A new algorithm is presented to discriminate reconstructed hadronic decays of tau leptons ($\tau_\mathrm{h}$) that originate from genuine tau leptons in the CMS detector against $\tau_\mathrm{h}$ candidates that originate from quark or gluon jets, electrons, or muons. The algorithm inputs information from all reconstructed particles in the vicinity of a $\tau_\mathrm{h}$ candidate and employs a deep neural network with convolutional layers to efficiently process the inputs. This algorithm leads to a significantly improved performance compared with the previously used one. For example, the efficiency for a genuine $\tau_\mathrm{h}$ to pass the discriminator against jets increases by 10-30% for a given efficiency for quark and gluon jets. Furthermore, a more efficient $\tau_\mathrm{h}$ reconstruction is introduced that incorporates additional hadronic decay modes. The superior performance of the new algorithm to discriminate against jets, electrons, and muons and the improved $\tau_\mathrm{h}$ reconstruction method are validated with LHC proton-proton collision data at $\sqrt{s} =$ 13 TeV.
Decay mode confusion matrix. For a given generated decay mode, the fractions of reconstructed tau_h in different decay modes are given, as well as the fraction of generated tau_h that are not reconstructed. Both the generated and reconstructed tau_h need to fulfil pt > 20 GeV and |eta| < 2.3. The tau_h candidates come from a Z to tau tau event sample with m(tau, tau) > 50 GeV.
Efficiency for quark and gluon jets to pass different tau identification discriminators versus the efficiency for genuine tau_h. The upper two plots are obtained with jets from the W+jets simulated sample and the lower two plots with jets from the tt sample. The left two plots include jets and genuine tau_h with pt < 100 GeV, whereas the right two plots include those with pt > 100 GeV. The working points are indicated as full circles. The efficiency for jets from the W+jets event sample, enriched in quark jets, to pass the discriminators is higher compared to jets from the tt event sample, which has a larger fraction of gluon and b-quark jets. The jet efficiency for a given tau_h efficiency is larger for jets and tau_h with pt < 100 GeV than for those with pt > 100 GeV. Compared with the previously used MVA discriminator, the DEEPTAU discriminator reduces the jet efficiency for a given tau_h efficiency by consistently more than a factor of 1.8, and by more at high tau_h efficiency. The additional gain at high pt comes from the inclusion of updated decay modes in the tau_h reconstruction, as illustrated by the curves for the previously used MVA discriminator but including reconstructed tau_h candidates with additional decay modes.
Efficiency for quark and gluon jets to pass different tau identification discriminators versus the efficiency for genuine tau_h. The upper two plots are obtained with jets from the W+jets simulated sample and the lower two plots with jets from the tt sample. The left two plots include jets and genuine tau_h with pt < 100 GeV, whereas the right two plots include those with pt > 100 GeV. The working points are indicated as full circles. The efficiency for jets from the W+jets event sample, enriched in quark jets, to pass the discriminators is higher compared to jets from the tt event sample, which has a larger fraction of gluon and b-quark jets. The jet efficiency for a given tau_h efficiency is larger for jets and tau_h with pt < 100 GeV than for those with pt > 100 GeV. Compared with the previously used MVA discriminator, the DEEPTAU discriminator reduces the jet efficiency for a given tau_h efficiency by consistently more than a factor of 1.8, and by more at high tau_h efficiency. The additional gain at high pt comes from the inclusion of updated decay modes in the tau_h reconstruction, as illustrated by the curves for the previously used MVA discriminator but including reconstructed tau_h candidates with additional decay modes.
The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/$c$ in p-Pb collisions and the resolution at high transverse momentum improves by about 40% when including the TRD information in track reconstruction. The triggering capability is demonstrated both for jet, light nuclei, and electron selection.
Most probable charge deposit signal normalised to that of minimum ionising particles as a function of $\beta\gamma$ for $\pi$, $\it{e}$ test beam (dE/dx). Statistical uncertainties as vertical error bars.
Most probable charge deposit signal normalised to that of minimum ionising particles as a function of $\beta\gamma$ for $\pi$, $\it{e}$ test beam (dE/dx + TR). Statistical uncertainties as vertical error bars.
Most probable charge deposit signal normalised to that of minimum ionising particles as a function of $\beta\gamma$ for $\pi$, $\it{e}$ and proton in pp collisions ($\sqrt{s} = 7$ TeV). Statistical uncertainties as vertical error bars. Uncertainties in momentum and thus $\beta \gamma$ determination are drawn as horizontal error bars.
The measurement of primary $\pi^{\pm}$, K$^{\pm}$, p and $\overline{p}$ production at mid-rapidity ($|y| <$ 0.5) in proton-proton collisions at $\sqrt{s} = 7$ TeV performed with ALICE (A Large Ion Collider Experiment) at the Large Hadron Collider (LHC) is reported. Particle identification is performed using the specific ionization energy loss and time-of-flight information, the ring-imaging Cherenkov technique and the kink-topology identification of weak decays of charged kaons. Transverse momentum spectra are measured from 0.1 up to 3 GeV/$c$ for pions, from 0.2 up to 6 GeV/$c$ for kaons and from 0.3 up to 6 GeV/$c$ for protons. The measured spectra and particle ratios are compared with QCD-inspired models, tuned to reproduce also the earlier measurements performed at the LHC. Furthermore, the integrated particle yields and ratios as well as the average transverse momenta are compared with results at lower collision energies.
Combined transverse momentum spectra of PI, K and P, sum of particles and antiparticles, measured at mid-rapidity in pp collisions at SQRT(S) = 7 TeV normalized to the number of inelastic collisions. Statistical and systematic uncertainties are reported. The uncertainty due to the normalization to inelastic collisions (+7-4 %) is not included.
Kaon/Pion ratio in pp collisions at SQRT(S) = 7 TeV.
Proton/Pion ratio in pp collisions at SQRT(S) = 7 TeV.