A measurement is presented of a ratio observable that provides a measure of the azimuthal correlations among jets with large transverse momentum $p_\mathrm{T}$. This observable is measured in multijet events over the range of $p_\mathrm{T}$ = 360-3170 GeV based on data collected by the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 134 fb$^{-1}$. The results are compared with predictions from Monte Carlo parton-shower event generator simulations, as well as with fixed-order perturbative quantum chromodynamics (pQCD) predictions at next-to-leading-order (NLO) accuracy obtained with different parton distribution functions (PDFs) and corrected for nonperturbative and electroweak effects. Data and theory agree within uncertainties. From the comparison of the measured observable with the pQCD prediction obtained with the NNPDF3.1 NLO PDFs, the strong coupling at the Z boson mass scale is $\alpha_\mathrm{S}(m_\mathrm{Z})$ = 0.1177 $\pm$ 0.0013 (exp) $_{-0.0073}^{+0.0116}$ (theo) = 0.1177 $_{-0.0074}^{+0.0117}$, where the total uncertainty is dominated by the scale dependence of the fixed-order predictions. A test of the running of $\alpha_\mathrm{S}(m_\mathrm{Z})$ in the TeV region shows no deviation from the expected NLO pQCD behaviour.
Bin-to-bin correlation matrix for the $R_{\Delta\phi}(p_\mathrm{T})$ distribution at the particle level.
The $R_{\Delta\phi}(p_\mathrm{T})$ distribution at the particle level as a function of $p_\mathrm{T}$.
Nonperturbative corrections for the $R_{\Delta\phi}(p_\mathrm{T})$ distribution.
Using proton-proton collision data corresponding to an integrated luminosity of 140 fb$^{-1}$ collected by the CMS experiment at $\sqrt{s}$ = 13 TeV, the $\Lambda_\text{b}^0$$\to$ J/$\psi\Xi^-$K$^+$ decay is observed for the first time, with a statistical significance exceeding 5 standard deviations. The relative branching fraction, with respect to the $\Lambda_\text{b}^0$$\to$$\psi$(2S)$\Lambda$ decay, is measured to be $\mathcal{B}$($\Lambda_\text{b}^0$$\to$ J/$\psi\Xi^-$K$^+$) / $\mathcal{B}$( $\Lambda_\text{b}^0$$\to$$\psi$(2S)$\Lambda$) = [3.38 $\pm$ 1.02 $\pm$ 0.61 $\pm$ 0.03]%, where the first uncertainty is statistical, the second is systematic, and the third is related to the uncertainties in $\mathcal{B}$($\psi$(2S) $\to$ J/$\psi\pi^+\pi^-$) and $\mathcal{B}$($\Xi^-$ $\to$ $\Lambda\pi^-$).
The measured branching fraction ratio
The production cross-sections of $J/\psi$ mesons in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=5$ TeV are measured using a data sample corresponding to an integrated luminosity of $9.13\pm0.18~\text{pb}^{-1}$, collected by the LHCb experiment. The cross-sections are measured differentially as a function of transverse momentum, $p_{\text{T}}$, and rapidity, $y$, and separately for $J/\psi$ mesons produced promptly and from beauty hadron decays (nonprompt). With the assumption of unpolarised $J/\psi$ mesons, the production cross-sections integrated over the kinematic range $0<p_{\text{T}}<20~\text{GeV}/c$ and $2.0<y<4.5$ are $8.154\pm0.010\pm0.283~\mu\text{b}$ for prompt $J/\psi$ mesons and $0.820\pm0.003\pm0.034~\mu\text{b}$ for nonprompt $J/\psi$ mesons, where the first uncertainties are statistical and the second systematic. These cross-sections are compared with those at $\sqrt{s}=8$ TeV and $13$ TeV, and are used to update the measurement of the nuclear modification factor in proton-lead collisions for $J/\psi$ mesons at a centre-of-mass energy per nucleon pair of $\sqrt{s_{\text{NN}}}=5$ TeV. The results are compared with theoretical predictions.
Double-differential production cross-sections for prompt $J/\psi$ mesons in ($p_\text{T},y$) intervals. The first uncertainties are statistical, the second are correlated systematic uncertainties shared between intervals, the third are uncorrelated systematic uncertainties, and the last are correlated between $p_\text{T}$ intervals and uncorrelated between $y$ intervals.
Double-differential production cross-sections for nonprompt $J/\psi$ mesons in ($p_\text{T},y$) intervals. The first uncertainties are statistical, the second are correlated systematic uncertainties shared between intervals, the third are uncorrelated systematic uncertainties, and the last are correlated between $p_\text{T}$ intervals and uncorrelated between $y$ intervals.
Single-differential production cross-sections for prompt $J/\psi$ mesons as a function of $p_\text{T}$. The first uncertainties are statistical, the second are correlated systematic uncertainties shared between intervals, and the last are uncorrelated systematic uncertainties.
The fundamental building blocks of the proton, quarks and gluons, have been known for decades. However, we still have an incomplete theoretical and experimental understanding of how these particles and their dynamics give rise to the quantum bound state of the proton and its physical properties, such as for example its spin. The two up and the single down quarks that comprise the proton in the simplest picture account only for a few percent of the proton mass, the bulk of which is in the form of quark kinetic and potential energy and gluon energy from the strong force. An essential feature of this force, as described by quantum chromodynamics, is its ability to create matter-antimatter quark pairs inside the proton that exist only for a very short time. Their fleeting existence makes the antimatter quarks within protons difficult to study, but their existence is discernible in reactions where a matter-antimatter quark pair annihilates. In this picture of quark-antiquark creation by the strong force, the probability distributions as a function of momentum for the presence of up and down antimatter quarks should be nearly identical, since their masses are quite similar and small compared to the mass of the proton. In the present manuscript, we show evidence from muon pair production measurements that these distributions are significantly different, with more abundant down antimatter quarks than up antimatter quarks over a wide range of momentum. These results revive interest in several proposed mechanisms as the origin of this antimatter asymmetry in the proton that had been disfavored by the previous results and point to the future measurements that can distinguish between these mechanisms.
Cross section ratios $\sigma_{D}/2\sigma_{H}$ binned in $x_t$ with their statistical and systematic uncertainties and the average values for the kinematic variables of each $x_t$ bin. The cross section ratios are defined as the ratio of luminosity-corrected yields from the hydrogen and deuterium targets. The final column is the experimental resolution in $x_t$ as determined by Monte Carlo simulations.
Ratios of $\bar{d}(x)$ to $\bar{u}(x)$ with their upper and lower statistical and systematic uncertainties. The analysis was based on the present cross section ratio data, and next-to-leading order calculations of the Drell-Yan cross sections using CT18 parton distributions for all except the ratio of $\bar{d}(x)$ to $\bar{u}(x)$. The systematic uncertainty is fully correlated among all $x$ bins. The systematic uncertainty does not include a contribution from the choice of the base (CT18) pdf, which is small if added in quadrature to the other systematic uncertainties.
Ratios of $\mathbf{\sigma_D}$ to $\mathbf{2\sigma_H}$ as a function of $\mathbf{P_T}$. Ratios of $\sigma_D$ to $2\sigma_H$ with their statistical and systematic uncertainties as a function of transverse momentum, $P_T$. The cross section ratios are defined as the ratio of luminosity-corrected yields from the hydrogen and deuterium targets. The final column, $\delta P_T$ is the experimental resolution in $P_T$ as determined by Monte Carlo simulation.
Measurements are presented of the single-diffractive dijet cross section and the diffractive cross section as a function of the proton fractional momentum loss $\xi$ and the four-momentum transfer squared $t$. Both processes pp$\to$pX and pp$\to$Xp, ie with the proton scattering to either side of the interaction point, are measured, where X includes at least two jets; the results of the two processes are averaged. The analyses are based on data collected simultaneously with the CMS and TOTEM detectors at the LHC in proton-proton collisions at $\sqrt{s}$= 8 TeV during a dedicated run with $\beta^{\ast} =$ 90 m at low instantaneous luminosity and correspond to an integrated luminosity of 37.5 nb$^{-1}$. The single-diffractive dijet cross section $\sigma^\mathrm{pX}_{\mathrm{jj}}$, in the kinematic region $\xi \lt$ 0.1, 0.03 $\lt |$t$| \lt 1$ GeV$^2$, with at least two jets with transverse momentum $p_\mathrm{T} >$ 40 GeV, and pseudorapidity $|\eta| \lt$ 4.4, is 21.7$\pm$0.9 (stat)$^{+3.0}_{-3.3}$ (syst) $\pm$ 0.9 (lum) nb. The ratio of the single-diffractive to inclusive dijet yields, normalised per unit of $\xi$, is presented as a function of $x$, the longitudinal momentum fraction of the proton carried by the struck parton. The ratio in the kinematic region defined above, for $x$ values in the range $-$2.9 $\leq \log_{10} x \leq$$-$1.6, is $R = (\sigma^\mathrm{pX}_{\mathrm{jj}}/\Delta\xi)/\sigma_{\mathrm{jj}} =$ 0.025$\pm$0.001 (stat) $\pm$ 0.003 (syst), where $\sigma^\mathrm{pX}_{\mathrm{jj}}$ and $\sigma_{\mathrm{jj}}$ are the single-diffractive and inclusive dijet cross sections, respectively. The results are compared with predictions from models of diffractive and nondiffractive interactions. Monte Carlo predictions based on the HERA diffractive parton distribution functions agree well with the data when corrected for the effect of soft rescattering between the spectator partons.
Differential cross section as a function of $t$ for single-diffractive dijet production, in the kinematic region $\xi < 0.1$, $0.03 < \lvert t \rvert < 1\,\mathrm{GeV}^2$, with at least two jets with transverse momentum $p_{\mathrm{T}} > 40\,\mathrm{GeV}$, and pseudorapidity $\lvert \eta \rvert < 4.4$.
Differential cross section as a function of $\xi$ for single-diffractive dijet production, in the kinematic region $\xi < 0.1$, $0.03 < \lvert t \rvert < 1\,\mathrm{GeV}^2$, with at least two jets with transverse momentum $p_{\mathrm{T}} > 40\,\mathrm{GeV}$, and pseudorapidity $\lvert \eta \rvert < 4.4$.
Ratio per unit of $\xi$ of the single-diffractive and inclusive dijet cross sections in the region given by $\xi < 0.1$ and $0.03 < \lvert t \rvert < 1\,\mathrm{GeV}^2$, with at least two jets with transverse momentum $p_{\mathrm{T}} > 40\,\mathrm{GeV}$, and pseudorapidity $\lvert \eta \rvert < 4.4$.
The observation of the $\Lambda_\mathrm{b}^0 \to$J/$\psi \Lambda \phi$ decay is reported using proton-proton collision data collected at $\sqrt{s} =$ 13 TeV by the CMS experiment at the LHC in 2018, corresponding to an integrated luminosity of 60 fb$^{-1}$. The ratio of the branching fractions $\mathcal{B}(\Lambda_\mathrm{b}^0 \to$J/$\psi \Lambda \phi)/\mathcal{B}(\Lambda_\mathrm{b}^0\to\psi \Lambda)$ is measured to be (8.26$\pm$0.90 (stat) $\pm$ 0.68 (syst) $\pm$ 0.11 $(\mathcal{B}))\times $10$^{-2}$, where the first uncertainty is statistical, the second is systematic, and the last uncertainty reflects the uncertainties in the world-average branching fractions of $\phi$ and $\psi$(2S) decays to the reconstructed final states.
The measured ratio of branching fractions
The production of the $\Lambda$(1520) baryonic resonance has been measured at midrapidity in inelastic pp collisions at $\sqrt{s}$ = 7 TeV and in p-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV for non-single diffractive events and in multiplicity classes. The resonance is reconstructed through its hadronic decay channel $\Lambda$(1520) $\rightarrow$ pK$^{-}$ and the charge conjugate with the ALICE detector. The integrated yields and mean transverse momenta are calculated from the measured transverse momentum distributions in pp and p-Pb collisions. The mean transverse momenta follow mass ordering as previously observed for other hyperons in the same collision systems. A Blast-Wave function constrained by other light hadrons ($\pi$, K, K$_{\rm{S}}^0$, p, $\Lambda$) describes the shape of the $\Lambda$(1520) transverse momentum distribution up to 3.5 GeV/$c$ in p-Pb collisions. In the framework of this model, this observation suggests that the $\Lambda(1520)$ resonance participates in the same collective radial flow as other light hadrons. The ratio of the yield of $\Lambda(1520)$ to the yield of the ground state particle $\Lambda$ remains constant as a function of charged-particle multiplicity, suggesting that there is no net effect of the hadronic phase in p-Pb collisions on the $\Lambda$(1520) yield.
$p_{\rm T}$-differential yields of $\Lambda$(1520) (sum of particle and anti-particle states) at midrapidity in inelastic pp collisions at $\sqrt{s}$ $\mathrm{=}$ 7 TeV.
$p_{\rm T}$-differential yields of $\Lambda$(1520) (sum of particle and anti-particle states) in NSD p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ $\mathrm{=}$ 5.02 TeV. The uncertainty 'sys,$p_{\rm T}$-correlated' indicates the systematic uncertainty after removing the contributions of $p_{\rm T}$-uncorrelated uncertainty.
$p_{\rm T}$-differential yields of $\Lambda$(1520) (sum of particle and anti-particle states) in p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ $\mathrm{=}$ 5.02 TeV in multiplicity interval 0--20\%. The uncertainty 'sys,$p_{\rm T}$-correlated' indicates the systematic uncertainty after removing the contributions of $p_{\rm T}$-uncorrelated uncertainty.
The ratio of the cross sections for inclusive isolated-photon production in $pp$ collisions at centre-of-mass energies of 13 and 8 TeV is measured using the ATLAS detector at the LHC. The integrated luminosities of the 13 TeV and 8 TeV datasets are 3.2 fb$^{-1}$ and 20.2 fb$^{-1}$, respectively. The ratio is measured as a function of the photon transverse energy in different regions of the photon pseudorapidity. The predictions from next-to-leading-order perturbative QCD calculations are compared with the measured ratio. The experimental systematic uncertainties as well as the uncertainties affecting the predictions are evaluated taking into account the correlations between the two centre-of-mass energies, resulting in a reduction of up to a factor of $2.5$ ($5$) in the experimental (theoretical) systematic uncertainties. The predictions based on several parameterisations of the proton parton distribution functions agree with the data within the reduced experimental and theoretical uncertainties. In addition, this ratio to that of the fiducial cross sections for $Z$ boson production at 13 and 8 TeV using the decay channels $Z \rightarrow e^+e^-$ and $Z \rightarrow \mu^+\mu^-$ is made and compared with the theoretical predictions. In this double ratio, a further reduction of the experimental uncertainty is obtained because the uncertainties arising from the luminosity measurement cancel out. The predictions describe the measurements of the double ratio within the theoretical and experimental uncertainties.
Measured ratio of cross sections for inclusive isolated-photon production as a function of $E_{\rm T}^{\gamma}$ for $|\eta^{\gamma}|<0.6$.
Predicted ratio of cross sections for inclusive isolated-photon production as a function of $E_{\rm T}^{\gamma}$ for $|\eta^{\gamma}|<0.6$.
Measured ratio of cross sections for inclusive isolated-photon production as a function of $E_{\rm T}^{\gamma}$ for $0.6<|\eta^{\gamma}|<1.37$.
A search for resonant and non-resonant pair production of Higgs bosons in the $b\bar{b}\tau^+\tau^-$ final state is presented. The search uses 36.1 fb$^{-1}$ of $pp$ collision data with $\sqrt{s}= 13$ TeV recorded by the ATLAS experiment at the LHC in 2015 and 2016. The semileptonic and fully hadronic decays of the $\tau$-lepton pair are considered. No significant excess above the expected background is observed in the data. The cross-section times branching ratio for non-resonant Higgs boson pair production is constrained to be less than 30.9 fb, 12.7 times the Standard Model expectation, at 95% confidence level. The data are also analyzed to probe resonant Higgs boson pair production, constraining a model with an extended Higgs sector based on two doublets and a Randall-Sundrum bulk graviton model. Upper limits are placed on the resonant Higgs boson pair production cross-section times branching ratio, excluding resonances $X$ in the mass range $305~{\rm GeV} < m_X < 402~{\rm GeV}$ in the simplified hMSSM minimal supersymmetric model for $\tan\beta=2$ and excluding bulk Randall-Sundrum gravitons $G_{\mathrm{KK}}$ in the mass range $325~{\rm GeV} < m_{G_{\mathrm{KK}}} < 885~{\rm GeV}$ for $k/\overline{M}_{\mathrm{Pl}} = 1$.
Observed and expected limits at 95% CL on the cross-sections of RS Graviton to HH for k/MPl = 1 process
Observed and expected limits at 95% CL on the cross-sections of RS Graviton to HH for k/MPl = 2 process
Observed and expected limits at 95% CL on the cross-sections of hMSSM scalar X to HH process
A search for new resonances decaying into jets containing b-hadrons in $pp$ collisions with the ATLAS detector at the LHC is presented in the dijet mass range from 0.57 TeV to 7 TeV. The dataset corresponds to an integrated luminosity of up to 36.1 fb$^{-1}$ collected in 2015 and 2016 at $\sqrt{s} = 13$ TeV. No evidence of a significant excess of events above the smooth background shape is found. Upper cross-section limits and lower limits on the corresponding signal mass parameters for several types of signal hypotheses are provided at 95% CL. In addition, 95% CL upper limits are set on the cross-sections for new processes that would produce Gaussian-shaped signals in the di-b-jet mass distributions.
The per-event b-tagging efficiencies after the event selection, as a function of the reconstructed invariant mass, for both single b-tagged and double b-tagged categories. The efficiencies are shown for simulated event samples corresponding to seven different b and Z' resonance masses in the high-mass region.
The per-event b-tagging efficiencies after the event selection, as a function of the reconstructed invariant mass, for double b-tagged category. The efficiencies are shown for simulated event samples corresponding to four different Z' resonance masses in the low-mass region. The efficiencies of identifying an event with two b-jets at trigger level only (Online) and when requiring offline confirmation (Online+offline) are shown.
Dijet mass spectra after the background only fit with the background prediction in the inclusive 1-b-tag high-mass region.
Forum