The impact of ATLAS and CMS single differential top-quark pair measurements at s~(1/2)= 8 TeV on CTEQ-TEA PDFs

By applying the Error PDF Updating Method,we analyze the impact of the absolute and normalized single differential cross-sections for top-quark pair production data from the ATLAS and CMS experiments at the Large Hadron Collider,at a center-of-mass energy of s~(1/2)=8 TeV,on the CT14HERA2 PDFs.We find that the top quark pair single differential distributions provide minor constraints on the CT14HERA2 gluon PDF when the nominal CT14HERA2 inclusive jet production data are included in the fit.Larger constraints on the gluon distribution are present when the jet data are removed(CT14HERA2mJ) and/or when increased weights are given to the top data in the CT14HERA2 fits.The weighted tt data provide significant constraints on the CT14HERA2mJ gluon PDF,which are comparable to those obtained from inclusive jet production data.Furthermore,we examine the top quark mass sensitivity of the top-quark pair single differential distributions.     

Single Production of Doubly Charged Higgs Boson via eγ Collision in Higgs Triplet Model

The Higgs triplet model (HTM) predicts the existence of a pair of doubly charged Higgs bosons H^±± . Single production of H^±± via eγcollision at the next generation e⁺e^- International Linear Collider (ILC) and the Large Hadron electron Collider (LHeC) is considered. The numerical results show that the production cross sections are very sensitive to the neutrino oscillation parameters. Their values for the inverted hierarchy mass spectrum are larger than those for the normal hierarchy mass spectrum at these two kinds of collider experiments. With reasonable values of the relevant free parameters, the possible signals of the doubly charged Higgs bosons predicted by the HTM might be detected in future ILC experiments.     

Prospects for the discovery of 4th family quarks with the ATLAS detector

The pair production of heavy fourth-generation quarks, which are predicted under the hypothesis of flavor democracy, is studied using tree-level Monte Carlo generators and fast detector simulation. Two heavy-quark mass values, 500 and 750 GeV, are considered with the assumption that the fourth family mixes primarily with the two light families. It is shown that a clear signature will be observed in the data collected by the ATLAS detector, after the first year of low-luminosity running at the Large Hadron Collider.     

Direct probes of linearly polarized gluons inside unpolarized hadrons

We show that linearly polarized gluons inside unpolarized hadrons can be directly probed in jet or heavy quark pair production in electron-hadron collisions. We discuss the simplest cos2? asymmetries and estimate their maximal value, concluding that measurements of the unknown linearly polarized gluon distribution in the proton should be feasible in future Electron-Ion Collider or Large Hadron electron Collider experiments. Analogous asymmetries in hadron-hadron collisions suffer from factorization breaking contributions and would allow us to quantify the importance of initial- and final-state interactions.     

Charmed Meson Production in Deep Inelastice+A Scattering at Small-x

Based on the nuclear effects considered in the Glauber-Gribov approach, charmed meson production in high energy deep inelastic e+A scattering is investigated in the color dipole formalism. Using the Peterson fragmentation function and the KLR-AdS/CFT color dipole model, which reasonably well describes the HERA data for the inclusive structure functions at small Bjorken-x, we present the predictive results for the D-meson transverse spectra at EIC and LHeC energies. The theoretical results indicate that the $x$-independence phenomena at very small-x predicted by the KLR-AdS/CFT model are not seen in our calculation.     

Probing small parton densities in ultraperipheral A A and pA collisions at the CERN large Hadron Collider

We calculate photoproduction rates for several hard processes in ultraperipheral proton-lead and lead-lead collisions at the CERN Large Hadron Collider (LHC) with square root of sNN = 8.8 and 5.5 TeV, respectively, which could be triggered in the large LHC detectors. We use ATLAS as an example. The lead ion is treated as a source of (coherently produced) photons with energies and intensities greater than those of equivalent ep collisions at the DESY collider HERA. We find very large rates for both inclusive and diffractive production that will extend the HERA x range by nearly an order of magnitude for similar virtualities. We demonstrate that it is possible to reach the kinematic regime where nonlinear effects are larger than at HERA.     

Consistent treatment of charm evolution in deep inelastic scattering

We present a formulation which allows heavy quark mass effects to be explicitly incorporated in both the coefficient functions and the splitting functions in the parton evolution equations. We obtain a consistent procedure for evolution through the threshold regions for and production in deep inelastic scattering, which allows the prediction of the charm and bottom quark densities. We use the new formulation to perform a next-to-leading order global parton analysis of deep inelastic and related hard scattering data. We find that the optimum fit has . We give predictions for the charm components of the proton structure functions and as functions of and and, in particular, find that is in good agreement with the existing measurements. We examine the range of validity of the photon-gluon fusion model for electroproduction. We emphasize the value of a precision measurement of the charm component at HERA. Received: 12 May 1997 / Revised version: 12 June 1997     

Structure functions at HERA

HERA provides the key facility for the measurement of proton structure functions. Formalism and methods are outlined for the measurement and interpretation of inclusive structure functions, including the use of polarised e ^± beams. The measurement of charm, beauty and photon structure functions is discussed, together with special runs at low proton energy for measurement of the longitudinal structure function. Finally, the functions accessed using polarised beams on polarised targets are indicated.     

Recent results on strangeness,charm and beauty production at HERA

Based on the data collected with the H1 and ZEUS detectors at HERA,recent results on strangeness,charm and beauty production in ep collision are presented.     

Top-quark pairs at high invariant mass: a model-independent discriminator of new physics at the Large Hadron Collider

We study top-quark pair production to probe new physics at the CERN Large Hadron Collider. We propose reconstruction methods for tt[over] semileptonic events and use them to reconstruct the tt[over] invariant mass. The angular distribution of top quarks in their c.m. frame can determine the spin and production subprocess for each new physics resonance. Forward-backward asymmetry and CP-odd variables can be constructed to further delineate the nature of new physics. We parametrize the new resonances with a few generic parameters and show high invariant mass top pair production may provide an early indicator for new physics beyond the standard model.     

Photoproduction of top quarks in peripheral heavy ion collisions

In relativistic heavy ion collisions, top quarks can be produced by photon-gluon fusion when a photon from the Weizs?cker-Williams virtual photon field of one nucleus interacts with a gluon in the other nucleus. Photoproduction with heavy ions at the Large Hadron Collider (LHC) will be the first accessible non-hadronic top production channel. We calculate the photoproduction cross sections, pair mass and top quark rapidity distributions in peripheral lead-lead and oxygen-oxygen collisions. The cross sections are sensitive to the top quark charge and the large- gluon distribution in the nucleus. We find a cross section of 15 pb in oxygen-oxygen collisions, leading to 210 pairs in a one month ( s) LHC run. In pA collisions, the rate is higher, 1100 pairs per month for pO. A comparison of the AA and pA data might allow for a study of gluon shadowing at high Q . Received: 18 May 2001 / Revised version: 13 June 2001 / Published online: 24 August 2001     

Neutral Higgs Boson Pair Production in Standard Model with the Fourth Generation Quarks 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 2×10⁴ neutral Higgs boson pair production events per year if the next generation heavy quarks really exist, while there will be only 2×10³ events produced per year if there are only three families in the SM.     

Large transverse momentum lepton pair production at the Large Hadron Collider

We study the large transverse momentum distribution of lepton pairs produced in heavy-ion collisions, making use of the perturbative QCD. Referring to the calculation of the parton-parton production process into lepton pairs at the Relativistic Heavy Ion Collider (RHIC), the production of lepton pairs at large transverse momentum is extended to the Large Hadron Collider (LHC). The contribution of the parton-parton production process into lepton pairs in Pb-Pb collisions at the LHC is calculated, including the complete processes at large transverse momentum. Lepton pair production with the direct single photon process and the resolved single photon process are considered and confirmed to be significant at the LHC.     

Parton distributions from a global QCD analysis of deep inelastic scattering and lepton-pair production

Parton distribution functions consistent with neutrino and muon deep inelastic scattering as well as Drell-Yan pair production results have been extracted. This analysis incorporates experimental systematic errors which are the dominant errors in recent deep inelastic scattering experiments. The dependence of the results on factors such as kinematic cuts in the data, heavy target corrections, and choice of initial functional form are also explored. The form adopted is motivated by perturbative QCD and particularly useful in exploring the small-x extrapolation of the distributions. This is crucial for studying the range of predictions for Collider, HERA, and SSC/LHC cross sections. Representative distribution function sets are presented in a very compact parametrized form both in the DIS and MS-bar renormalization schemes.This work is partially supported by the National Science Foundation under Grant No. PHY89-05161. This work was also supported by Argonne National Laboratory during the 1988–89 academic year when the author was on Sabbatical leave at the Laboratory from IIT     

Single electrons from heavy-flavor decays in collisions at

The invariant differential cross section for inclusive electron production in p+p collisions at [FORMULA: SEE TEXT] has been measured by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider over the transverse momentum range 0.4相似文献   

Charm structure functions and gluon shadowing effects with the AdS/CFT model

By means of the UGD function extracted from an AdS/CFT inspired saturation model, the charm and bottom structure functions are studied in fixed-order perturbation theory. It is shown that the theoretical results are in good agreement with the recent HERA data. Then, this UGD function is also used to investigate net-kaon rapidity distribution in Au+Au collisions at RHIC energies and the theoretical results fit well to the BRAHMS data. In the end of this paper, we give the predicted results for nuclear charm structure function at very small x where the popular shadowing parameterizations are invalid.     

Measuring the Higgs boson self-coupling at the Large Hadron Collider

Inclusive standard model Higgs boson pair production and subsequent decay to same-sign dileptons via weak gauge W+/- bosons at the CERN Large Hadron Collider (LHC) has the capability to determine the Higgs boson self-coupling, lambda. The large top quark mass limit is found not to be a good approximation for the signal if one wishes to utilize differential distributions in the analysis. We find that it should be possible at the LHC with design luminosity to establish that the standard model Higgs boson has a nonzero self-coupling and that lambda/lambda(SM) can be restricted to a range of 0-3.7 at 95% confidence level if its mass is between 150 and 200 GeV.     

SUSY QCD Residual Effects in pp→bbh Process

If all the supersymmetry particles (sparticles) except a light Higgs boson are too heavy to be directly produced at the Large Hadron Collider (LHC), a possible way to reveal evidence for supersymmetry is through their virtual effects in other processes. We examine such supersymmetric QCD effects in bottom pair production associated with a light Higgs boson at the LHC. We find that if the relevant sparticles (gluinos and squarks) are too heavy to be directly produced well above the TeV scale, they can still have sizable virtual effects in this process. For large tanβ, such residual effects can alter the production rate by over 40 percent,which should be observable in future measurements of this process at the LHC.     

Signal for an extra-dimensional model of flavor at the Large Hadron Collider

In Randall-Sundrum models with gauge bosons and fermions in the extra-dimensional bulk, it is possible to build models of flavor by localizing the fermions in the extra dimension. Since the Higgs boson must be localized at or close to the TeV scale fixed point, heavier fermions must be localized close to this brane. The first Kaluza-Klein excitations of the gauge bosons are also TeV-localized, so they have stronger couplings to heavier fermions leading to tree-level flavor-violating couplings. We investigate the potential of the Large Hadron Collider to observe flavor violation in single top production at very high invariant masses, in addition to the observation of the corresponding t-t[over] resonance. We conclude that the Large Hadron Collider will be able to observe tree-level flavor violation in single top production, probing Kaluza-Klein masses at least as large as 2 TeV, as well as a very interesting region of the parameters.