This paper presents a search for a Higgs boson produced in association with a charm quark (cH) which allows to probe the Higgs-charm Yukawa coupling strength modifier $κ_\mathrm{c}$. Higgs boson decays to a pair of W bosons are considered, where one W boson decays to an electron and a neutrino, and the other \PW boson decays to a muon and a neutrino. The data, corresponding to an integrated luminosity of 138 fb$^{-1}$, were collected between 2016 and 2018 with the CMS detector at the LHC at a center-of-mass energy of $\sqrt{s}$ = 13 TeV. Upper limits at the 95% confidence level (CL) are set on the ratio of the measured yield to the standard model expectation for cH production. The observed (expected) upper limit is 1065 (506). When combined with the previous search for cH in the diphoton decay channel of the Higgs boson, the limits are interpreted as observed (expected) constraints at 95% CL on the value of $κ_\mathrm{c}$, $\lvertκ_\mathrm{c}\rvert$ $\lt$ 47 (51).
Upper limits of $\mu_{cH}$ at 95%CL for each data-taking period.
Two-dimensional likelihood contour of $\mu_{bkg-H+c}$ and $\mu_{cH}$.
Upper limits of $\mu_{cH}$ at 95% CL of the combined analysis
The first measurement at midrapidity ($|y| < 0.5$) of the production yield of the strange-charm baryons $Ξ_c^+$ and $Ξ_c^0$ as a function of charged-particle multiplicity in proton-proton collisions at $\sqrt{s} = 13$ TeV with the ALICE experiment at the LHC is reported. The $Ξ_c^+$ baryon is reconstructed via the $Ξ_c^+ \rightarrow Ξ^-π^+π^+$ decay channel in the range $4 < p_{\rm T} < 12$ GeV/$c$, while the $Ξ_c^0$ baryon is reconstructed via both the $Ξ_c^0 \rightarrow Ξ^-π^+$ and $Ξ_c^0 \rightarrow Ξ^-e^+ν_e$ decay channels in the range $2 < p_{\rm T} < 12$ GeV/$c$. The baryon-to-meson ($Ξ_c^{0,+}/D^0$) and the baryon-to-baryon ($Ξ_c^{0,+}/Λ_c^+$) production yield ratios show no significant dependence on multiplicity. In addition, the observed yield ratios are not described by theoretical predictions that model charm-quark fragmentation based on measurements at $e^+e^-$ and $e^-$p colliders, indicating differences in the charm-baryon production mechanism in pp collisions. A comparison with different event generators and tunings, including different modelling of the hadronisation process, is also discussed. Moreover, the branching-fraction ratio of BR($Ξ_c^0 \rightarrow Ξ^-e^+ν_e$)/BR($Ξ_c^0 \rightarrow Ξ^-π^+$) is measured as 0.825 $\pm$ 0.094 (stat.) $\pm$ 0.081 (syst.). This value supersedes the previous ALICE measurement, improving the statistical precision by a factor of 1.6.
$p_{\rm T}$-differential per-event yield of prompt $\Xi_c^0$ baryons measured in the different multiplicity classes.
$p_{\rm T}$-differential per-event yield of prompt $\Xi_c^+$ baryons measured in the different multiplicity classes.
Ratio between the prompt $\Xi_c^0$ baryons in a multiplicity class to the multiplicity-integrated (INEL $>$ 0) class.
We present the first measurements of the forward and midrapidity $η$-meson cross sections from $p$$+$$p$ collisions at $\sqrt{s}=500$ and $510$~GeV, respectively. We also report the midrapidity $η/π^0$ ratio at 510 GeV. The forward cross section is measured differentially in $η$-meson transverse momentum ($p_T$) from 1.0 to 6.5~GeV/$c$ for pseudorapidity $3.0<|η|<3.8$. The midrapidity cross section is measured from 3.5 to 44 GeV/$c$ for pseudorapidity $|η|<0.35$. Both cross sections serve as critical inputs to an updated global analysis of the $η$-meson fragmentation functions.
The invariant differential cross section of $\eta$ mesons at forward rapidity in pp collisions at center-of-mass energy 500 GeV.
The invariant differential cross section of $\eta$ mesons at central rapidity in pp collisions at center-of-mass energy 510 GeV.
The ratio of $\eta$ to $\pi^0$ cross sections at central rapidity in pp collisions at center-of-mass energy 510 GeV.
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured low-mass vector-meson ($ω+ρ$ and $ϕ$) production through the dimuon decay channel at forward rapidity $(1.2<|\mbox{y}|<2.2)$ in $p$$+$$p$ and Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$~GeV. The low-mass vector-meson yield and nuclear-modification factor were measured as a function of the average number of participating nucleons, $\langle N_{\rm part}\rangle$, and the transverse momentum $p_T$. These results were compared with those obtained via the kaon decay channel in a similar $p_T$ range at midrapidity. The nuclear-modification factors in both rapidity regions are consistent within the uncertainties. A comparison of the $ω+ρ$ and $J/ψ$ mesons reveals that the light and heavy flavors are consistently suppressed across both $p_T$ and ${\langle}N_{\rm part}\rangle$. In contrast, the $ϕ$ meson displays a nuclear-modification factor consistent with unity, suggesting strangeness enhancement in the medium formed.
The differential cross sections of $\omega+\rho$ mesons as a function of $p_T$ in $p+p$ collisions. The systematic uncertainties of type-A (uncorrelated) are combined with statistical uncertainties in quadrature and are labeled as stat. Type-B (correlated) systematic uncertainties are listed as sys.
The differential cross sections of $\phi$ meson as a function of $p_T$ in $p+p$ collisions. The systematic uncertainties of type-A (uncorrelated) are combined with statistical uncertainties in quadrature and are labeled as stat. Type-B (correlated) systematic uncertainties are listed as sys.
The invariant yields of $\phi$ and $\omega+\rho$ mesons as a function of $p_T$ in Au+Au collisions. The systematic uncertainties of type-A (uncorrelated) are combined with statistical uncertainties in quadrature and are labeled as stat. Type-B (correlated) systematic uncertainties are listed as sys.
The jet cross-section and jet-substructure observables in $p$$+$$p$ collisions at $\sqrt{s}=200$ GeV were measured by the PHENIX Collaboration at the Relativistic Heavy Ion Collider (RHIC). Jets are reconstructed from charged-particle tracks and electromagnetic-calorimeter clusters using the anti-$k_{t}$ algorithm with a jet radius $R=0.3$ for jets with transverse momentum within $8.0<p_T<40.0$ GeV/$c$ and pseudorapidity $|η|<0.15$. Measurements include the jet cross section, as well as distributions of SoftDrop-groomed momentum fraction ($z_g$), charged-particle transverse momentum with respect to jet axis ($j_T$), and radial distributions of charged particles within jets ($r$). Also meaureed was the distribution of $ξ=-ln(z)$, where $z$ is the fraction of the jet momentum carried by the charged particle. The measurements are compared to theoretical next-to and next-to-next-to-leading-order calculatios, PYTHIA event generator, and to other existing experimental results. Indicated from these meaurements is a lower particle multiplicity in jets at RHIC energies when compared to models. Also noted are implications for future jet measurements with sPHENIX at RHIC as well as at the future Electron-Ion Collider.
The jet differential cross section as a function of jet $p_T$. Statistical uncertainties are typically smaller than the data points while systematic uncertainties are shown with boxes. An overall normalization systematic of 7% is not included in the point-by-point systematic uncertainties.
Distribution of the SoftDrop groomed momentum fraction $z_g$ for different jet $p_T$ bins. Standard SoftDrop parameters were used ($z_{cut}<0.1$ and $\beta=0$).
$\xi$ distributions for different jet $p_T$ bins.
Ultrarelativistic heavy-ion collisions create a quark-gluon plasma (QGP), a hot and dense state of strongly interacting QCD matter. In ultracentral collisions, the QGP volume remains nearly constant event-by-event, while its total entropy can fluctuate due to quantum effects, leading to temperature variations. These features allow the correlation between the mean transverse momentum $(\langle p_{\mathrm{T}} \rangle)$ of charged hadrons and their multiplicity to serve as a probe of the QGP's speed of sound, $c_{s}$. This study extracts $c_{s}$ by analyzing the relative increase in $\langle p_{\mathrm{T}} \rangle$ with respect to the charged-particle density $(\langle \mathrm{d}N_\mathrm{ch}/\mathrm{d}\eta \rangle)$ at midrapidity in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02~\mathrm{TeV}$, using data from the ALICE detector. Centrality is determined with estimators based on multiplicity and transverse energy, applying a pseudorapidity gap to reduce selection biases. The extracted value of $c_{s}^{2}$ is found to strongly depend on the employed centrality estimator and ranges between $0.1146 \pm 0.0028 \,\mathrm{(stat.)} \pm 0.0065 \,\mathrm{(syst.)}$ and $0.4374 \pm 0.0006 \mathrm{(stat.)} \pm 0.0184 \mathrm{(syst.)}$ in natural units. Additionally, the event-by-event $[p_{\mathrm{T}}]$ distribution is studied through its variance, skewness, and kurtosis. A pronounced decrease in the self-normalized variance and a peak followed by a drop in skewness suggest the suppression of impact-parameter fluctuations in ultracentral collisions. These observations provide new insights into the thermodynamic properties and initial-state fluctuations of the QGP.
Average number of participating nucleons ($\langle N_{\mathrm{part}} \rangle$) as a function of centrality percentile in $\mathrm{Pb}-\mathrm{Pb}$ collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02~\mathrm{TeV}$. Data points are shown for centrality estimators based on $N_{\mathrm{ch}}$, ${N_{\mathrm{tracklets}}}$, and $E_{\mathrm{T}}$ within $|\eta|\leq 0.8$.
Average number of participating nucleons ($\langle N_{\mathrm{part}} \rangle$) as a function of centrality percentile in $\mathrm{Pb}-\mathrm{Pb}$ collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02~\mathrm{TeV}$. Data points are shown for centrality estimator based on $N_{\mathrm{ch}} \in$ $-3.7<\eta<-1.7$ and $2.8 < \eta <5.1$.
Normalized $p_{\mathrm{T}}$-spectrum ratio as a function as a function of centrality in $\mathrm{Pb}-\mathrm{Pb}$ collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02~\mathrm{TeV}$. Data points are shown for centrality estimator based on $N_{\mathrm{ch}} \in$ $0.5 \leq |\eta|\leq 0.8$.
While dual-phase xenon time projection chambers (TPCs) have driven the sensitivity towards weakly interacting massive particles (WIMPs) at the GeV/c^2 to TeV/c^2 mass scale, the scope for sub-GeV/c^2 dark matter particles is hindered by a limited nuclear recoil energy detection threshold. One approach to probe for lighter candidates is to consider cases where they have been boosted by collisions with cosmic rays in the Milky Way, such that the additional kinetic energy lifts their induced signatures above the nominal threshold. In this Letter, we report first results of a search for cosmic ray-boosted dark matter (CRDM) with a combined 4.2 tonne-year exposure from the LUX-ZEPLIN (LZ) experiment. We observe no excess above the expected backgrounds and establish world-leading constraints on the spin-independent CRDM-nucleon cross section as small as 3.9 * 10^{-33} cm^2 at 90% confidence level for sub-GeV/c^2 masses.
90% CL CRDM-nucleon cross sections
A search for the violation of the charge-parity ($CP$) symmetry in the production of top quarks in association with Z bosons is presented, using events with at least three charged leptons and additional jets. The search is performed in a sample of proton-proton collision data collected by the CMS experiment at the CERN LHC in 2016-2018 at a center-of-mass energy of 13 TeV and in 2022 at 13.6 TeV, corresponding to a total integrated luminosity of 173 fb$^{-1}$. For the first time in this final state, observables that are odd under the $CP$ transformation are employed. Also for the first time, physics-informed machine-learning techniques are used to construct these observables. While for standard model (SM) processes the distributions of these observables are predicted to be symmetric around zero, $CP$-violating modifications of the SM would introduce asymmetries. Two $CP$-odd operators $\mathcal{O}_\text{tW}^\text{I}$ and $\mathcal{O}_\text{tZ}^\text{I}$ in the SM effective field theory are considered that may modify the interactions between top quarks and electroweak bosons. The obtained results are consistent with the SM prediction within two standard deviations, and exclusion limits on the associated Wilson coefficients of $-$2.7 $\lt$$c_\text{tW}^\text{I}$$\lt$ 2.5 and $-$0.2 $\lt$$c_\text{tZ}^\text{I}$$\lt$ 2.0 are set at 95% confidence level. The largest discrepancy is observed in $c_\text{tZ}^\text{I}$ where data is consistent with positive values, with an observed local significance with respect to the SM hypothesis of 2.5 standard deviations, when only linear terms are considered.
Distribution of the discretized $c_{\mathrm{tW}}^{\mathrm{I}}$ score for events in the $c_{\mathrm{tW}}^{\mathrm{I}}$-like category in tZq events. The contributions from the SM, linear, and quadratic terms when $c_{\mathrm{tW}}^{\mathrm{I}}$ is set to unity are plotted separately.
Distribution of the discretized $c_{\mathrm{tZ}}^{\mathrm{I}}$ score for events in the $c_{\mathrm{tZ}}^{\mathrm{I}}$-like category in $t\bar{t}Z$ events. The contributions from the SM, linear, and quadratic terms when $c_{\mathrm{tZ}}^{\mathrm{I}}$ is set to unity are plotted separately.
Distribution of the discretized $c_{\mathrm{tW}}^{\mathrm{I}}$ score for events in the $c_{\mathrm{tW}}^{\mathrm{I}}$-like category, compared with the predictions obtained when all fit parameters are set to their maximum likelihood value in the linear fit.
A measurement of event-shape variables is presented, using a data sample produced in a special run with approximately one inelastic proton-proton collision per bunch crossing. The data were collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 64 $\mu$b$^{-1}$. A number of observables related to the overall distribution of charged particles in the collisions are corrected for detector effects and compared with simulations. Inclusive event-shape distributions, as well as differential distributions of event shapes as functions of charged-particle multiplicity, are studied. None of the models investigated is able to satisfactorily describe the data. Moreover, there are significant features common amongst all generator setups studied, particularly showing data being more isotropic than any of the simulations. Multidimensional unfolded distributions are provided, along with their correlations.
The unfolded charged particle multiplicity distribution of inelastic proton-proton collisions with at least three charged particles with transverse momentum higher than 0.5 GeV and pseudorapidity between -2.4 and 2.4. The total area of the histogram is normalised to 1.
The unfolded charged particle invariant mass distribution of inelastic proton-proton collisions with at least three charged particles with transverse momentum higher than 0.5 GeV and pseudorapidity between -2.4 and 2.4. The total area of the histogram is normalised to 1.
The unfolded charged particle sphericity distribution of inelastic proton-proton collisions with at least three charged particles with transverse momentum higher than 0.5 GeV and pseudorapidity between -2.4 and 2.4. The total area of the histogram is normalised to 1.
This work reports femtoscopic correlations of p$-$p ($\bar{\rm p}-\bar{\rm p}$) and p$-$d ($\bar{\rm p}-\bar{\rm d}$) pairs measured in Pb$-$Pb collisions at center-of-mass energy $\sqrt{s_{\rm NN}}$ = 5.02 TeV by the ALICE Collaboration. A fit to the measured proton-proton correlation functions allows one to extract the dependence of the nucleon femtoscopic radius of the particle-emitting source on the pair transverse mass ($m_\text{T}$) and on the average charge particle multiplicity $\langle\text{dN}_\text{ch}/\text{d}\eta\rangle^{1/3}$ for three centrality intervals (0$-$10$\%$, 10$-$30$\%$, 30$-$50$\%$). In both cases, the expected power-law and linear scalings are observed, respectively. The measured p$-$d correlations can be described by both two- and three-body calculations, indicating that the femtoscopy observable is not sensitive to the short-distance features of the dynamics of the p$-$(p$-$n) system, due to the large inter-particle distances in Pb$-$Pb collisions at the LHC. Indeed, in this study, the minimum measured femtoscopic source sizes for protons and deuterons have a minimum value at $2.73^{+0.05}_{-0.05}$ and $3.10^{+1.04}_{-0.86}$ fm, respectively, for the 30$-$50$\%$ centrality collisions. Moreover, the $m_{\rm{T}}$-scaling obtained for the p$-$p and p$-$d systems is compatible within 1$\sigma$ of the uncertainties. These findings provide new input for fundamental studies on the production of light (anti)nuclei under extreme conditions.
proton-proton (same charge) correlation function for centrality 0-10% from Pb-Pb collisions at 5020 GeV
proton-proton (same charge) correlation function for centrality 10-30% from Pb-Pb collisions at 5020 GeV
proton-proton (same charge) correlation function for centrality 30-50% from Pb-Pb collisions at 5020 GeV
Forum