Date

Collaboration

Phrases

Reactions

Cmenergies

Evidence for associated production of a Higgs boson with a top quark pair in final states with electrons, muons, and hadronically decaying $\tau$ leptons at $\sqrt{s} =$ 13 TeV

The CMS collaboration Sirunyan, Albert M ; Tumasyan, Armen ; Adam, Wolfgang ; et al.
JHEP 1808 (2018) 066, 2018.
Inspire Record 1662661 DOI 10.17182/hepdata.84635

Results of a search for the standard model Higgs boson produced in association with a top quark pair ($\mathrm{t\overline{t}}$H) in final states with electrons, muons, and hadronically decaying $\tau$ leptons are presented. The analyzed data set corresponds to an integrated luminosity of 35.9 fb$^{-1}$ recorded in proton-proton collisions at $\sqrt{s} =$ 13 TeV by the CMS experiment in 2016. The sensitivity of the search is improved by using matrix element and machine learning methods to separate the signal from backgrounds. The measured signal rate amounts to 1.23 $^{+0.45}_{-0.43}$ times the production rate expected in the standard model, with an observed (expected) significance of 3.2$\sigma$ (2.8$\sigma$), which represents evidence for $\mathrm{t\overline{t}}$H production in those final states. An upper limit on the signal rate of 2.1 times the standard model production rate is set at 95% confidence level.

1 data table

Signal rates $\mu$, in units of the SM $\mathrm{t\overline(t}H}$ production rate, measured in each of the categories individually and for the combination of all six categories. The blue (green) band corresponds to the statistical (total) uncertainty on the combined signal rate.


Measurements of low-$p_{\rm T}$ electrons from semileptonic heavy-flavour hadron decays at mid-rapidity in pp and Pb-Pb collisions at $\mathbf{\sqrt{{\it s}_\mathrm{NN}}}$ = 2.76 TeV

The ALICE collaboration Acharya, Shreyasi ; Torales - Acosta, Fernando ; Adamova, Dagmar ; et al.
No Journal Information, 2018.
Inspire Record 1672811 DOI 10.17182/hepdata.85021

Transverse-momentum ($p_{\rm T}$) differential yields of electrons from semileptonic heavy-flavour hadron decays have been measured in the most central (0-10%) and in semi-central (20-40%) Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV. The corresponding production cross section in pp collisions has been measured at the same energy with substantially reduced systematic uncertainties with respect to previously published results. The modification of the yield in Pb-Pb collisions with respect to the expectation from an incoherent superposition of nucleon-nucleon collisions is quantified at mid-rapidity ($|y|$ $<$ 0.8) in the $p_{\rm T}$ interval 0.5-3 GeV/$c$ via the nuclear modification factor, $R_{\rm AA}$. This paper extends the $p_{\rm T}$ reach of the $R_{\rm AA}$ measurement towards significantly lower values with respect to a previous publication. In Pb-Pb collisions the $p_{\rm T}$-differential measurements of yields at low $p_{\rm T}$ are essential to investigate the scaling of heavy-flavour production with the number of binary nucleon-nucleon collisions. Heavy-quark hadronization, a collective expansion and even initial-state effects, such as the nuclear modification of the Parton Distribution Functions, are also expected to have a significant effect on the measured distribution.

5 data tables

Cross section of electron from heavy-flavour hadron decays in pp collisions at 2.76 TeV; additional systematic uncertainty: ± 1.9% (normalization/luminosity uncertainty) not shown.

Spectra of electron from heavy-flavour hadron decays in 0-10% centrality class.

Spectra of electron from heavy-flavour hadron decays in 20-40% centrality class.

More…

Search for disappearing tracks as a signature of new long-lived particles in proton-proton collisions at $\sqrt{s} =$ 13 TeV

The CMS collaboration Sirunyan, Albert M ; Tumasyan, Armen ; Adam, Wolfgang ; et al.
JHEP 1808 (2018) 016, 2018.
Inspire Record 1669245 DOI 10.17182/hepdata.84707

A search is presented for long-lived charged particles that decay within the CMS detector and produce the signature of a disappearing track. A disappearing track is an isolated track with missing hits in the outer layers of the silicon tracker, little or no energy in associated calorimeter deposits, and no associated hits in the muon detectors. This search uses data collected with the CMS detector in 2015 and 2016 from proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC, corresponding to an integrated luminosity of 38.4 fb$^{−1}$. The results of the search are interpreted in the context of the anomaly-mediated supersymmetry breaking model. The data are consistent with the background-only hypothesis. Limits are set on the product of the cross section for direct production of charginos and their branching fraction to a neutralino and a pion, as a function of the chargino mass and lifetime. At 95% confidence level, charginos with masses below 715 (695) GeV are excluded for a lifetime of 3 (7) ns, as are charginos with lifetimes from 0.5 to 60 ns for a mass of 505 GeV. These are the most stringent limits using a disappearing track signature on this signal model for chargino lifetimes above ≈0.7 ns.

14 data tables

Predicted signal yields for the 2015 data-taking period, corresponding to $2.7\,\text{fb}^{-1}$, after the application of each of the disappearing track selections for three chargino lifetime hypotheses ($\tau = 0.3$, $3.3$, and $33\,\text{ns}{}$) with a chargino mass of $700\,\text{GeV}{}$. The selections listed are cumulative, i.e., only the events and objects passing a given selection are considered in subsequent selections. The uncertainties shown include only the statistical uncertainty resulting from the limited sizes of the generated samples.

Signal acceptance for each of the generated chargino masses and lifetimes for $\mathrm{p}\mathrm{p} \rightarrow \widetilde{\chi}^\pm_{1} \widetilde{\chi}^\mp_{1}$ events. The denominator for the acceptance is the total number of $\widetilde{\chi}^\pm_{1} \widetilde{\chi}^\mp_{1}$ events generated, with no generator-level filtering, while the numerator is the number of those events that are selected by the disappearing track signal selection, after being processed with the same reconstruction software used on the data. The acceptance corresponds to the 2015 data-taking period. The uncertainties are only the statistical uncertainties resulting from the sizes of the generated samples.

Signal acceptance for each of the generated chargino masses and lifetimes for $\mathrm{p}\mathrm{p} \rightarrow \widetilde{\chi}^\pm_{1} \widetilde{\chi}^\mp_{1}$ events. The denominator for the acceptance is the total number of $\widetilde{\chi}^\pm_{1} \widetilde{\chi}^\mp_{1}$ events generated, with no generator-level filtering, while the numerator is the number of those events that are selected by the disappearing track signal selection, after being processed with the same reconstruction software used on the data. The acceptance corresponds to the 2016A data-taking period. The uncertainties are only the statistical uncertainties resulting from the sizes of the generated samples.

More…

Version 3
Measurement of $b$-hadron pair production with the ATLAS detector in proton-proton collisions at $\sqrt{s}=8$ TeV

The ATLAS collaboration Aaboud, M. ; Aad, Georges ; Abbott, Brad ; et al.
JHEP 1711 (2017) 062, 2017.
Inspire Record 1598613 DOI 10.17182/hepdata.80234

A measurement of b-hadron pair production is presented, based on a data set corresponding to an integrated luminosity of 11.4 fb$^{−1}$ of proton-proton collisions recorded at $ \sqrt{s}=8 $ TeV with the ATLAS detector at the LHC. Events are selected in which a b-hadron is reconstructed in a decay channel containing J/ψ → μμ, and a second b-hadron is reconstructed in a decay channel containing a muon. Results are presented in a fiducial volume defined by kinematic requirements on three muons based on those used in the analysis. The fiducial cross section is measured to be 17.7 ± 0.1(stat.) ± 2.0(syst.) nb. A number of normalised differential cross sections are also measured, and compared to predictions from the Pythia8, Herwig++, MadGraph5_aMC@NLO+Pythia8 and Sherpa event generators, providing new constraints on heavy flavour production.

30 data tables

Normalised differential cross sections and corresponding uncertainties in bins of $\Delta R(J/\psi,\mu)$.

$B_{c}$ and $B + D$ corrections removed from the fitted data for $\Delta R(J/\psi,\mu)$.

Normalised differential cross sections and corresponding uncertainties in bins of $\Delta R(J/\psi,\mu) (p_{T} \ge 20 { GeV})$.

More…

Version 5
Search for squarks and gluinos in final states with jets and missing transverse momentum using 36  fb$^{-1}$ of $\sqrt{s}=13$  TeV pp collision data with the ATLAS detector

The ATLAS collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
Phys.Rev. D97 (2018) 112001, 2018.
Inspire Record 1641270 DOI 10.17182/hepdata.77891

A search for the supersymmetric partners of quarks and gluons (squarks and gluinos) in final states containing hadronic jets and missing transverse momentum, but no electrons or muons, is presented. The data used in this search were recorded in 2015 and 2016 by the ATLAS experiment in s=13  TeV proton-proton collisions at the Large Hadron Collider, corresponding to an integrated luminosity of 36.1  fb-1. The results are interpreted in the context of various models where squarks and gluinos are pair produced and the neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 2.03 TeV for a simplified model incorporating only a gluino and the lightest neutralino, assuming the lightest neutralino is massless. For a simplified model involving the strong production of mass-degenerate first- and second-generation squarks, squark masses below 1.55 TeV are excluded if the lightest neutralino is massless. These limits substantially extend the region of supersymmetric parameter space previously excluded by searches with the ATLAS detector.

426 data tables

Observed and expected background and signal effective mass distributions for SR2j-2100. For signal, a squark direct decay model where squarks have mass of 600 GeV and the neutralino1 has mass of 595 GeV is shown.

Observed 95% CL upper limit on the signal cross-section from searches in a SUSY scenario where squarks are produced in pairs and decay directly into the lightest neutralino, $\tilde{q} \rightarrow q \tilde{\chi}_{1}^{0}$.

Expected 95% CL exclusion contours from searches on the light-flavor squark and lightest neutralino masses in a SUSY scenario where squarks are produced in pairs and decay directly into the lightest neutralino, $\tilde{q} \rightarrow q \tilde{\chi}_{1}^{0}$.