This paper presents a search for the t-channel exchange of an R-parity violating scalar top quark (\={t}) in the emu continuum using 2.1/fb of data collected by the ATLAS detector in sqrt(s) = 7 TeV pp collisions at the Large Hadron Collider. Data are found to be consistent with the expectation from the Standard Model backgrounds. Limits on R-parity-violating couplings at 95% C.L. are calculated as a function of the scalar top mass (m_{\={t}}). The upper limits on the production cross section for pp->emuX, through the t-channel exchange of a scalar top quark, ranges from 170 fb for m_{\={t}}=95 GeV to 30 fb for m_{\={t}}=1000 GeV.
The observed E-MU invariant mass distribution plus SM background and signal predicitons for a n stop mass of 95 GeV.
Information about the signal samples used.
The ratios of the observed and expected upper cross section limits to the theoretical cross sections as a function of the scalar top mass.
The differential production cross section of electrons from semileptonic heavy-flavour hadron decays has been measured at mid-rapidity ($|y| < 0.5$) in proton-proton collisions at $\sqrt{s} = 7$ TeV with ALICE at the LHC. Electrons were measured in the transverse momentum range 0.5 $<p_{\rm T}<$ 8 GeV/$c$. Predictions from a fixed order perturbative QCD calculation with next-to-leading-log resummation agree with the data within the theoretical and experimental uncertainties.
Double differential cross section for heavy-flavour electron production as a function of transverse momentum. The systematic error does not include the error on the Luminosity (3.5%).
The Lambda(b) differential production cross section and the cross section ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7 TeV using data collected by the CMS experiment at the LHC. The measurements are based on Lambda(b) decays reconstructed in the exclusive final state J/Psi Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and Lambda to proton pion, using a data sample corresponding to an integrated luminosity of 1.9 inverse femtobarns. The product of the cross section times the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls faster than that of b mesons. The measured value of the cross section times the branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06 +/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are statistical and systematic, respectively.
The measured Lambda/B integrated cross section and the ratio of anti-Lambda/B to Lambda/B cross sections.
The measured Lambda/B differential cross section and the ratio of anti-Lambda/B to Lambda/B cross sections as a function of the Lambda/B transverse momentum The second and third systematic errors on the cross sections are the common luminosity and branching fraction uncertainties respectively.
The measured Lambda/B differential cross section and the ratio of anti-Lambda/B to Lambda/B cross sections as a function of the Lambda/B absolute rapidity. The second and third systematic errors on the cross sections are the common luminosity and branching fraction uncertainties respectively.
The production of $J/\psi$ mesons accompanied by open charm, and of pairs of open charm hadrons are observed in pp collisions at a centre-of-mass energy of 7 TeV using an integrated luminosity of $355pb^{-1}$ collected with the LHCb detector. Model independent measurements of absolute cross-sections are given together with ratios to the measured $J/\psi$ and open charm cross-sections. The properties of these events are studied and compared to theoretical predictions.
Normalized differential cross-section $d\ln\sigma(pp\rightarrow J/\psi D^0 X)/dp_T(J/\psi)$ for $2<y(J/\psi)<4$, $p_T(J/\psi)<12$ GeV/$c$, $2<y(D^0)<4$, $3<p_T(D^0)<12$ GeV/$c$ region.
Normalized differential cross-section $d\ln\sigma(pp\rightarrow J/\psi D^+ X)/dp_T(J/\psi)$ for $2<y(J/\psi)<4$, $p_T(J/\psi)<12$ GeV/$c$, $2<y(D^+)<4$, $3<p_T(D^+)<12$ GeV/$c$ region.
Normalized differential cross-section $d\ln\sigma(pp\rightarrow J/\psi D_s^+ X)/dp_T(J/\psi)$ for $2<y(J/\psi)<4$, $p_T(J/\psi)<12$ GeV/$c$, $2<y(D_s^+)<4$, $3<p_T(D_s^+)<12$ GeV/$c$ region.
A search for production of supersymmetric particles in final states containing jets, missing transverse momentum, and at least one hadronically decaying tau lepton is presented. The data were recorded by the ATLAS experiment in sqrt(s) = 7 TeV proton-proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation was observed in 2.05 fb-1 of data. The results are interpreted in the context of gauge mediated supersymmetry breaking models with Mmess = 250 TeV, N5 = 3, mu > 0, and Cgrav = 1. The production of supersymmetric particles is excluded at 95% C.L. up to a supersymmetry breaking scale Lambda = 30 Tev, independent of tan(beta), and up to Lambda = 43 TeV for large tan(beta).
Distribution of the missing transverse energy before final selection requirement on the effective mass. Tabulated are the observed Data events, the Standard Model predictions and the expected rates for two signal scenarios with Lambda=30TeV / tan(beta) = 20 and Lambda=40GeV / tan(beta)=30 respectively.
Distribution of the tau pt before final selection requirement on the effective mass. Tabulated are the observed Data events, the Standard Model predictions and the expected rates for two signal scenarios with Lambda=30TeV / tan(beta) = 20 and Lambda=40GeV / tan(beta)=30 respectively.
Distribution of the effective mass before final selection requirement on the effective mass. Tabulated are the observed Data events, the Standard Model predictions and the expected rates for two signal scenarios with Lambda=30TeV / tan(beta) = 20 and Lambda=40GeV / tan(beta)=30 respectively.
The prompt production of charmonium $\chi_{c}$ and $J/\psi$ states is studied in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=7$ TeV at the Large Hadron Collider. The $\chi_{c}$ and $J/\psi$ mesons are identified through their decays $\chi_{c}\rightarrow J/\psi \gamma$ and $J/\psi\rightarrow \mu^+\mu^-$ using 36 pb$^{-1}$ of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for $\chi_{c}$ and $J/\psi$, $\sigma (\chi_{c}\rightarrow J/\psi \gamma)/ \sigma (J/\psi)$, is determined as a function of the $J/\psi$ transverse momentum in the range $2 < p_{\mathrm T}^{J/\psi} < 15$ GeV/$c$. The results are in excellent agreement with next-to-leading order non-relativistic expectations and show a significant discrepancy compared with the colour singlet model prediction at leading order, especially in the low $p_{\mathrm T}^{J/\psi}$ region.
Ratio of cross sections for Chi_c to J/psi production in bins of J/psi transverse momentum over the J/psi rapidity range 2.0 to 4.5. The maximum uncertainties from the unknown Chi_c polarizations shown separately.
A measurement of the multi-strange $\Xi^-$ and $\Omega^-$ baryons and their antiparticles by the ALICE experiment at the CERN Large Hadron Collider (LHC) is presented for inelastic proton-proton collisions at centre of mass energy of 7 TeV. The transverse momentum ($p_{\rm T}$) distributions were studied at mid-rapidity (|y| < 0.5) in the range of 0.6 < $p_{\rm T}$ < 8.5 GeV/$c$ for $\Xi^-$ and $\Xi^+$ baryons, and in the range of 0.8 < $p_{\rm T}$ < 5 GeV/$c$ for $\Omega^-$ and $\Omega^+$. Baryons and antibaryons were measured as separate particles and we find that the baryon to antibaryon ratio of both particle species is consistent with unity over the entire range of the measurement. The statistical precision of the current LHC data has allowed us to measure a difference between the mean $p_{\rm T}$ of $\Xi^-$ ($\Xi^+$) and $\Omega^-$ ($\Omega^+$). Particle yields, mean $p_{\rm T}$, and the spectra in the intermediate $p_{\rm T}$ range are not well described by the PYTHIA Perugia 2011 tune Monte Carlo event generator, which has been tuned to reproduce the early LHC data. The discrepancy is largest for $\Omega^-$ ($\Omega^+$). This PYTHIA tune approaches the $p_{\rm T}$ spectra of $\Xi^-$ and $\Xi^+$ baryons below $p_{\rm T}$ < 0.85 GeV/$c$ and describes the $\Xi^-$ and $\Xi^+$ spectra above $p_{\rm T}$ > 6.0 GeV/$c$. We also illustrate the difference between the experimental data and model by comparing the corresponding ratios of ($\Omega^{-}+\Omega^+)/(\Xi^-+\Xi^+)$ as a function of transverse mass.
pT differential yield for OMEGA- and OMEGABAR+ production in P-P collisions in the rapidity range -5 to 0.5. Note: there is no division by (2.pi.pT) included in the ordinate values.
pT differential yield for XI- and XIBAR+ production in P-P collisions in the rapidity range -5 to 0.5. Note: there is no division by (2.pi.pT) included in the ordinate values.
Ratio of (OMEGA-+OMEGABAR+) to (XI-+XIBAR+) production as a function of MT-M0. Note: the binning in (mT-m0) is the consequence of the pT binning of the Omega spectra.
A search for the weak production of charginos and neutralinos into final states with three electrons or muons and missing transverse momentum is presented. The analysis uses 2.06 fb^-1 of sqrt(s) = 7 TeV proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with standard model expectations in two signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric and simplified models. For the simplified models, degenerate lightest chargino and next-to-lightest neutralino masses up to 300 GeV are excluded for mass differences from the lightest neutralino up to 300 GeV.
Transverse momentum distribution for the first leading lepton for events in the SR1 signal region for DATA and SM predictions.
Transverse momentum distribution for the first leading lepton for events in the SR2 signal region for DATA and SM predictions.
Transverse momentum distribution for the second leading lepton for events in the SR1 signal region for DATA and SM predictions.
A measurement of the underlying event (UE) activity in proton-proton collisions at a center-of-mass energy of 7 TeV is performed using Drell--Yan events in a data sample corresponding to an integrated luminosity of 2.2 inverse femtobarns, collected by the CMS experiment at the LHC. The activity measured in the muonic final state (q q-bar to opposite-sign muons) is corrected to the particle level and compared with the predictions of various Monte Carlo generators and hadronization models. The dependence of the UE activity on the dimuon invariant mass is well described by PYTHIA and HERWIG++ tunes derived from the leading jet/track approach, illustrating the universality of the UE activity. The UE activity is observed to be independent of the dimuon invariant mass in the region above 40 GeV, while a slow increase is observed with increasing transverse momentum of the dimuon system. The dependence of the UE activity on the transverse momentum of the dimuon system is accurately described by MADGRAPH, which simulates multiple hard emissions.
Toward $N_\text{chg}$ density vs $p_\perp^{\mu\mu}$.
Transverse $N_\text{chg}$ density vs $p_\perp^{\mu\mu}$.
Away $N_\text{chg}$ density vs $p_\perp^{\mu\mu}$.
A study of dijet production in proton-proton collisions was performed at sqrt(s) = 7 TeV for jets with pt > 35 GeV and abs(y) < 4.7 using data collected with the CMS detector at the LHC in 2010. Events with at least one pair of jets are denoted as 'inclusive'. Events with exactly one pair of jets are called 'exclusive'. The ratio of the cross section of all pairwise combinations of jets to the exclusive dijet cross section as a function of the rapidity difference between jets abs(Delta(y)) is measured for the first time up to abs(Delta(y)) = 9.2. The ratio of the cross section for the pair consisting of the most forward and the most backward jet from the inclusive sample to the exclusive dijet cross section is also presented. The predictions of the Monte Carlo event generators PYTHIA6 and PYTHIA8 agree with the measurements. In both ratios the HERWIG++ generator exhibits a more pronounced rise versus abs(Delta(y)) than observed in the data. The BFKL-motivated generators CASCADE and HEJ+ARIADNE predict for these ratios a significantly stronger rise than observed.
Inclusive to exclusive dijet production ratio.
Mueller-Navelet to exclusive dijet production ratio.
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