Effect of Hadron Contamination on Dielectron Signal Reconstruction in Heavy Flavor Production Measurements

Dielectron signal reconstruction is an important tool for heavy flavor measurements because of its trigger feasibility and its relatively straightforward particle identification process. However, in the case of time projection chamber detectors, some hadron contamination is unavoidable, even if additional means are used to improve the particle identification process. In this paper, we investigate the effects of hadron (protons, pions, and kaons) contamination on the dielectron signal reconstruction process in the measurement of <math id="M1" xmlns="http://www.w3.org/1998/Math/MathML"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> and electrons from heavy flavor hadron decays

R-parity violating chargino decays at the LHC

Supersymmetric models with R-parity violation (RPV) have become more popular following the lack of any excess of missing energy events at the 8 TeV LHC. To identify such models, the suggested searches generally rely on the decay products of the (effectively) lightest supersymmetric particle (LSP), with signals that depend on the identity of the LSP and the relevant RPV operators. Here we look at the prospects for detecting RPV chargino decays at the LHC and find substantial patches of parameter space in the Minimal Supersymmetric Standard Model with possibly spectacular signatures, such as three charged-lepton resonances

Feasibility Studies for Quarkonium Production at a Fixed-Target Experiment Using the LHC Proton and Lead Beams (AFTER@LHC)

Being used in the fixed-target mode, the multi-TeV LHC proton and lead beams allow for studies of heavy-flavour hadroproduction with unprecedented precision at backward rapidities, far negative Feynman- <math id="M1" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>x</mi></mrow></math> , using conventional detection techniques. At the nominal LHC energies, quarkonia can be studied in detail in <math id="M2" xmlns="http://www.w3.org/1998/Math/MathML"><mi>p</mi><mo>+</mo><mi>p</mi></math> , <math id="M3" xmlns="http://www.w3.org/1998/Math/MathML"><mi>p</mi><mo>+</mo><mi>d</mi></math> , and <math id="M4" xmlns="http://www.w3.org/1998/Math/MathML"><mi>p</mi><mo>+</mo><mi>A</mi></math> collisions at <math id="M5" xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><msub><mrow><mi>s</mi></mrow><mrow><mtext>N</mtext><mtext>N</mtext></mrow></msub></msqrt><mo>≃</mo><mn>115</mn></math>  GeV and in Pb + <math id="M6" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>p</mi></mrow></math> and Pb + <math id="M7" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>A</mi></mrow></math> collisions at <math id="M8" xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><msub><mrow><mi>s</mi></mrow><mrow><mtext>N</mtext><mtext>N</mtext></mrow></msub></msqrt><mo>≃</mo><mn>72</mn></math>  GeV with luminosities roughly equivalent to that of the collider mode that is up to 20 fb−1 yr−1 in <math id="M9" xmlns="http://www.w3.org/1998/Math/MathML"><mi>p</mi><mo>+</mo><mi>p</mi></math> and <math id="M10" xmlns="http://www.w3.org/1998/Math/MathML"><mi>p</mi><mo>+</mo><mi>d</mi></math> collisions, up to 0.6 fb−1 yr−1 in <math id="M11" xmlns="http://www.w3.org/1998/Math/MathML"><mi>p</mi><mo>+</mo><mi>A</mi></math> collisions, and up to 10 nb−1 yr−1 in Pb + <math id="M12" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>A</mi></mrow></math> collisions. In this paper, we assess the feasibility of such studies by performing fast simulations using the performance of a LHCb-like detector

Parton distribution functions at LO, NLO and NNLO with correlated uncertainties between orders

Sets of parton distribution functions (PDFs) of the proton are reported for the leading (LO), next-to-leading (NLO) and next-to-next-to-leading-order (NNLO) QCD calculations. The parton distribution functions are determined with the HERAFitter program using the data from the HERA experiments and preserving correlations between uncertainties for the LO, NLO and NNLO PDF sets. The sets are used to study cross-section ratios and their uncertainties when calculated at different orders in QCD. A reduction of the overall theoretical uncertainty is observed if correlations between the PDF sets are taken into account for the ratio of WW di-boson to Z boson production cross sections at the LHC

Physics at the e+e- linear collider

A comprehensive review of physics at an e+e- linear collider in the energy range of s=92  GeV–3 TeV is presented in view of recent and expected LHC results, experiments from low-energy as well as astroparticle physics. The report focusses in particular on Higgs-boson, top-quark and electroweak precision physics, but also discusses several models of beyond the standard model physics such as supersymmetry, little Higgs models and extra gauge bosons. The connection to cosmology has been analysed as well

Charge symmetry breaking in dd→He4π0 with WASA-at-COSY

Charge symmetry breaking (CSB) observables are a suitable experimental tool to examine effects induced by quark masses on the nuclear level. Previous high precision data from TRIUMF and IUCF are currently used to develop a consistent description of CSB within the framework of chiral perturbation theory. In this work the experimental studies on the reaction dd→He4π0 have been extended towards higher excess energies in order to provide information on the contribution of p -waves in the final state. For this, an exclusive measurement has been carried out at a beam momentum of pd=1.2 GeV/c using the WASA-at-COSY facility. The total cross section amounts to σtot=(118±18stat±13sys±8ext) pb and first data on the differential cross section are consistent with s -wave pion production

Odd and even partial waves of ηπ− and η′π− in π−p→η(′)π−p at 191 GeV/c

Exclusive production of ηπ− and η′π− has been studied with a 191 GeV/c π− beam impinging on a hydrogen target at COMPASS (CERN). Partial-wave analyses reveal different odd/even angular momentum ( L ) characteristics in the inspected invariant mass range up to 3 GeV/c2 . A striking similarity between the two systems is observed for the L=2,4,6 intensities (scaled by kinematical factors) and the relative phases. The known resonances a2(1320) and a4(2040) are in line with this similarity. In contrast, a strong enhancement of η′π− over ηπ− is found for the L=1,3,5 waves, which carry non- qq¯ quantum numbers. The L=1 intensity peaks at 1.7 GeV/c2 in η′π− and at 1.4 GeV/c2 in ηπ− , the corresponding phase motions with respect to L=2 are different

Measurement of azimuthal hadron asymmetries in semi-inclusive deep inelastic scattering off unpolarised nucleons

Spin-averaged asymmetries in the azimuthal distributions of positive and negative hadrons produced in deep inelastic scattering were measured using the CERN SPS longitudinally polarised muon beam at 160 GeV/c and a 6 LiD target. The amplitudes of the three azimuthal modulations cos⁡ϕh , cos⁡2ϕh and sin⁡ϕh were obtained binning the data separately in each of the relevant kinematic variables x , z or pTh and binning in a three-dimensional grid of these three variables. The amplitudes of the cos⁡ϕh and cos⁡2ϕh modulations show strong kinematic dependencies both for positive and negative hadrons

Spin alignment and violation of the OZI rule in exclusive ω and ϕ production in pp collisions

Exclusive production of the isoscalar vector mesons ω and ϕ is measured with a 190 GeV/c proton beam impinging on a liquid hydrogen target. Cross section ratios are determined in three intervals of the Feynman variable xF of the fast proton. A significant violation of the OZI rule is found, confirming earlier findings. Its kinematic dependence on xF and on the invariant mass MpV of the system formed by fast proton pfast and vector meson V is discussed in terms of diffractive production of pfastV resonances in competition with central production. The measurement of the spin density matrix element ρ00 of the vector mesons in different selected reference frames provides another handle to distinguish the contributions of these two major reaction types. Again, dependences of the alignment on xF and on MpV are found. Most of the observations can be traced back to the existence of several excited baryon states contributing to ω production which are absent in the case of the ϕ meson. Removing the low-mass MpV resonant region, the OZI rule is found to be violated by a factor of eight, independently of xF