Search

Charged lepton transverse momenta in the Drell--Yan processes play an important role at the LHC in precision measurements of the Standard Model parameters, such as the W-boson mass and width, their charge asymmetries and sin² ϑW. Therefore, their distributions should be described as accurately as possible by the Monte Carlo event generators. In this paper, we discuss the problem of matching the hard-process kinematics of the Monte Carlo generator WINHAC with the parton-shower kinematics of the PYTHIA 6.4 generator while interfacing these two programs. We show that improper assignment of the quark and antiquark effective momenta in the LO matrix element computations may affect considerably the predicted lepton transverse momenta and even completely reverse their charge asymmetries at the LHC. We propose two matching schemes in which the NLO QCD distributions of the leptonic kinematical variables can be well reproduced by the LO WINHAC generator. [ABSTRACT FROM AUTHOR]

In this paper, the measurement of the fragmentation factor ratio ƒs/ƒd in the LHCb experiment using hadronic decay modes is presented. The relative yields of the three channels B0 → D- π+, B0 → D-K+, B0s → D-S π+ selected from 35pb-1 of data collected in 2010 are used for the analysis. The fragmentation fraction ratio is determined to be ƒs/ƒd = 0.245 ± 0.017stat ± 0.018syst ± 0.018theor. [ABSTRACT FROM AUTHOR]

During 2011, LHCb has collected an integrated luminosity of 1.1 fb-1, giving rise to a large variety of measurements. Amongst these, measurements of CP violation in B decays play a central role. Three highlights are presented in this paper. The evidence for b → u transitions in B± → DK± is obtained, confirming recent BELLE results. The first evidence for direct CP violation in the B0S system is presented and CP violation is observed in the B0 system, using respectively B0S → K- π+ and B0 → K+ π- decays. An unambiguous world leading measurement of the mixing phase φs of the B0S system is obtained by looking at b → cᶜ̄s transitions. [ABSTRACT FROM AUTHOR]

The LHCb experiment at the LHC has collected more than 1 fb-1 of physics data during the first two years of operation at the LHC, reaching one of its most important milestones. This has allowed the experiment to already perform extensive world-class measurements in b and c-physics, in order to probe New Physics Beyond the Standard Model. In this paper, the status and excellent performance of the LHCb experiment are reviewed, focusing the attention on the most important aspects of the operation of the experiment. Moreover, several important physics results are highlighted together with their impact for the full physics program at the LHC. Finally, a description of the upgrade of the detector to collect more than 50 fb -1 starting in 2018 will be also given. [ABSTRACT FROM AUTHOR]

This paper describes the performance of low energy electron reconstruction and identification at ATLAS with proton-proton collisions at a centre of mass energy of 7 TeV produced by the Large Hadron Collider. This study was performed with a sample collected from April to June 2010, corresponding to an integrated luminosity of 78 nb-1. We present the reconstruction of prompt J/ψ mesons decaying into e+e- pairs. These electrons can be used to study the detector performance at low energy, as a complement of higher energy electrons coming from W and Z decays. A sample of ~ 220 J/ψ events can be selected. Their mass values reconstructed with different inputs agree with the values expected from the initial calibration of the ATLAS detector. The kinematics and shower shape distributions (used for identification purpose) have been extracted from the J/ψ data sample and show a good agreement with the simulation. [ABSTRACT FROM AUTHOR]

CP symmetry violation in Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. mixing can be measured in Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. decays to vector-(pseudo)scalar final state. Example of such decay is the Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. which has never been observed so far. The CP symmetry breaking phase of Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. mixing, βs, can be directly extracted from the CP asymmetry observable since the final state is the CP eigenstate. This measurement can complement the one coming from the analysis of the Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. decay. Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. decay is expected to provide the best sensitivity for the βs but the angular distribution analysis is needed to disentangle the admixture of different CP eigenstates of the vector-vector final state. In this paper the CP violation in Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. mesons decays is briefly introduced, the status of current state of βs measurement is presented and finally the analysis of the Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed., as a case study of Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. decay to vector-(pseudo)scalar decay in LHCb experiment, is described. [ABSTRACT FROM AUTHOR]

The year 2010 was the first full year of operation of the Large Hadron Collider (LHC). The Compact Muon Solenoid (CMS) experiment has recorded integrated luminosity of over 43 pb-1 of proton--proton data at center-of-mass energy √s = 7 TeV and 8 μb-1 of lead--lead data at √sNN = 2:76 TeV. In this paper the CMS detector is briefly introduced. Its initial readiness for data taking and status of operation in 2010 is given. The performance of CMS subsystems is shown. Selected measurements from proton--proton and lead--lead runs are described. [ABSTRACT FROM AUTHOR]

This article discusses the recent tests of the Standard Model using pp-collision events at √s = 7 TeV collected with the ATLAS detector at the Large Hadron Collider (LHC) during 2010 data taking period. The paper focuses on measurements of hard and soft sectors of quantum chromodynamics (QCD), a theory describing interactions of quarks and gluons. [ABSTRACT FROM AUTHOR]

In this paper an overall view of the Feasibility Study to host a LAGUNA detector in the Canfranc Underground Laboratory is presented. [ABSTRACT FROM AUTHOR]

The status of the ILC global effort is reviewed starting from the physics motivations and describing the present strategy to build such a machine and its associated detectors. Then assuming that the first significant results from LHC will soon become available, this presentation assumes four different scenarios and discuss the implications for ILC. [ABSTRACT FROM AUTHOR]

The relativistic hydrodynamics together with the single-freeze-out statistical hadronization model is used to describe the mid-rapidity hadron production in ultra-relativistic heavy-ion collisions at RHIC and LHC. At the highest RHIC energy our approach gives a quite satisfactory global description of soft hadronic observables including the HBT radii. With the increased initial energy, from RHIC to LHC, we expect the saturation of the pion elliptic flow and the moderate increase of the correlation radii. [ABSTRACT FROM AUTHOR]

Heavy flavour production at hadron colliders represents a very promising field to test perturbative QCD. The integrated forward--backward asymmetry of the top--antitop quark production is particularly sensitive to any deviation from the standard QCD calculations. The two Tevatron collaborations, CDF and D0, reported a much larger t-quark charge asymmetry than predicted by the theory. We show that the QCD in noncontractible space, where the minimal distance is fixed by weak interactions, enhances the asymmetry by more than a factor of 3 (5) at the parton level in leading order of the coupling for the Tevatron (LHC) center-of-mass energies. This result should not be a surprise since the asymmetry observable directly explores the far ultraviolet sector of the spacelike domain of the Minkowski spacetime. [ABSTRACT FROM AUTHOR]

Phenomenological Tsallis fits to the CMS and ATLAS transverse spectra of charged particles were found to extend for pT from 0.5 to 181 GeV in pp collisions at the LHC at √s = 7 TeV, and for pT from 0.5 to 31 GeV at √s = 0:9 TeV. The simplicity of the Tsallis parametrization and the large range of the fitting transverse momentum raise questions on the physical meaning of the degrees of freedom that enter into the Tsallis distribution or q-statistics. [ABSTRACT FROM AUTHOR]

Single particle momentum spectra are calculated within three microcanonical statistical ensembles, namely, with conserved system energy, system momentum, as well as system energy and momentum. Deviations from the exponential spectrum of the grand canonical ensemble are quantified and discussed. For mean particle multiplicity and temperature, typical for p + p interactions at the LHC energies, the effect of the conservation laws extends to transverse momenta as low as about 3GeV/c. The presented results should be considered as the next step in development of statistical models for particle production in high energy collisions. They can be useful to interpret spectra measured in nuclear collisions at high energies, in particular, their system size dependence. [ABSTRACT FROM AUTHOR]

There is a growing evidence for the anomalously large semileptonic CP asymmetry in the B meson system measured at the Tevatron. The noncontractible space, as an alternative symmetry-breaking mechanism to the Higgs mechanism, can change standard field theoretic calculations of the physical processes mediated through quantum loops for large external momenta or large internal masses. The presence of the W bosons and t quarks in loops of the B meson mixing can enhance the corresponding semileptonic CP asymmetry when the loop integration is up to the universal Lorentz and gauge invariant UV-cutoff?. We show that the enhancement is roughly 13%, thus the possible deviation is measurable at the Tevatron, LHCb, SuperKEKB and SuperB facilities. [ABSTRACT FROM AUTHOR]

A search for the time integrated CP violation in the D0 → h-h+ (h = K,π) decays is presented using 0.62 fb-1 of data collected by the LHCb experiment in 2011. The flavour of the charm meson is determined by the charge of the slow pion in the D*+ → D0 π+ and the D*- → D̄0 π- decays chain. The difference in CP asymmetry between the D0 → K-K+ and the D0 → π -π+, ΔΛCP = ΛCP (K-K+) - ΛCP(*π- π+) is measured to be [-0.82±0.21(stat)±0.11(syst)]%. This differs from the hypothesis of CP conservation by 3.5 standard deviations. An additional search for the time integrated CP violation in the Cabibbo suppressed decay D+ → K-K+π+ is also presented. Here no evidence for CP asymmetry is found using a model independent method. The data used here was collected by the LHCb experiment in 2010 and corresponds to an integrated luminosity of 35 pb-1. The normalized Dalitz plot distributions for the D+ and the D- are compared using two different binning schemes that are sensitive to different manifestations of CP violation. [ABSTRACT FROM AUTHOR]

LHCb is one of the four major experiments at the Large Hadron Collider at CERN and is custom built to look for CP violation and New Physics in rare decays of the B and D mesons. Rare decays that occur via loop diagrams provide a way to probe New Physics at energy scales much higher than can be probed by direct production. In this article, the LHCb analyses of B → μ+μ-, Bd → K*0 μ+μ- and B → Vγ and their results are reported. [ABSTRACT FROM AUTHOR]

During the last decade a number of detailed analyses of flavour observables and of their correlations within more than a dozen specific BSM models have been performed at the TUM. One of the goals of these analyses was to investigate which model is capable of obtaining large mixing induced CP asymmetry in the Bs system, Sψφ, and to find out what this would imply for other flavour observables. In this context, also the rare decays Bs,d → μ+ μ- have been considered. In some models, their branching ratios can be enhanced by orders of magnitude above the SM expectations. The recent data on Sψφ and Bs,d → μ+ μ- from the LHCb put an end to these very optimistic hopes modifying significantly the allowed patterns of deviations from SM predictions for flavour observables in concrete BSM models. We make a first semi-quantitative assessment of the most important modifications in the predictions of the BSM models in question including also recently analyzed models and taking into account the most recent lattice input. Our presentation is dominated by quark flavour observables in Bs,d and K+(K0) meson systems. For some BSM models the LHCb data turned out to be a relief. On the other hand, the SM models with CMFV and MFV models without flavour blind phases appear to have significant difficulties in describing all ΔF = 2 observables in Bs,d and K0 meson systems simultaneously. However, definite conclusions will only be possible when |Vub| and γ will be known from tree level decays with a much better precision and the lattice input will further improve. Finally, we propose to regard the stringent CMFV relations between various observables as standard candles of flavour physics. The pattern of deviations from these relations may help in identifying the correct NP scenario. [ABSTRACT FROM AUTHOR]

I review the latest heavy flavor measurements at RHIC experiments. Measurements from RHIC together with preliminary results from LHC offer us an opportunity to systematically study the sQGP medium properties. In the end, I will outlook a prospective future on precision heavy flavor measurements with detector upgrades at RHIC. [ABSTRACT FROM AUTHOR]

Thanks to its unique capabilities the ALICE experiment can measure the production of identified particles and resonances over a wide momentum range both in pp and Pb--Pb collisions at the LHC. In this report, particle-identification detectors and techniques, as well as achieved performance, are shortly reviewed. The current results on hadron transverse momentum spectra measured in pp collisions at √s = 0.9TeV and 7TeV, and in Pb--Pb collisions at √SNN = 2.76TeV are shown. In particular, proton-- proton results on particle production yields, spectral shapes and particle ratios are presented as a function of the collision energy and compared to previous experiments and commonly-used Monte Carlo models. Particle spectra, yields and ratios in Pb--Pb are measured as a function of the collision centrality and the results are compared with published RHIC data in Au--Au collisions at √SNN = 0:2TeV and predictions for the LHC. [ABSTRACT FROM AUTHOR]

A discussion is presented of results with identified particles at the Large Hadron Collider. Possible deviations from the standard statistical distributions are investigated by considering in detail results obtained using the Tsallis distribution. Matter--antimatter production is discussed within the framework of chemical equilibrium in p--p and heavy ion collisions. [ABSTRACT FROM AUTHOR]

The compact muon solenoid (CMS) detector at the large hadron collider (LHC) is ideal to measure the heavy flavor production, especially, in the dimuon channels in high-multiplicity environment. Compared to the pp data scaled by the number of binary collisions, the yields of prompt and non-prompt J/ψ and ϒ(1S) in Pb-Pb collisions are strongly suppressed at √SNN = 2.76 TeV. In addition, the excited ϒ(2S+3S) states are also suppressed relative to the ground ϒ(1S) state in Pb-Pb collisions. These results consistently indicate a significant medium effect on the heavy-flavor production in heavy-ion collisions at LHC. [ABSTRACT FROM AUTHOR]

We analyze the elliptic flow parameter v2 in Pb+Pb collisions at the LHC energy using a hybrid model in which the evolution of the quark-gluon plasma is described by ideal hydrodynamics and the subsequent hadronic stage by a hadron cascade model. For initial conditions, we employ Monte Carlo versions of the Glauber and the Kharzeev-Levin-Nardi models and compare results with each other. We demonstrate that the differential elliptic flow v2(pT) does not change so much when the collision energy increases, whereas the integrated v2 increases due to the enhancement of mean transverse momentum. [ABSTRACT FROM AUTHOR]

I discuss two topics of importance to phenomenological applications of perturbative high energy evolution. In the first part I discuss a mechanism which leads to long range rapidity and angular correlations in particle production in dense environment. I argue that positive angular correlations are leading 1=Nc effect and may be responsible for the "ridge" structure observed in high multiplicity p-p collisions at LHC. In the second part I describe the setup for calculation of particle production at high transverse momenta and high energy, which fully takes into account the perturbative saturation effects and the leading twist physics. Here I note that recent calculations of inclusive particle production within the high energy approach are missing a term due to inelastic scattering of projectile partons. This piece has to be included in order that the results have proper perturbative limit. Its inclusion is expected to affect strongly the high momentum tail of the particle spectrum. [ABSTRACT FROM AUTHOR]

The CMS soft QCD results in proton-proton collisions at different LHC centre-of-mass energies are reviewed. The first part of the review focuses on the basic kinematic measurements of charged tracks and identified hadrons in minimum bias proton-proton interactions. The second part reports the short- and long-range correlation studies with emphasis on the results exploiting a special trigger specifically developed for large multiplicity events. The third part concentrates on the underlying event phenomenology in jet and Drell-Yan events. Some relevant highlights from the CMS heavy ion program are also discussed. [ABSTRACT FROM AUTHOR]

The transverse structure of the nucleon as probed in hard exclusive processes plays critical role in the understanding of the structure of the underlying event in hard collisions at the LHC, and multiparton interactions. We summarize results of our recent studies of manifestation of transverse nucleon structure in the hard collisions at the LHC, new generalized parton distributions involved in multiparton interactions, presence of parton fluctuations. The kinematic range where interaction of fast partons of the projectile with the target reach black disk regime (BDR) strength is estimated. We demonstrate that in the BDR postselection effect leads to effective fractional energy losses. This effect explains regularities of the single and double forward pion production in dAu collisions at RHIC and impacts on the forward physics in pp collisions at the LHC. [ABSTRACT FROM AUTHOR]

We investigate phenomenology of scalar gluons (sgluons), as appear in e.g. a hybrid N = 1/N = 2 or R-symmetric supersymmetric extension of the Standard Model. Prospects for their discovery at the 7 TeV LHC are discussed. [ABSTRACT FROM AUTHOR]

Arguments for special emergent vacua which generate fermion and weak boson masses are outlined. Limitations and consequences of the concept are discussed. If confirmed, the Australian dipole would give strong support to such a picture. Preliminary support from recent DZero and CDF data is discussed and predictions for LHC are presented. [ABSTRACT FROM AUTHOR]

A process of central exclusive π+π- production in proton-proton collisions and its theoretical description is presented. A possibility of its measurement, during the special low luminosity LHC runs, with the help of the ATLAS central detector for measuring pions and the ALFA stations for tagging the scattered protons is studied. A visible cross-section is estimated to be 21 μb for √s = 7 TeV, which gives over 2000 events for 100 μb-1 of integrated luminosity. Differential distributions in pion pseudorapidities, pion and proton transverse momenta as well as π+π- invariant mass are shown and discussed. [ABSTRACT FROM AUTHOR]

We show that the pT spectra measured in pp collisions at the LHC exhibit geometrical scaling introduced earlier in the context of deep inelastic scattering. We also argue that the onset of geometrical scaling can be seen in nucleus-nucleus collisions at lower RHIC energies. [ABSTRACT FROM AUTHOR]

We overview some of theory and phenomenology aspects of high energy factorization. In the theory part we focus on basic equations of high energy factorization i.e. BFKL, CCFM, BK. In the phenomenology part we focus on forward-central jets correlations at Large Hadron Collider and on production of charged particles in HERA. [ABSTRACT FROM AUTHOR]

We investigate phenomenology of color octet scalars that appear in e.g. the supersymmetric N = 1/N = 2 hybrid model. Prospects for their discovery at the 7 TeV LHC in the tt̄ decay channel are discussed. [ABSTRACT FROM AUTHOR]

New experimental findings and theoretical trends concerning the cosmic ray exotic phenomena are reviewed. Motivation and possibilities of their searches at LHC experiments are discussed. [ABSTRACT FROM AUTHOR]

The observation of long range near side angular correlation (the so-called ridge effect) in pp collisions at the LHC is presented. Data on such correlations in heavy ion collisions at RHIC are shown. Previous informations on angular correlations in high energy pp collisions are critically reviewed. A spectrum of many recent interpretations concerning the effect is presented. [ABSTRACT FROM AUTHOR]

The ALICE and CMS data on the multiplicity distributions are compared with the lower energy data and with the results from the 8.142 version of the PYTHIA MC event generator with two tunings. The ALICE data for moments are used to calculate the factorial cumulants. It is suggested that the data on moments or cumulants are well suited to specify the optimal tuning of the model parameters. [ABSTRACT FROM AUTHOR]

We review basic ideas and recent developments on the determination of the parton substructure of the nucleon in view of applications to precision hadron collider physics. We review the way information on PDFs is extracted from the data exploiting QCD factorisation, and discuss the current main two approaches to parton determination (Hessian and Monte Carlo) and their use in conjunction with different kinds of parton parameterisation. We summarise the way different physical processes can be used to constrain different aspects of PDFs. We discuss the meaning, determination and use of parton uncertainties. We briefly summarise the current state of the art on PDFs for LHC physics. [ABSTRACT FROM AUTHOR]

The hybrid N = 1/N = 2 supersymmetric model predicts scalar gluons (sgluons) as SUSY partners of the Dirac gluino. Their strikingly distinct phenomenology at the CERN Large Hadron Collider is discussed. [ABSTRACT FROM AUTHOR]

The shell structure of the nucleus implies the existence of magic numbers. Since several years many indications have been accumulated, theoretically as well as through experiments at various laboratories around the world, that if one moves away from stability, the location of the magic numbers shifts as an inescapable consequence of the evolving nature of the nuclear force itself. In this respect, it is the balance between the tensor and spin-orbit components that seems particularly instrumental. Illustrative examples from recent experiments at Ganil, at the neutron-rich and proton-rich side of the nuclear chart for N or Z equal 20 or 28, will be presented here. [ABSTRACT FROM AUTHOR]

In these lecture notes we review some prospect for the upcoming LHC experiments in view of the exploration of the Standard Model (SM) or its minimal Supersymmetric extension (MSSM). We focus on some theoretical aspects concerning the Higgs sector of the two models. We give results for the precision observables MW and mt and their impact on the indirect determination of the Higgs sector. We furthermore review the prospects for the direct measurements in the SM and MSSM Higgs sector. [ABSTRACT FROM AUTHOR]

The Large Hadron Collider LHC will start operating, at CERN, Geneva, Switzerland in 2008. CMS and ATLAS are the two general purpose detectors that will collect data at the LHC. A brief overview of the ATLAS and CMS detector is given, followed by the status of the construction, installation and commissioning. Next, a quick tour on what could be the first physics measurements and search results for new physics at the LHC will be given. [ABSTRACT FROM AUTHOR]