The $p_{\rm T}$-differential production cross section of prompt $\Lambda_{\rm c}^+$ charmed baryons was measured with the ALICE detector at the Large Hadron Collider (LHC) in pp collisions at $\sqrt{s} = 7$ TeV and in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV at midrapidity. The $\Lambda_{\rm c}^+$ and ${\overline{\Lambda}}_{\rm c}^-$ were reconstructed in the hadronic decay modes $\Lambda_{\rm c}^+\rightarrow {\rm p}{\rm K^-}\pi^+$, $\Lambda_{\rm c}^+\rightarrow {\rm p}{\rm K_{\rm S}^0}$ and in the semileptonic channel $\Lambda_{\rm c}^+\rightarrow {\rm e^+}\nu_{\rm e}\Lambda$ (and charge conjugates). The measured values of the $\Lambda_{\rm c}^+/{\rm D_0}$ ratio, which is sensitive to the c-quark hadronisation mechanism, and in particular to the production of baryons, are presented and are larger than those measured previously in different colliding systems, centre-of-mass energies, rapidity and $p_{\rm T}$ intervals, where the $\Lambda_{\rm c}^+$ production process may differ. The results are compared with the expectations obtained from perturbative Quantum Chromodynamics calculations and Monte Carlo event generators. Neither perturbative QCD calculations nor Monte Carlo models reproduce the data, indicating that the fragmentation of heavy-flavour baryons is not well understood. The first measurement at the LHC of the $\Lambda_{\rm c}^+$ nuclear modification factor, $R_{\rm pPb}$, is also presented. The $R_{\rm pPb}$ is found to be consistent with unity and with that of D mesons within the uncertainties, and consistent with a theoretical calculation that includes cold nuclear matter effects and a calculation that includes charm quark interactions with a deconfined medium.
Prompt $\Lambda_{\rm {c}}^{+}$ baryon $p_{\rm {T}}$-differential cross section (average among different decay modes and analyses) in pp collisions at $\sqrt{s} = 7$ TeV in the rapidity interval $|y|<0.5$.
Prompt $\Lambda_{\rm {c}}^{+}$ baryon $p_{\rm {T}}$-differential cross section (average among different decay modes and analyses) in p-Pb collisions at $\sqrt{s_{\rm {NN}}} = 5.02$ TeV in the rapidity interval $-0.96 \lt y \lt 0.04$.
The $\Lambda_{\rm {c}}^{+}$/${\rm D}^{0}$ ratio measured in pp collisions at $\sqrt{s} = 7$ TeV in the rapidity interval $|y|<0.5$ as a function of $p_{\rm {T}}$.
Results are reported from a search for physics beyond the standard model in proton-proton collisions at a center-of-mass energy of $\sqrt{s} = $ 13 TeV. The search uses a signature of a single lepton, large jet and bottom quark jet multiplicities, and high sum of large-radius jet masses, without any requirement on the missing transverse momentum in an event. The data sample corresponds to an integrated luminosity of 35.9 fb$^{-1}$ recorded by the CMS experiment at the LHC. No significant excess beyond the prediction from standard model processes is observed. The results are interpreted in terms of upper limits on the production cross section for $R$-parity violating supersymmetric extensions of the standard model using a benchmark model of gluino pair production, in which each gluino decays promptly via $ {\mathrm{\widetilde{g}}} \rightarrow \mathrm{t} \mathrm{b} \mathrm{s} $. Gluinos with a mass below 1610 GeV are excluded at 95% confidence level.
Figure 8. Observed cross section upper limits at 95% CL for a model of gluino pair production with gluino->tbs compared to the gluino pair production cross section.
Figure 8. Expected limits at 95% CL and their ±1 sigma variations for a model of gluino pair production with gluino->tbs compared to the gluino pair production cross section.
Figure 8. Expected limits at 95% CL and their ±2 sigma variations for a model of gluino pair production with gluino->tbs compared to the gluino pair production cross section.
The nuclear modification factors of J/$\psi$ and $\psi$(2S) mesons are measured in PbPb collisions at a centre-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}} =$ 5.02 TeV. The analysis is based on PbPb and pp data samples collected by CMS at the LHC in 2015, corresponding to integrated luminosities of 464 $\mu$b$^{-1}$ and 28 pb$^{-1}$, respectively. The measurements are performed in the dimuon rapidity range of $|y| <$ 2.4 as a function of centrality, rapidity, and transverse momentum (p$_\mathrm{T}$) from p$_\mathrm{T}=$ 3 GeV/$c$ in the most forward region and up to 50 GeV/$c$. Both prompt and nonprompt (coming from b hadron decays) mesons are observed to be increasingly suppressed with centrality, with a magnitude similar to the one observed at $\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV for the two J/$\psi$ meson components. No dependence on rapidity is observed for either prompt or nonprompt J/$\psi$ mesons. An indication of a lower prompt J/$\psi$ meson suppression at p$_\mathrm{T} >$ 25 GeV/$c$ is seen with respect to that observed at intermediate p$_\mathrm{T}$. The prompt $\psi$(2S) meson yield is found to be more suppressed than that of the prompt J/$\psi$ mesons in the entire p$_\mathrm{T}$ range.
Fraction of J/psi mesons coming from the decay of b hadrons, i.e. nonprompt J/psi meson fraction, as a function of dimuon pT for pp and PbPb collisions, for all centralities.
Fraction of J/psi mesons coming from the decay of b hadrons, i.e. nonprompt J/psi meson fraction, as a function of dimuon rapidity for pp and PbPb collisions, for all centralities.
Differential cross section of prompt J/psi mesons as a function of dimuon pT in pp and PbPb collisions. The PbPb cross sections are normalised by TAA for direct comparison. Global uncertainties arise from the integrated luminosity uncertainty in pp collisions, and the number of minimum bias events and TAA uncertainties for PbPb collisions.
First results on K/$\pi$, p/$\pi$ and K/p fluctuations are obtained with the ALICE detector at the CERN LHC as a function of centrality in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV. The observable $\nu_{\rm dyn}$, which is defined in terms of the moments of particle multiplicity distributions, is used to quantify the magnitude of dynamical fluctuations of relative particle yields and also provides insight into the correlation between particle pairs. This study is based on a novel experimental technique, called the Identity Method, which allows one to measure the moments of multiplicity distributions in case of incomplete particle identification. The results for p/$\pi$ show a change of sign in $\nu_{\rm dyn}$ from positive to negative towards more peripheral collisions. For central collisions, the results follow the smooth trend of the data at lower energies and $\nu_{\rm dyn}$ exhibits a change in sign for p/$\pi$ and K/p.
Beam-energy dependence of nu_dyn.
Beam-energy dependence of nu_dyn.
Beam-energy dependence of nu_dyn.
A search for lepton flavour violating decays of the Higgs boson in the $\mu\tau$ and e$\tau$ decay modes is presented. The search is based on a data set corresponding to an integrated luminosity of 35.9 fb$^{-1}$ of proton-proton collisions collected with the CMS detector in 2016, at a centre-of-mass energy of 13 TeV. No significant excess over the standard model expectation is observed. The observed (expected) upper limits on the lepton flavour violating branching fractions of the Higgs boson are $\mathcal{B}$(H$\to\mu\tau$) < 0.25% (0.25%) and $\mathcal{B}$(H$\to$e$\tau$) < 0.61% (0.37%), at 95% confidence level. These results are used to derive upper limits on the off-diagonal $\mu\tau$ and e$\tau$ Yukawa couplings $\sqrt{|{Y_{\mu\tau}}|^{2}+|{Y_{\tau\mu}}|^{2}} < 1.43 \times 10^{-3}$ and $\sqrt{|{Y_{\mathrm{e}\tau}}|^{2}+|{Y_{\tau\mathrm{e}}}|^{2}} < 2.26 \times 10^{-3}$ at 95% confidence level. The limits on the lepton flavour violating branching fractions of the Higgs boson and on the associated Yukawa couplings are the most stringent to date.
Expected and observed 95 percent CL upper limits on BR(H to mu tau) for each individual category and combined from BDT fit analysis
Expected and observed 95 percent CL upper limits on BR(H to mu tau) for each individual category and combined from collinear mass fit analysis
Expected and observed 95 percent CL upper limits on BR(H to e tau) for each individual category and combined from BDT fit analysis
The inclusive and fiducial $t\bar{t}$ production cross-sections are measured in the lepton+jets channel using 20.2 fb$^{-1}$ of proton-proton collision data at a centre-of-mass energy of 8 TeV recorded with the ATLAS detector at the LHC. Major systematic uncertainties due to the modelling of the jet energy scale and $b$-tagging efficiency are constrained by separating selected events into three disjoint regions. In order to reduce systematic uncertainties in the most important background, the W+jets process is modelled using Z+jets events in a data-driven approach. The inclusive $t\bar{t}$ cross-section is measured with a precision of 5.7% to be $\sigma_{\text{inc}}(t\bar{t})$ = 248.3 $\pm$ 0.7 (stat.) $\pm$ 13.4 (syst.) $\pm$ 4.7 (lumi.) pb, assuming a top-quark mass of 172.5 GeV. The result is in agreement with the Standard Model prediction. The cross-section is also measured in a phase space close to that of the selected data. The fiducial cross-section is $\sigma_{\text{fid}}(t\bar{t})$ = 48.8 $\pm$ 0.1 (stat.) $\pm$ 2.0 (syst.) $\pm$ 0.9 (lumi.) pb with a precision of 4.5%.
The measured inclusive cross section. The first systematic uncertainty (sys_1) is the combined systematic uncertainty excluding luminosity, the second (sys_2) is the luminosity
The measured fiducial cross section. The first systematic uncertainty (sys_1) is the combined systematic uncertainty excluding luminosity, the second (sys_2) is the luminosity
A search for heavy resonances decaying into a pair of $Z$ bosons leading to $\ell^+\ell^-\ell^+\ell^-$ and $\ell^+\ell^-\nu\bar\nu$ final states, where $\ell$ stands for either an electron or a muon, is presented. The search uses proton proton collision data at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 36.1 fb$^{-1}$ collected with the ATLAS detector during 2015 and 2016 at the Large Hadron Collider. Different mass ranges for the hypothetical resonances are considered, depending on the final state and model. The different ranges span between 200 GeV and 2000 GeV. The results are interpreted as upper limits on the production cross section of a spin 0 or spin 2 resonance. The upper limits for the spin 0 resonance are translated to exclusion contours in the context of Type I and Type II two-Higgs-doublet models, while those for the spin 2 resonance are used to constrain the Randall Sundrum model with an extra dimension giving rise to spin 2 graviton excitations.
Distribution of the four-lepton invariant mass (m4l) in the four-lepton search for the ggF-enriched category.
Distribution of the four-lepton invariant mass (m4l) in the four-lepton search for the VBF-enriched category.
Transverse mass mT in the llnunu search for the electron channel.
A search is conducted for new resonances decaying into a $W$ or $Z$ boson and a 125 GeV Higgs boson in the $\nu\bar{\nu}b\bar{b}$, $\ell^{\pm}{\nu}b\bar{b}$, and $\ell^+\ell^-b\bar{b}$ final states, where $\ell ^{\pm}= e^{\pm}$ or $\mu^{\pm}$, in $pp$ collisions at $\sqrt s = 13$ TeV. The data used correspond to a total integrated luminosity of 36.1 fb$^{-1}$ collected with the ATLAS detector at the Large Hadron Collider during the 2015 and 2016 data-taking periods. The search is conducted by examining the reconstructed invariant or transverse mass distributions of $Wh$ and $Zh$ candidates for evidence of a localised excess in the mass range of 220 GeV up to 5 TeV. No significant excess is observed and the results are interpreted in terms of constraints on the production cross-section times branching fraction of heavy $W^\prime$ and $Z^\prime$ resonances in heavy-vector-triplet models and the CP-odd scalar boson $A$ in two-Higgs-doublet models. Upper limits are placed at the 95 % confidence level and range between $9.0\times 10^{-4}$ pb and $8.1\times 10^{-1}$ pb depending on the model and mass of the resonance.
Upper limits on Zprime to Z h production cross section x branching fraction in pb
Upper limits on Wprime to W h production cross section x branching fraction in pb
Upper limits for the scaling factor of the production cross section for V’ times its branching fraction to Wh/Zh in Model A.
A search for resonance-like structures in the $\mathrm{B}^{0}_{\mathrm{s}}\pi^{\pm}$ invariant mass spectrum is performed using proton-proton collision data collected by the CMS experiment at the LHC at $\sqrt{s} = $ 8 TeV, corresponding to an integrated luminosity of 19.7 fb$^{-1}$. The $\mathrm{B}^{0}_{\mathrm{s}}$ mesons are reconstructed in the decay chain $\mathrm{B}^{0}_{\mathrm{s}} \rightarrow \mathrm{J}/\psi\,\phi$, with $\mathrm{J}/\psi \rightarrow \mu^+\mu^-$ and $\phi\rightarrow\mathrm{K^{+}}\mathrm{K^{-}}$. The $\mathrm{B}^{0}_{\mathrm{s}}\pi^{\pm}$ invariant mass distribution shows no statistically significant peaks for different selection requirements on the reconstructed $\mathrm{B}^{0}_{\mathrm{s}}$ and $\pi^{\pm}$ candidates. Upper limits are set on the relative production rates of the X(5568) and $\mathrm{B}^{0}_{\mathrm{s}}$ states times the branching fraction of the decay $\mathrm{X}(5568)^{\pm} \rightarrow \mathrm{B}^{0}_{\mathrm{s}} \pi^{\pm} $. In addition, upper limits are obtained as a function of the mass and the natural width of possible exotic states decaying into $\mathrm{B}^{0}_{\mathrm{s}}\pi^{\pm}$.
Upper limit of the relative production of the X(5568) decaying to $B^s \pi^\pm$, with respect to the inclusive $B^0_s$ production.
The ALICE Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high-transverse momentum trigger hadron in p-Pb collisions at $\sqrt{s_{\rm NN}} =5.02$ TeV. Jets are reconstructed from charged-particle tracks using the anti-$k_{\rm T}$ algorithm with resolution parameter $R=0.2$ and $0.4$. A data-driven statistical approach is used to correct the uncorrelated background jet yield. Recoil jet distributions are reported for jet transverse momentum $15<p_{\rm T,jet}^{\rm ch} <50$ GeV/$c$ and are compared in various intervals of p-Pb event activity, based on charged-particle multiplicity and zero-degree neutral energy in the forward (Pb-going) direction. The semi-inclusive observable is self-normalized and such comparisons do not require the interpretation of p-Pb event activity in terms of collision geometry, in contrast to inclusive jet observables. These measurements provide new constraints on the magnitude of jet quenching in small systems at the LHC. In p-Pb collisions with high event activity, the average medium-induced out-of-cone energy transport for jets with $R=0.4$ and $15<p_{\rm T,jet}^{\rm ch}<50$ GeV/$c$ is measured to be less than 0.4 GeV/$c$ at 90% confidence, which is over an order of magnitude smaller than a similar measurement for central Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV. Comparison is made to theoretical calculations of jet quenching in small systems, and to inclusive jet measurements in p-Pb collisions selected by event activity at the LHC and in d-Au collisions at RHIC.
Corrected Delta_{recoil} distribution of recoil jets with R=0.4 measured for p-Pb collisions at sqrt{s_{NN}} = 5.02 TeV without imposing event activity bias.
Corrected Delta_{recoil} distribution of recoil jets with R=0.4 measured for p-Pb collisions at sqrt{s_{NN}} = 5.02 TeV with event activity ZNA 0-20%.
Corrected Delta_{recoil} distribution of recoil jets with R=0.4 measured for p-Pb collisions at sqrt{s_{NN}} = 5.02 TeV with event activity ZNA 50-100%.
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