There is strong evidence for the formation of small droplets of quark-gluon plasma in $p/d/^{3}$He+Au collisions at the Relativistic Heavy Ion Collider (RHIC) and in $p$+$p$/Pb collisions at the Large Hadron Collider. In particular, the analysis of data at RHIC for different geometries obtained by varying the projectile size and shape has proven insightful. In the present analysis, we find excellent agreement with the previously published PHENIX at RHIC results on elliptical and triangular flow with an independent analysis via the two-particle correlation method, which has quite different systematic uncertainties and an independent code base. In addition, the results are extended to other detector combinations with different kinematic (pseudorapidity) coverage. These results provide additional constraints on contributions from nonflow and longitudinal decorrelations.
$v_2$ vs $p_T$, p+Au at 200 GeV, 0-5% central, BBCS-FVTXS-CNT detector combination
$v_2$ vs $p_T$, d+Au at 200 GeV, 0-5% central, BBCS-FVTXS-CNT detector combination
$v_2$ vs $p_T$, 3He+Au at 200 GeV, 0-5% central, BBCS-FVTXS-CNT detector combination
Collective behaviour of final-state hadrons, and multiparton interactions are studied in high-multiplicity $ep$ scattering at a centre-of-mass energy $\sqrt{s}=318$ GeV with the ZEUS detector at HERA. Two- and four-particle azimuthal correlations, as well as multiplicity, transverse momentum, and pseudorapidity distributions for charged-particle multiplicities $N_{\textrm ch} \geq 20$ are measured. The dependence of two-particle correlations on the virtuality of the exchanged photon shows a clear transition from photoproduction to neutral current deep inelastic scattering. For the multiplicities studied, neither the measurements in photoproduction processes nor those in neutral current deep inelastic scattering indicate significant collective behaviour of the kind observed in high-multiplicity hadronic collisions at RHIC and the LHC. Comparisons of PYTHIA predictions with the measurements in photoproduction strongly indicate the presence of multiparton interactions from hadronic fluctuations of the exchanged photon.
Two-particle correlations $c_{1}\{2\}$ versus $Q^2$. Photoproduction data are shown at $Q^2$ = 0 GeV$^2$, while NC DIS is for $Q^2$ > 5 GeV$^2$.
Two-particle correlations $c_{1}\{2\}$ versus $Q^2$ with a rapidity separation: $\Delta \eta > 2$. Photoproduction data are shown at $Q^2$ = 0 GeV$^2$, while NC DIS is for $Q^2$ > 5 GeV$^2$.
Two-particle correlations $c_{1}\{2\}$ versus $Q^2$ with a high-$p_{\textrm{T}}$ constraint: $p_{\textrm{T}}$ > 0.5 GeV. Photoproduction data are shown at $Q^2$ = 0 GeV$^2$, while NC DIS is for $Q^2$ > 5 GeV$^2$.
In particle collider experiments, elementary particle interactions with large momentum transfer produce quarks and gluons (known as partons) whose evolution is governed by the strong force, as described by the theory of quantum chromodynamics (QCD). These partons subsequently emit further partons in a process that can be described as a parton shower which culminates in the formation of detectable hadrons. Studying the pattern of the parton shower is one of the key experimental tools for testing QCD. This pattern is expected to depend on the mass of the initiating parton, through a phenomenon known as the dead-cone effect, which predicts a suppression of the gluon spectrum emitted by a heavy quark of mass $m_{\rm{Q}}$ and energy $E$, within a cone of angular size $m_{\rm{Q}}$/$E$ around the emitter. Previously, a direct observation of the dead-cone effect in QCD had not been possible, owing to the challenge of reconstructing the cascading quarks and gluons from the experimentally accessible hadrons. We report the direct observation of the QCD dead cone by using new iterative declustering techniques to reconstruct the parton shower of charm quarks. This result confirms a fundamental feature of QCD. Furthermore, the measurement of a dead-cone angle constitutes a direct experimental observation of the non-zero mass of the charm quark, which is a fundamental constant in the standard model of particle physics.
The $R(\theta)$ variable for charm/inclusive emissions in three bins of $E_{Rad}$: 5-10, 10-20 and 20-35 GeV.
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.
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.
A search for the flavor-changing neutral-current decay $B^{+}\to K^{+}\nu\bar{\nu}$ is performed at the Belle II experiment at the SuperKEKB asymmetric energy electron-positron collider. The results are based on a data sample corresponding to an integrated luminosity of $63\,\mbox{fb}^{-1}$ collected at the $\Upsilon{(4S)}$ resonance and a sample of $9\,\mbox{fb}^{-1}$ collected at an energy $60\mathrm{\,Me\kern -0.1em V}$ below the resonance. A novel measurement method is employed, which exploits topological properties of the $B^{+}\to K^{+}\nu\bar{\nu}$ decay that differ from both generic bottom-meson decays and light-quark pair production. This inclusive tagging approach offers a higher signal efficiency compared to previous searches. No significant signal is observed. An upper limit on the branching fraction of $B^{+}\to K^{+}\nu\bar{\nu}$ of $4.1 \times 10^{-5}$ is set at the 90% confidence level.
- - - - - - - - Overview of HEPData Record - - - - - - - - <br/><br/> </ul> <b>Post-fit yields:</b> <ul> <li><a href="130199?version=1&table=Postfit%20yields%20Y(4S)">Y(4S)</a> <li><a href="130199?version=1&table=Postfit%20yields%20off-resonance">Off-resonance</a> </ul> <b>Exclusion limit:</b> <ul> <li><a href="130199?version=1&table=Expected%20and%20observed%20Limit">Expected limit and observed limit</a> </ul> <b>Efficiency:</b> <ul> <li><a href="130199?version=1&table=Selection%20efficiency">Selection efficiency as a function of $q^{2}$</a> </ul>
Yields in on-resonance data and as predicted by the simultaneous fit to the on- and off-resonance data, corresponding to an integrated luminosity of 63 and 9 fb$^{−1}$, respectively. The predicted yields are shown individually for charged and neutral B-meson decays and the five continuum background categories. The leftmost three bins belong to the first control region (CR1) with BDT$_{2} \in [0.93; 0.95]$ and the other nine bins correspond to the signal region (SR), three for each range of BDT$_{2} \in [0.95; 0.97; 0.99; 1.0]$. Each set of three bins is defined by $p_{T}(K^{+}) \in [0.5; 2.0; 2.4; 3.5] \rm{GeV}/c^{2}$.
Yields in off-resonance data and as predicted by the simultaneous fit to the on- and off-resonance data, corresponding to an integrated luminosity of 63 and 9 fb$^{−1}$, respectively. The predicted yields are shown individually for the five continuum background categories. The leftmost three bins belong to the third control region (CR3) with BDT$_{2} \in [0.93; 0.95]$ and the other nine bins correspond to the second control region (CR2), three for each range of BDT$_{2} \in [0.95; 0.97; 0.99; 1.0]$. Each set of three bins is defined by $p_{T}(K^{+}) \in [0.5; 2.0; 2.4; 3.5] \rm{GeV}/c^{2}$.
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.
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.
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.
Likelihood function from the fit to the nonresonant $B^+$ --> $K^+\ell^+ \ell^−$ candidates profiled as a function of $R_K$.
The PHENIX experiment at the Relativistic Heavy Ion Collider measured $\pi^0$ and $\eta$ mesons at midrapidity in U$+$U collisions at $\sqrt{s_{_{NN}}}=192$ GeV in a wide transverse momentum range. Measurements were performed in the $\pi^0(\eta)\rightarrow\gamma\gamma$ decay modes. A strong suppression of $\pi^0$ and $\eta$ meson production at high transverse momentum was observed in central U$+$U collisions relative to binary scaled $p$$+$$p$ results. Yields of $\pi^0$ and $\eta$ mesons measured in U$+$U collisions show similar suppression pattern to the ones measured in Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV for similar numbers of participant nucleons. The $\eta$/$\pi^0$ ratios do not show dependence on centrality or transverse momentum, and are consistent with previously measured values in hadron-hadron, hadron-nucleus, nucleus-nucleus, and $e^+e^-$ collisions.
$\pi^0$ spectra from figure 2a from minimum bias U+U collisions. Type A uncertainties are uncorrelated point-to-point. Type B uncertainties are correlated point-to-point. Type C uncertainties affect the scale of the data.
$\pi^0$ spectra from figure 2a from 0-20% U+U collisions. Type A uncertainties are uncorrelated point-to-point. Type B uncertainties are correlated point-to-point. Type C uncertainties affect the scale of the data.
$\pi^0$ spectra from figure 2a from 20-40% U+U collisions. Type A uncertainties are uncorrelated point-to-point. Type B uncertainties are correlated point-to-point. Type C uncertainties affect the scale of the data.
We present direct photon-hadron correlations in 200 GeV/A Au+Au, d+Au, and p+p collisions, for direct photon pT from 5–12 GeV/c, collected by the PHENIX Collaboration in the years from 2006 to 2011. We observe no significant modification of jet fragmentation in d+Au collisions, indicating that cold nuclear matter effects are small or absent. Hadrons carrying a large fraction of the quark's momentum are suppressed in Au+Au compared to p+p and d+Au. As the momentum fraction decreases, the yield of hadrons in Au+Au increases to an excess over the yield in p+p collisions. The excess is at large angles and at low hadron pT and is most pronounced for hadrons associated with lower momentum direct photons. Comparison to theoretical calculations suggests that the hadron excess arises from medium response to energy deposited by jets.
Per-trigger yield of hadrons associated to direct photons in Au+Au collisions for direct photon $p_T$ 5-9 GeV/$c$, compared with p+p baseline, in various $\xi$ bins.
Per-trigger yield of hadrons associated to direct photons in d+Au collisions for direct photon $p_T$ 7-9 GeV/$c$, compared with p+p baseline, in various $\xi$ bins.
Integrated away-side $\gamma_{dir}$-h per-trigger yields of Au+Au, d+Au, and p+p, as a function of $\xi$.
The PHENIX experiment has measured the spin alignment for inclusive $J/\psi\rightarrow e^{+}e^{-}$ decays in $p$+$p$ collisions at $\sqrt{s}=510$ GeV at midrapidity. The angular distributions have been measured in three different polarization frames, and the three decay angular coefficients have been extracted in a full two-dimensional analysis. Previously, PHENIX saw large longitudinal net polarization at forward rapidity at the same collision energy. This analysis at midrapidity, complementary to the previous PHENIX results, sees no sizable polarization in the measured transverse momentum range of $0.0
$\lambda_{\theta}$ measured in $J/\psi$ transverse momentum bins of 0.0 < $p_T$ < 3.0 GeV/$c$ and 3.0 < $p_T$ < 10.0 GeV/$c$ overlaid with NRQCD predictions in the Helicity and Collins-Soper frames.
$\lambda_{\theta}$ measured in $J/\psi$ transverse momentum bins of 0.0 < $p_T$ < 3.0 GeV/$c$ and 3.0 < $p_T$ < 10.0 GeV/$c$ overlaid with NRQCD predictions in the Helicity and Collins-Soper frames.
$\lambda_{\phi}$ measured in $J/\psi$ transverse momentum bins of 0.0 < $p_T$ < 3.0 GeV/$c$ and 3.0 < $p_T$ < 10.0 GeV/$c$ overlaid with NRQCD predictions in the Helicity and Collins-Soper frames.
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