potential" in the hadron inelastic processes. Our definition of this parameter is quite general but assumes that the hadron multiplicity is sufficiently large. The simple transparent phenomenological latti…
We study the signals and backgrounds for a heavy Higgs boson in the processes $γγ\to WWWW$, $γγ\to WWZZ$ at the photon linear collider. The results are based on the complete tree level SM calculation for these reactions. We show that the invariant mass spectrum of central $WW$, $ZZ$ pairs is sensitive to the signal from Higgs boson with a mass up to 1~TeV at a 2~TeV linear collider for integrated luminosity of 300~fb$^{-1}$. At 1.5~TeV PLC Higgs boson with a mass up to 700~GeV can be studied. The nonresonant longitudinal gauge boson scattering ($m_H=\infty$) can be detected in photon-photon co…
We analyze the impact of electron and positron beam polarization on radiative neutralino production at the International Linear Collider (ILC). We focus on three different mSUGRA scenarios in turn at the Higgs strahlung threshold, the top pair production threshold, and at $\sqrt{s} =500\GeV$. In these scenarios at the corresponding $\sqrt{s}$, radiative neutralino production is the only supersymmetric production mechanism which is kinematically allowed. The heavier neutralinos, and charginos as well as the sleptons, squarks and gluinos are too heavy to be pair produced. We calculate the signal…
We study the pair production of doubly charged Higgs bosons at the Large Hadron Collider (LHC), assuming the doubly charged Higgs to be part of an SU(2)_L triplet which generates Majorana masses for left-handed neutrinos. Such pair-production has the advantage that it is not constrained by the triplet vacuum expectation value, which tends to make the single production rate rather small. We point out that, in addition to the Drell-Yan (DY) production mechanism, two-photon processes also contribute to H++H++ production at a level comparable to the QCD corrections to the DY channel. Decays of the…
The signature at the LHC of many Beyond the Standard Model (BSM) scenarios is events with large missing energy. If the forward outgoing protons are measured, we show that the production and decay of BSM particles in the central rapidity interval, with gaps in rapidity either side, offers certain advantages over inclusive production, to search for signals (a) with missing longitudinal 4-momentum (typical of invisible Higgs production), and (b) for new light pseudoscalar bosons.
A light Higgs boson with substantial branching ratio into invisible channels can occur in a variety of models with: light neutralinos, spontaneously broken lepton number, radiatively generated neutrino masses, additional singlet scalar(s) and/or right handed neutrinos in the extra dimensions of TeV scale gravity. We study the observability of the WH and ZH modes at LHC with H decaying invisibly, by carrying out a detailed simulation with two event generators HERWIG and PYTHIA and realistic detector simulations (GETJET and CMSJET). We find that the signal with `single lepton plus missing $E_T$'…
We consider a hard jet production tagged by a muon pair in ultrarelativistic heavy ion collisions. The process cross section is calculated by the CompHEP Monte-Carlo generator taking into account full gamma*/Z interference pattern at LHC energies. We have found that reasonable statistics, ~1000 events per 1 month of LHC run with lead beams, can be expected for realistic geometrical acceptance and kinematic cuts. The transverse momentum imbalance due to interactions of jet partons in the medium is evaluated for mu+mu-pair+jet correlation, as well as for the correlation between mu+mu- pair and a…
We investigate the observability of the top anomalous $tqZ$ couplings via the trilepton signatures at the Large Hadron Collider~(LHC) with the center-of-mass energy of 14 TeV. We focus on signals of the $tZ$ associated production with the decay mode $t\to W^{+}b\to b\ell^{+}ν_{\ell}$, $Z\to \ell^{+}\ell^{-}$, and $t\bar{t}$ production with the decay mode $\bar{t}\to Z(\to \ell^{+}\ell^{-})\bar{q}$ and $t\to b\ell^{+}ν_{\ell}$, where $\ell=e, μ$ and $q$ reflects up and charm quarks. It is shown that at $3σ$ level, the FCNC top quark decay branching ratios can be probed at, respectively, about $…
We discuss the production, at high--energy e$^+$e$^-$ linear colliders, of new heavy fermions predicted by extensions of the Standard Model. We analyze in great details the various signals and the corresponding backgrounds for both pair production and single production in association with ordinary fermions. Concentrating on new leptons, we use a model detector for e$^+$e$^-$ collisions at a center of mass energy of 500 GeV, to illustrate the discovery potential of the Next Linear Colliders.
We perform a detailed analysis of the potentiality of the CERN Large Hadron Collider to study the single production of leptoquarks via $pp \to e^\pm q\to$ leptoquark $\to e^\pm q$, with $e^\pm$ generated by the splitting of photons radiated by the protons. Working with the most general $SU(2)_L \otimes U(1)_Y$ invariant effective lagrangian for scalar and vector leptoquarks, we analyze in detail the leptoquark signals and backgrounds that lead to a final state containing an $e^\pm$ and a hard jet with approximately balanced transverse momenta. Our results indicate that the LHC will be able to …
Vector-like quarks (VLQs) are predicted in many new physics scenarios beyond the standard model (SM). We consider a search strategy for vector-like bottom quark (VLQ-$B$) at the LHC in a model independent fashion. Our analysis is based on single production of VLQ-$B$ with decaying to the $ Zb$ mode. The production cross sections and the signal significance $SS$ are calculated, and the observability of the VLQ-$B$ signal is investigated. Our numerical results show that the possible signals of the VLQ-$B$ with electric charge of $Q_B= -1/3$, which is the $SU(2)$ singlet, might be detected via th…
A gamma line signal in cosmic-ray observation would be found when Higgs is produced at rest or almost rest by DM annihilation because of decay of 126 GeV Higgs into two gamma. This line signal gives a constraint on Higgs production cross section by DM. We examine this point with simple analysis in this work.
In supersymmetric theories with R-parity breaking, sleptons can be produced in quark-antiquark annihilation at the Tevatron through interactions in which two quark fields are coupled to a slepton field. If at the same time trilinear slepton-lepton-lepton couplings are present, the sleptons can be searched for as resonances in $p\bar{p}\to \tildeν \to l^+l^-$ and $\tildeτ\to lν$ final states. Existing Tevatron data can be exploited to derive bounds on the Yukawa couplings of sleptons to quark and lepton pairs. Similar bounds can also be obtained from $e^+e^-$ annihilation to hadrons at LEP2.
Naturalness arguments imply the existence of higgsinos lighter than 200-300 GeV. However, because these higgsinos are nearly mass degenerate, they release very little visible energy in their decays, and signals from electroweak higgsino pair production typically remain buried under Standard Model backgrounds. Moreover, gluinos, squarks and winos may plausibly lie beyond the reach of the LHC14, so that signals from naturalness-inspired supersymmetric models may well remain hidden via conventional searches. We examine instead prospects for detecting higgsino pair production via monojets or mono-…
A charged Higgs boson is a clear signal for an extended Higgs sector, as for example predicted by supersymmetry. Squark mixing can significantly change the pattern of charged-Higgs production and most notably circumvent the chiral suppression for single Higgs production. We evaluate the LHC discovery potential in the light of flavor physics, in the single-Higgs production channel and in association with a hard jet for small and moderate values of tan beta. Thoroughly examining current flavor constraints we find that non-minimal flavor structures can have a sizeable impact, but tend to predict …
We investigate the sensitivity of top pair production to the properties of different Beyond the Standard Model theories embedding a new neutral boson. We include six-fermion decay, and account for the full tree-level Standard Model ttbar interference, with all intermediate particles allowed off-shell. We focus on those observables best suited to the lepton-plus-jets final state at the LHC, and simulate the resulting experimental conditions, including kinematic requirements and top quark pair reconstruction in the presence of missing transverse energy and combinatorial ambiguity in quark-top as…
We examine the ability of LHC experiments to observe jets from squark pair production at the center-of-mass energy E$_{CM}$=10 TeV and 1 fb$^{-1}$ of integrated luminosity. We point out the crucial influence of initial- and final-state radiation on the signal/background discriminating ability of different kinematic variables. The reliable measurements of missing transverse energy and stransverse mass would play a key role in picking out the signal against the background.
We study the sensitivity of top pair production with six-fermion decay at the LHC to the presence and nature of an underlying Z' boson, accounting for full tree-level Standard Model ttbar interference, with all intermediate particles allowed off-shell. We concentrate on the lepton-plus-jets final state and simulate experimental conditions, including kinematic requirements and top quark pair reconstruction in the presence of missing transverse energy and combinatorial ambiguity in jet-top assignment. We focus on the differential mass spectra of the cross section and asymmetry observables, espec…
We analyze the potentiality of the new generation of $e^+e^-$ linear colliders to search for large extra dimensions via the production of fermion pairs in association with Kaluza-Klein gravitons (G), i.e. $e^+e^- \leftarrow f\bar{f}G$. This process leads to a final state exhibiting a significant amount of missing energy in addition to acoplanar lepton or jet pairs. We study in detail this reaction using full tree level contibutions due to the graviton emission and the standard model backgrounds. After choosing the cuts to enhance the signal, we show that a linear collider with a center-of-mass…
We perform a systematic analysis of scalar and vector leptoquark pair production at the Fermilab Tevatron and at the CERN LHC. We evaluate signal expectations and background levels for the processes pp (p ppar) -> 2 jets + e^{+} + e^{-} and 2 jets + e + missing p_T. The Monte Carlo event generator ISAJET is used to simulate the experimental conditions at the current (Sqrt{s}=1.8 TeV, Luminosity=100 pb^{-1}) and upgraded (Luminosity=100 pb^{-1}) Tevatron as well as the LHC (Sqrt{s}=14 TeV, Luminosity=10 fb^{-1}). Depending on the luminosity, and assuming a branching ratio B(LQ -> eq)=0.5, we fi…
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