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.     

Lower limit on dark matter production at the CERN Large Hadron Collider

We evaluate the prospects for finding evidence of dark matter production at the CERN Large Hadron Collider. We consider weakly interacting massive particles (WIMPs) and superWIMPs and characterize their properties through model-independent parametrizations. The observed relic density then implies lower bounds on dark matter production rates as functions of a few parameters. For WIMPs, the resulting signal is indistinguishable from background. For superWIMPs, however, this analysis implies significant production of metastable charged particles. For natural parameters, these rates may far exceed Drell-Yan cross sections and yield spectacular signals.     

Hadron production at large transverse momentum and QCD

The predictions of a QCD-based hardscattering model for large p_T hadronic processes are investigated. Not only quark-quark scattering but all contributions in lowest order are considered. At low x_T, gluon-gluon and quark-gluon scattering are found to dominate the quark-quark term. At present energies the QCD predictions lie below the data but already come very close at the highest ISR energy. Predictions for higher p_T values and higher energies are made.     

Diffractive Higgs boson production at the Fermilab Tevatron and the CERN Large Hadron Collider

Improved possibilities to find the Higgs boson in diffractive events, having less hadronic activity, depend on whether the cross section is large enough. Based on the soft color interaction models that successfully describe diffractive hard scattering at DESY HERA and the Fermilab Tevatron, we find that only a few diffractive Higgs events may be produced at the Tevatron, but we predict a substantial rate at the CERN Large Hadron Collider.     

Precision study of W~-W~+H production including parton shower effects at CERN Large Hadron Collider

The precision study of W~-W~+H production with subsequent W~±→l~±_v_l~((-)) and H→bb decays at the Large Hadron Collider(LHC) aids in the investigation of Higgs gauge couplings and the search for new physics beyond the standard model.In this study,we calculate the shower-matched next-to-leading order QCD and electroweak(EW)corrections from the qq annihilation and photon-induced channels to the W~-W~+H production at the 14 TeV LHC.We deal with the subsequent decays of Higgs and W~± bosons by adopting the MADSPIN method.Both the integrated cross section and some kinematic distributions of W~±,H,and their decay products are provided.We find that the QCD correction significantly enhances the leading-order differential cross section,while the EW correction from the qq annihilation channel obviously suppresses it,especially in the high energy phase-space region,due to the Sudakov effect.The qy-and yy-induced relative corrections are positive and insensitive to the transverse momenta of W~±,H,and their decay products.These photon-induced corrections compensate the negative qq-initiated EW correction,and become the dominant EW contribution as the increment of the pp colliding energy.The parton shower(PS) effects on kinematic distributions are not negligible.The relative PS correction to the b-jet transverse momentum distribution can exceed 100% in the high p_(T,b) region.Moreover,we investigate the scale and PDF uncertainties,and find that the theoretical error of the QCD+EW+qγ+γγ-corrected integrated cross section mainly originates from the renormalization scale dependence of the QCD correction.     

Large transverse momentum particle production in αα and pp collisions at the CERN ISR

The production of charged hadrons with high p_T in αα collisions at √s=126 GeV and pp collisions at √s=31 and 63 GeV is compared, and the structure of the events associated with the high-pT particles is studied. The probability of finding associated particles close to the trigger particle increases strongly between √s=31 and 63 GeV for pp collisions. For p_T>2.5GeV/c the αα/pp cross section ratio at the same energy per nucleon is measured to be 18.7 ± 2.0, to be compared with A² = 16, and a higher associated multiplicity is observed for αα.     

Pion production at large transverse momentum

A constituent interchange model is used to give a natural explanation of the observed energy dependence of ISR data for π° production at 90°. It is predicted that at large fixed p_T and sufficiently high energy the cross section will become constant, with a p_T dependence of (p_T²)^?2.5. It is also tentatively suggested that the e⁺e^? annihilation structure function $\text{ν}\text{W}{}_2$ should behave like ω^?1.5 near ω = 0.     

Particle production at large transverse momentum

From a simple fragmentation approach to inelastic production at large fixed angles, we obtain an inclusive cross-section which falls as an inverse power of large transverse momentum p_T and which scales according to (p_T/√s), both consistent with ISR data. Predictions for charge ratios and associated multiplicities are also presented and compared with available data.     

Black holes in many dimensions at the CERN Large Hadron Collider: testing critical string theory

We consider black hole production at the CERN Large Hadron Collider (LHC) in a generic scenario with many extra dimensions where the standard model fields are confined to a brane. With approximately 20 dimensions the hierarchy problem is shown to be naturally solved without the need for large compactification radii. We find that in such a scenario the properties of black holes can be used to determine the number of extra dimensions, . In particular, we demonstrate that measurements of the decay distributions of such black holes at the LHC can determine if is significantly larger than 6 or 7 with high confidence and thus can probe one of the critical properties of string theory compactifications.     

Landscape of supersymmetric particle mass hierarchies and their signature space at the CERN Large Hadron Collider

The minimal supersymmetric standard model with soft breaking has a large landscape of supersymmetric particle mass hierarchies. This number is reduced significantly in well-motivated scenarios such as minimal supergravity and alternatives. We carry out an analysis of the landscape for the first four lightest particles and identify at least 16 mass patterns, and provide benchmarks for each. We study the signature space for the patterns at the CERN Large Hadron Collider by analyzing the lepton+ (jet> or =2) + missing P{T} signals with 0, 1, 2, and 3 leptons. Correlations in missing P{T} are also analyzed. It is found that even with 10 fb{-1} of data a significant discrimination among patterns emerges.     

Chiral electric field in relativistic heavy-ion collisions at energies available at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider

It has been proposed that electric fields may lead to chiral separation in quark-gluon plasma(QGP).This is called the chiral electric separation effect.The strong electromagnetic field and the QCD vacuum can both be completely produced in off-central nuclear-nuclear collision.We use the Woods-Saxon nucleon distribution to calculate the electric field distributions of off-central collisions.The chiral electric field spatial distribution at Relativistic Heavy-Ion Collider(RHIC) and Large Hadron Collider(LHC) energy regions are systematically studied in this paper.The dependence of the electric field produced by the thermal quark in the central position with different impact parameters on the proper time with different collision energies in the RHIC and LHC energy regions are studied in this paper.