Measurement of $Z$ boson production cross-section in $pp$ collisions at $\sqrt{s} = 5.02$ TeV

The LHCb collaboration Aaij, Roel ; Abdelmotteleb, Ahmed Sameh Wagih ; Abellan Beteta, Carlos ; et al.
JHEP 02 (2024) 070, 2024.
Inspire Record 2690798 DOI 10.17182/hepdata.147274

The first measurement of the $Z$ boson production cross-section at centre-of-mass energy $\sqrt{s} = 5.02\,$TeV in the forward region is reported, using $pp$ collision data collected by the LHCb experiment in year 2017, corresponding to an integrated luminosity of $100 \pm 2\,\rm{pb^{-1}}$. The production cross-section is measured for final-state muons in the pseudorapidity range $2.0<\eta<4.5$ with transverse momentum $p_{\rm{T}}> 20\,\rm{GeV/}\it{c}$. The integrated cross-section is determined to be \[ \sigma_{Z \rightarrow \mu^{+}\mu^{-}} = 39.6 \pm 0.7\,(\rm{stat}) \pm 0.6\,(\rm{syst}) \pm 0.8\,(\rm{lumi}) \ \rm{pb} \] for the di-muon invariant mass in the range $60<M_{\mu\mu}<120\,\rm{GeV/}\it{c^{2}}$. This result and the differential cross-section results are in good agreement with theoretical predictions at next-to-next-to-leading order in the strong coupling. Based on a previous LHCb measurement of the $Z$ boson production cross-section in $p$Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV, the nuclear modification factor $R_{p\rm{Pb}}$ is measured for the first time at this energy. The measured values are $1.2^{+0.5}_{-0.3}\,(\rm{stat}) \pm 0.1\,(\rm{syst})$ in the forward region ($1.53<y^*_{\mu}<4.03$) and $3.6^{+1.6}_{-0.9}\,(\rm{stat}) \pm 0.2\,(\rm{syst})$ in the backward region ($-4.97<y^*_{\mu}<-2.47$), where $y^*_{\mu}$ represents the muon rapidity in the centre-of-mass frame.

9 data tables

Measured single differential cross-sections in bins of $y^{Z}$. The first uncertainty is statistical, the second systematic, and the third is from the uncertainty on the integrated luminosity.

Measured single differential cross-sections in bins of $p_{T}^{Z}$. The first uncertainty is statistical, the second systematic, and the third is due to the luminosity.

Measured single differential cross-sections in bins of $\phi_{\eta}^{*}$. The first uncertainty is statistical, the second systematic, and the third is due to the luminosity.

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Evidence for the Higgs boson decay to a $Z$ boson and a photon at the LHC

The ATLAS & CMS collaborations Aad, Georges ; Abbott, Braden Keim ; Abeling, Kira ; et al.
Phys.Rev.Lett. 132 (2024) 021803, 2024.
Inspire Record 2666787 DOI 10.17182/hepdata.142406

The first evidence for the Higgs boson decay to a $Z$ boson and a photon is presented, with a statistical significance of 3.4 standard deviations. The result is derived from a combined analysis of the searches performed by the ATLAS and CMS Collaborations with proton-proton collision data sets collected at the CERN Large Hadron Collider (LHC) from 2015 to 2018. These correspond to integrated luminosities of around 140 fb$^{-1}$ for each experiment, at a center-of-mass energy of 13 TeV. The measured signal yield is $2.2\pm0.7$ times the Standard Model prediction, and agrees with the theoretical expectation within 1.9 standard deviations.

1 data table

The negative profile log-likelihood test statistic, where $\Lambda$ represents the likelihood ratio, as a function of the signal strength $\mu$ derived from the ATLAS data, the CMS data, and the combined result.


Version 2
Measurement of prompt charged-particle production in proton-proton collisions at a centre-of-mass energy of 13 TeV

The LHCb collaboration Aaij, Roel ; Abellán Beteta, Carlos ; Ackernley, Thomas ; et al.
JHEP 01 (2022) 166, 2022.
Inspire Record 1889335 DOI 10.17182/hepdata.136099

The differential cross-section of prompt inclusive production of long-lived charged particles in proton-proton collisions is measured using a data sample recorded by the LHCb experiment at a centre-of-mass energy of ${\sqrt{s} = 13\,\mathrm{TeV}}$. The data sample, collected with an unbiased trigger, corresponds to an integrated luminosity of ${5.4\,\mathrm{nb}^{-1}}$. The differential cross-section is measured as a function of transverse momentum and pseudorapidity in the ranges ${p_\mathrm{T} \in [0.08, 10)\,\mathrm{GeV}\,c^{-1}}$ and ${\eta \in [2.0, 4.8)}$ and is determined separately for positively and negatively charged particles. The results are compared with predictions from various hadronic-interaction models.

6 data tables

Double differential cross-sections of prompt inclusive production of long-lived negatively charged particles as a function of transverse momentum and pseudorapidity.

Double differential cross-sections of prompt inclusive production of long-lived positively charged particles as a function of transverse momentum and pseudorapidity.

Correlation for the uncertainties of the differential cross-section of prompt inclusive production of long-lived charged particles.

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Measurement of antiproton production from antihyperon decays in pHe collisions at $\sqrt{s_{NN}}=110$ GeV

The LHCb collaboration Aaij, R. ; Abdelmotteleb, A.S. W. ; Beteta, C.Abellan ; et al.
Eur.Phys.J.C 83 (2023) 543, 2023.
Inspire Record 2084295 DOI 10.17182/hepdata.130780

The interpretation of cosmic antiproton flux measurements from space-borne experiments is currently limited by the knowledge of the antiproton production cross-section in collisions between primary cosmic rays and the interstellar medium. Using collisions of protons with an energy of 6.5 TeV incident on helium nuclei at rest in the proximity of the interaction region of the LHCb experiment, the ratio of antiprotons originating from antihyperon decays to prompt production is measured for antiproton momenta between 12 and 110 GeV/c. The dominant antihyperon contribution, namely $\bar{\Lambda} \to \bar{p} \pi^+$ decays from promptly produced $\bar{\Lambda}$ particles, is also exclusively measured. The results complement the measurement of prompt antiproton production obtained from the same data sample. At the energy scale of this measurement, the antihyperon contributions to antiproton production are observed to be significantly larger than predictions of commonly used hadronic production models.

2 data tables

Ratio of the antihyperon decays to prompt antiproton production (R_Hbar) in collisions of 6.5 TeV protons on He nuclei at rest in antiproton momentum and transverse momentum intervals. The average momentum and transverse momentum, as predicted by the EPOS-LHC generator for prompt antiprotons, are also listed for each interval. The uncertainty is split into an uncorrelated component, denoted with delta_uncorr, and a component that is fully correlated among the kinematic intervals, denoted delta_corr.

Ratio of the Lbar decays to prompt antiproton production (R_Lbar) in collisions of 6.5 TeV protons on He nuclei at rest in antiproton momentum and transverse momentum intervals. The average momentum and transverse momentum, as predicted by the EPOS-LHC generator for prompt antiprotons, are also listed for each interval. The uncertainty is split into an uncorrelated component, denoted with delta_uncorr, and a component that is fully correlated among the kinematic intervals, denoted delta_corr.


Search for low-mass dilepton resonances in Higgs boson decays to four-lepton final states in proton-proton collisions at $\sqrt{s}$ =13 TeV

The CMS collaboration Tumasyan, A. ; Adam, W. ; Bergauer, T. ; et al.
Eur.Phys.J.C 82 (2022) 290, 2022.
Inspire Record 1961934 DOI 10.17182/hepdata.110659

A search for low-mass dilepton resonances in Higgs boson decays is conducted in the four-lepton final state. The decay is assumed to proceed via a pair of beyond the standard model particles, or one such particle and a Z boson. The search uses proton-proton collision data collected with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 137 fb$^{-1}$, at a center-of-mass energy $\sqrt{s} =$ 13 TeV. No significant deviation from the standard model expectation is observed. Upper limits at 95% confidence level are set on model-independent Higgs boson decay branching fractions. Additionally, limits on dark photon and axion-like particle production, based on two specific models, are reported.

9 data tables

Exclusion limit for BrHXX_Br2Xee

Exclusion limit for BrHXX_Br2Xmumu

Exclusion limit for BrHXX_Br2Xll

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Study of the doubly charmed tetraquark $T_{cc}^+$

The LHCb collaboration Aaij, Roel ; Abdelmotteleb, Ahmed Sameh Wagih ; Abellán Beteta, Carlos ; et al.
Nature Commun. 13 (2022) 3351, 2022.
Inspire Record 1915358 DOI 10.17182/hepdata.113470

An exotic narrow state in the $D^0D^0\pi^+$ mass spectrum just below the $D^{*+}D^0$ mass threshold is studied using a data set corresponding to an integrated luminosity of 9 fb$^{-1}$ acquired with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The state is consistent with the ground isoscalar $T^+_{cc}$ tetraquark with a quark content of $cc\bar{u}\bar{d}$ and spin-parity quantum numbers $\mathrm{J}^{\mathrm{P}}=1^+$. Study of the $DD$ mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell $D^{*+}$ mesons is confirmed by the $D^0\pi^+$ mass distribution. The mass of the resonance and its coupling to the $D^{*}D$ system are analysed. Resonance parameters including the pole position, scattering length, effective range and compositeness are measured to reveal important information about the nature of the $T^+_{cc}$ state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.

20 data tables

Distribution of $D^0 D^0 \pi^+$ mass where the contribution of the non-$D^0$ background has been statistically subtracted. Uncertainties on the data points are statistical only and represent one standard deviation, calculated as a sum in quadrature of the assigned weights from the background-subtraction procedure.

Mass distribution for $D^0 \pi^+$ pairs from selected $D^0 D^0 \pi^+$ candidates with a mass below the $D^{*+}D^0$ mass threshold with non-$D^0$ background subtracted. Uncertainties on the data points are statistical only and represent one standard deviation, calculated as a sum in quadrature of the assigned weights from the background-subtraction procedure.

$D^0 D^0$~mass distributions for selected candidates with the $D^0$ background subtracted. Uncertainties on the data points are statistical only and represent one standard deviation, calculated as a sum in quadrature of the assigned weights from the background-subtraction procedure.

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Observation of an exotic narrow doubly charmed tetraquark

The LHCb collaboration Aaij, Roel ; Abdelmotteleb, Ahmed Sameh Wagih ; Abellán Beteta, Carlos ; et al.
Nature Phys. 18 (2022) 751-754, 2022.
Inspire Record 1915457 DOI 10.17182/hepdata.114869

Conventional hadronic matter consists of baryons and mesons made of three quarks and quark-antiquark pairs, respectively. The observation of a new type of hadronic state, a doubly charmed tetraquark containing two charm quarks, an anti-$u$ and an anti-$d$ quark, is reported using data collected by the LHCb experiment at the Large Hadron Collider. This exotic state with a mass of about 3875 MeV$/c^2$ manifests itself as a narrow peak in the mass spectrum of $D^0D^0\pi^+$ mesons just below the $D^{*+}D^0$ mass threshold. The near threshold mass together with a strikingly narrow width reveals the resonance nature of the state.

2 data tables

Distribution of $D^0 D^0 \pi^+$ mass where the contribution of the non-$D^0$ background has been statistically subtracted. Uncertainties on the data points are statistical only and represent one standard deviation, calculated as a sum in quadrature of the assigned weights from the background-subtraction procedure.

Distribution of $D^0 D^0 \pi^+$ mass where the contribution of the non-$D^0$ background has been statistically subtracted by assigning the a weight to every candidate.


Test of lepton universality in beauty-quark decays

The LHCb collaboration Aaij, Roel ; Abellán Beteta, Carlos ; Ackernley, Thomas ; et al.
Nature Phys. 18 (2022) 277-282, 2022.
Inspire Record 1852846 DOI 10.17182/hepdata.106855

The Standard Model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Previous measurements have shown a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton-proton collision data collected with the LHCb detector at CERN's Large Hadron Collider. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the Standard Model, such as a new fundamental interaction between quarks and leptons.

1 data table

Likelihood function from the fit to the nonresonant $B^+$ --> $K^+\ell^+ \ell^−$ candidates profiled as a function of $R_K$.


Version 3
Search for long-lived particles decaying to jets with displaced vertices in proton-proton collisions at $\sqrt{s}=$ 13 TeV

The CMS collaboration Sirunyan, A.M. ; Tumasyan, A. ; Adam, W. ; et al.
Phys.Rev.D 104 (2021) 052011, 2021.
Inspire Record 1861146 DOI 10.17182/hepdata.102798

A search is presented for long-lived particles produced in pairs in proton-proton collisions at the LHC operating at a center-of-mass energy of 13 TeV. The data were collected with the CMS detector during the period from 2015 through 2018, and correspond to a total integrated luminosity of 140 fb$^{-1}$. This search targets pairs of long-lived particles with mean proper decay lengths between 0.1 and 100 mm, each of which decays into at least two quarks that hadronize to jets, resulting in a final state with two displaced vertices. No significant excess of events with two displaced vertices is observed. In the context of $R$-parity violating supersymmetry models, the pair production of long-lived neutralinos, gluinos, and top squarks is excluded at 95% confidence level for cross sections larger than 0.08 fb, masses between 800 and 3000 GeV, and mean proper decay lengths between 1 and 25 mm.

32 data tables

Event yields in the control samples in data. The ''one-vertex'' events correspond to events containing exactly one vertex with the specified number of tracks. The ''two-vertex'' events have two or more vertices containing the specified numbers of tracks. We seek the signal in the $\geq$5-track two-vertex sample.

The distribution of distances between vertices in the $x$-$y$ plane, $d_{\mathrm{VV}}$, for three simulated multijet signals each with a mass of 1600 GeV, with the background template distribution overlaid. The production cross section for each signal model is assumed to be the lower limit excluded by CMS-EXO-17-018, corresponding to values of 0.8, 0.25, and 0.15 fb for the samples with $c\tau =$ 0.3, 1.0, and 10 mm, respectively. The last bin includes the overflow events. The two vertical pink dashed lines separate the regions used in the fit.

Multijet signal efficiencies as a function of the signal mass and lifetime for events satisfying all event and vertex requirements, with corrections based on systematic differences in the vertex reconstruction efficiency between data and simulation.

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Precise determination of the B0s-B0sbar oscillation frequency

The LHCb collaboration Aaij, R. ; Beteta, C. Abellán ; Ackernley, T. ; et al.
Nature Phys. 18 (2022) 1-5, 2022.
Inspire Record 1857623 DOI 10.17182/hepdata.105881

Mesons comprising a beauty quark and a strange quark can oscillate between particle (B0s) and antiparticle (B0s) flavour eigenstates, with a frequency given by the mass difference between heavy and light mass eigenstates, deltams. Here we present ameasurement of deltams using B0s2DsPi decays produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The oscillation frequency is found to be deltams = 17.7683 +- 0.0051 +- 0.0032 ps-1, where the first uncertainty is statistical and the second systematic. This measurement improves upon the current deltams precision by a factor of two. We combine this result with previous LHCb measurements to determine deltams = 17.7656 +- 0.0057 ps-1, which is the legacy measurement of the original LHCb detector.

1 data table

Summary of LHCb measurements. Comparison of LHCb $\Delta m_s$ measurements from Refs. [8–11], the result presented in this article and their average. For the average, following systematic uncertainties are assumed to be fully correlated(:) zScale, MomentumScale, VeloAlignment and DecayTimeBias. The measurements are statistically uncorrelated.