Search

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]

In this paper, a measurement of ? polarization in W? ?? decays is presented. It is measured from the energies of the decay products in hadronic ? decays with a single final state charged particle. The data, corresponding to an integrated luminosity of 24 pb, were collected by the ATLAS experiment at the Large Hadron Collider in 2010. The measured value of the ? polarization is ${P_{\tau}}= -1.06 \pm0.04\ (\mathrm{stat})\;^{+0.05}_{-0.07}\ (\mathrm{syst})$, in agreement with the Standard Model prediction, and is consistent with a physically allowed 95 % CL interval [?1,?0.91]. Measurements of ? polarization have not previously been made at hadron colliders. [ABSTRACT FROM AUTHOR]

Abstract: TheATLASPixel Detectoristhe innermost detectoroftheATLASexperimentattheLarge Hadron CollideratCERN, providing high-resolution measurements of charged particle tracks in the high radiation environment close to the collision region. This capability is vital for the identification and measurement of proper decay times of long-lived particles such as b-hadrons, and thus vital for theATLASphysics program. The detector provides hermetic coverage with three cylindrical layers and three layers of forward and backward pixel detectors. It consists of approximately 80 million pixels that are individually read out via chipsbump-bonded to 1744 n-on-n silicon substrates. In this paper results from the successful operation of the Pixel Detector at the LHC will be presented, including calibration procedures, timing optimization and detector performance. The detector performance is excellent: approximately 97% of the pixels are operational, noise occupancyand hit efficiency exceed the design specification, and a good alignment allows high quality track resolution. [Copyright &y& Elsevier]

A search for supersymmetric particles in final states with zero, one, and two leptons, with and without jets identified as originating from b-quarks, in 4.7 fb of $\sqrt{s}=7\mbox{ TeV}$ pp collisions produced by the Large Hadron Collider and recorded by the ATLAS detector is presented. The search uses a set of variables carrying information on the event kinematics transverse and parallel to the beam line that are sensitive to several topologies expected in supersymmetry. Mutually exclusive final states are defined, allowing a combination of all channels to increase the search sensitivity. No deviation from the Standard Model expectation is observed. Upper limits at 95 % confidence level on visible cross-sections for the production of new particles are extracted. Results are interpreted in the context of the constrained minimal supersymmetric extension to the Standard Model and in supersymmetry-inspired models with diverse, high-multiplicity final states. [ABSTRACT FROM AUTHOR]

The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of $\sqrt{s} = 900~\mbox{GeV}$ and 7 TeV collected during 2009 and 2010. Then, using the decay of K and ? particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5 % for central isolated hadrons and 1-3 % for the final calorimeter jet energy scale. [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]

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 discuss the implementation of the 'minimal' type III seesaw model, i.e. with one fermionic triplet, in FeynRules/MadGraph. This is the first step in order to realize a real study of LHC data recorded in the LHC detectors. With this goal in mind, we comment on the possibility of discovering this kind of new physics at the LHC running at 7 TeV with a luminosity of few fb. [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]