A search is presented for lepton-flavor violating decays of the Higgs boson to $\mu\tau$ and e$\tau$. The data set corresponds to an integrated luminosity of 137 fb$^{-1}$ collected at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. No significant excess has been found, and the results are interpreted in terms of upper limits on lepton-flavor violating branching fractions of the Higgs boson. The observed (expected) upper limits on the branching fractions are, respectively, $\mathcal{B}($H $\to\mu\tau)$$\lt$ 0.15 (0.15)% and $\mathcal{B}($H$\to$e$\tau)$ $\lt$ 0.22 (0.16)% at 95% confidence level.
Observed (expected) 95% CL upper limits on $B(H\to\mu\tau)$ for each individual category and combined
Observed (expected) 95% CL upper limits on $B(H\to e\tau)$ for each individual category and combined
Summary of observed and expected upper limits at 95% CL, best fit branching fractions and corresponding constraints on Yukawa couplings for the $H\to\mu\tau$ and $H\to e\tau$ channels
Several models of physics beyond the Standard Model predict the existence of dark photons, light neutral particles decaying into collimated leptons or light hadrons. This paper presents a search for long-lived dark photons produced from the decay of a Higgs boson or a heavy scalar boson and decaying into displaced collimated Standard Model fermions. The search uses data corresponding to an integrated luminosity of 36.1 fb$^{-1}$ collected in proton-proton collisions at $\sqrt{s} =$ 13 TeV recorded in 2015-2016 with the ATLAS detector at the Large Hadron Collider. The observed number of events is consistent with the expected background, and limits on the production cross section times branching fraction as a function of the proper decay length of the dark photon are reported. A cross section times branching fraction above 4 pb is excluded for a Higgs boson decaying into two dark photons for dark-photon decay lengths between 1.5 mm and 307 mm.
Upper limits at 95% CL on the cross section times branching fraction for the process $H \to 2\gamma_d + X$ with $m_H$ = 125 GeV in the muon-muon final state.
Upper limits at 95% CL on the cross section times branching fraction for the process $H \to 4\gamma_d + X$ with $m_H$ = 125 GeV in the muon-muon final state.
Upper limits at 95% CL on the cross section times branching fraction for the process $H \to 2\gamma_d + X$ with $m_H$ = 800 GeV in the muon-muon final state.
Electroproduction of hadrons is studied in the kinematic region W < 2.8 GeV and 0.3 < Q 2 < 1.4 GeV 2 using the DESY streamer chamber. Prong cross sections, charged-particle multiplicities and inclusive π − distributions are presented. The average charged multiplicity is found to be independent of Q 2 in the Q 2 range studied here; however it is lower than in photoproduction. The fraction of forward π − is found to be significantly less in electroproduction than in photoproduction. The 〈 p ⊥ 2 〉 for inclusive π − is, for all x values, similar to that found in photoproduction.
No description provided.
No description provided.
No description provided.
Decays of the 125 GeV Higgs boson into a Z boson and a $\rho^0$(770) or $\phi$(1020) meson are searched for using proton-proton collision data collected by the CMS experiment at the LHC at $\sqrt{s} = $ 13 TeV. The analysed data set corresponds to an integrated luminosity of 137 fb$^{-1}$. Events are selected in which the Z boson decays into a pair of electrons or a pair of muons, and the $\rho$ and $\phi$ mesons decay into pairs of pions and kaons, respectively. No significant excess above the background model is observed. As different polarization states are possible for the decay products of the Z boson and $\rho$ or $\phi$ mesons, affecting the signal acceptance, scenarios in which the decays are longitudinally or transversely polarized are considered. Upper limits at the 95% confidence level on the Higgs boson branching fractions into Z$\rho$ and Z$\phi$ are determined to be 1.04-1.31% and 0.31-0.40%, respectively, where the ranges reflect the considered polarization scenarios; these values are 740-940 and 730-950 times larger than the respective standard model expectations. These results constitute the first experimental limits on the two decay channels.
Observed and expected 95% CL upper limits on B(H $\rightarrow$ Z$\rho$), for different polarizations.
Observed and expected 95% CL upper limits on B(H $\rightarrow$ Z$\phi$), for different polarizations.
Additional spin-0 particles appear in many extensions of the standard model. We search for long-lived spin-0 particles $S$ in $B$-meson decays mediated by a $b\to s$ quark transition in $e^+e^-$ collisions at the $\Upsilon(4S)$ resonance at the Belle II experiment. Based on a sample corresponding to an integrated luminosity of $189 \mathrm{\,fb}^{-1}$, we observe no evidence for signal. We set model-independent upper limits on the product of branching fractions $\mathrm{Br}(B^0\to K^*(892)^0(\to K^+\pi^-)S)\times \mathrm{Br}(S\to x^+x^-)$ and $\mathrm{Br}(B^+\to K^+S)\times \mathrm{Br}(S\to x^+x^-)$, where $x^+x^-$ indicates $e^+e^-, \mu^+\mu^-, \pi^+\pi^-$, or $K^+K^-$, as functions of $S$ mass and lifetime at the level of $10^{-7}$.
Expected and observed candidates for $\mathcal{B}($$B^+\to K^+S$$) \times$ $\mathcal{B}($$S\to e^+e^-$) as a function of the reduced mediator candidate mass.
Expected and observed candidates for $\mathcal{B}($$B^+\to K^+S$$) \times$ $\mathcal{B}($$S\to \mu^+\mu^-$) as a function of the reduced mediator candidate mass.
Expected and observed candidates for $\mathcal{B}($$B^+\to K^+S$$) \times$ $\mathcal{B}($$S\to \pi^+\pi^-$) as a function of the reduced mediator candidate mass.
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.
Decay correlation data for π − p → K ∗ Λ at 3.9 GeV /c are analyzed to determine the amplitude structure. We emphasize combinations of observables invariant under rotations between s and t channel frames.
B B production in π − -uranium interactions has been observed at 320 GeV beam energy looking at events with three muons in the final state. The cross section is found to be σ B B = 4.5±1.4±1.4 nb per nucleon (for a linear A -dependence) or σ B B = 17.6±5.5±5.5 nb per nucleon (assuming A 0.75 dependence). An estimate of x F distribution is given.
BEAUTY INCLUSIVE SPECTRA WAS ASSUMED TO BE E*D(SIG)/D(X)/D(PT**2) = EXP(-0.9*PT**2)*(1-ABS(X))**A. THE BEST FIT FOR A IS A = 2.5.
We have measured the inclusive electroproduction of positive and negative hadrons in the quark fragmentation region using the streamer chamber at DESY. Data are presented in terms of the variable z p = p / v in the kinematic region 1.8 < W < 2.8 GeV and 0.3 < Q 2 < 1.4 GeV 2 . The positive hadron distributions contain a strong proton component. After subtraction of the proton component and elastic rho events, the distribution (1/ σ tot ) d σ /d z p for positive and negative hadrons agrees well with the corresponding distribution from e + e − annihilation (DORIS data). This behaviour supports the validity of the quark-parton model at surprisingly low Q 2 and W .
No description provided.
The total cross sections of 18.7 GeV Σ − hyperons on protons and deutrons have been measured to be 34.0 ± 1.1 mb and 61.3 + 1.4 mb, respectively. The derived Σ − -neutron cross section is 30.0 ± 1.2 mb.
CROSS SECTIONS CORRECTED FOR FORWARD COULOMB AND NUCLEAR SCATTERING.
We report on charged hadron production in deuteron-gold reactions at sqrt(s_NN) = 200 GeV. Our measurements in the deuteron-direction cover 1.4 < eta < 2.2, referred to as forward rapidity, and in the gold-direction -2.0 < eta < -1.4, referred to as backward rapidity, and a transverse momentum range p_T = 0.5-4.0 GeV/c. We compare the relative yields for different deuteron-gold collision centrality classes. We observe a suppression relative to binary collision scaling at forward rapidity, sensitive to low momentum fraction (x) partons in the gold nucleus, and an enhancement at backward rapidity, sensitive to high momentum fraction partons in the gold nucleus.
$R_{cp}$ as a function of $p_T$ for Punch-Through Hadrons at forward rapidity and backward rapidity for different centrality classes. Systematic uncertainties which are point-to-point uncorrelated (sys-uncorr) and correlated (sys-corr) are shown.
$R_{cp}$ as a function of $p_T$ for Hadron Decay Muons at forward rapidity and backward rapidity for different centrality classes. Systematic uncertainties which are point-to-point uncorrelated (sys-uncorr) and correlated (sys-corr) are shown.
$R_{cp}$ as a function of $\eta$ for 1.5 < $p_T$ < 4.0 GeV/$c$ for different centrality classes. Systematic uncertainties which are point-to-point uncorrelated (sys-uncorr) and correlated (sys-corr) are shown.
Correlations of charged hadrons of 1 < pT < 10 GeV/c with high pT direct photons and pi^ 0 mesons in the range 5 <pT < 15 GeV/c are used to study jet fragmentation in the photon+jet and di-jet channels, respectively. The magnitude of the partonic transverse momentum, kT, is obtained by comparing to a model incorporating a Gaussian kT smearing. The sensitivity of the associated charged hadron spectra to the underlying fragmentation function is tested and the data are compared to calculations using recent global fit results. The shape of the direct photon-associated hadron spectrum as well as its charge asymmetry are found to be consistent with a sample dominated by quark-gluon Compton scattering. No significant evidence of fragmentation photon correlated production is observed within experimental uncertainties.
Away-side charged hadron yield per π 0 trigger as a function of xE, which is equivalent to zT in the collinear limit cos(∆φ) = 1 & Away-side isolated direct photon trigger as a function of xE, which is equivalent to zT in the collinear limit cos(∆φ) = 1.
Away-side charged hadron yield per π 0 trigger as a function of xE, which is equivalent to zT in the collinear limit cos(∆φ) = 1 & Away-side isolated direct photon trigger as a function of xE, which is equivalent to zT in the collinear limit cos(∆φ) = 1.
Away-side charged hadron yield per π 0 trigger as a function of xE, which is equivalent to zT in the collinear limit cos(∆φ) = 1 & Away-side isolated direct photon trigger as a function of xE, which is equivalent to zT in the collinear limit cos(∆φ) = 1.
We determine the ratio of the partial decay width for ψ(3684)→μ+μ− to that for the cascade decay ψ(3684)→ψ(3095)+X to be (1.4 ± 0.3)% and, by direct observation of associated charged particles and γ rays, find the ratio of the partial decay width for ψ(3684)→ψ(3095)+π0π0 to that for ψ(3684)→ψ(3095)+π+π− to be 0.64 ± 0.15.
Axis error includes +- 20/20 contribution (UNKNOWN SYSTEMATICAL ERRORDECAY-BR(BRN=J/PSI(3097) --> MU+ MU-, BR=?, C=FOLDED)).
Axis error includes +- 20/20 contribution (UNKNOWN SYSTEMATICAL ERRORDECAY-BR(BRN=J/PSI(3097) --> MU+ MU-, BR=?, C=FOLDED)).
We present results on Λc+ production in 29-GeV e+e− annihilation. The Λc+ are observed via their semileptonic decays to Λe+X and Λμ+X. With radiative corrections, we find σ(e+e−→Λc+X)〉BΛc+→eΛX)= 1.5±0.6±0.5 pb or 0.0038±0.0015±0.0012 Λc+→Λe+X decay per hadronic event, and σ(e+e−Λc+X)B(Λc+→μΛX)= 1.4±1.4±0.4 pb or 0.0035±0.0035±0.0011 Λc+→Λμ+X decay per hadronic event. These results can be used to place constraints on the predictions of various production models.
Cross sections * branching ratio for LAMBDA/C+ production in LAMBDA E+ decay channel.
Cross sections * branching ratio for LAMBDA/C+ production in LAMBDA MU+ decay channel.
We have measured the partial widths for the three reactions e + e − → Z 0 → e + e − , μ + μ − , τ + τ − . The results are Γ ee = 84.3±1.3 MeV, √ Γ ee Γ μμ =83.9±1.4 MeV, and √ Γ ee Γ ττ =83.9±1.4 MeV, where the errors are statistical. The systematic errors are estimated to be 1.0 MeV, 0.9 MeV, and 1.4 MeV, respectively. We perform a simultaneous fit to the cross sections for the e + e − →e + e − , μ + μ − , and τ + τ − data, the differential cross section as a function of polar angle for the electron data, and the forward- backward asymmetry for the muon data. We obtain the leptonic partial with Γ ℓℓ =84.0±0.9 (stat.) MeV. The systematic error is estimated to be 0.8 MeV. Also, we obtain the axial-vector and vector weak coupling constants of charged leptons, g A =−0.500±0.003 and g ν =−0.064 −0.013 +0.017 .
Cross section from 1990 data.
Visible cross section obtained using the cuts required by Method I (see text of paper). (1989 and 1990 data).
Visible cross section obtained using the cuts required by Method II (see text of paper). (1989 and 1990 data). RE = E+ E- --> E+ E- (GAMMA).
As part of a program to determine proton-proton elastic-scattering amplitudes, we have measured the spin-spin correlation parameter CNN at 6 GeV/c. Measurements were made over the |t| range of 0.08 to 1.4 (GeV/c)2 using a polarized beam and a polarized target at the Argonne National Laboratory Zero Gradient Synchrotron.
No description provided.
First measurements of the e + e − → π + π − K + K − cross section have been performed by the DM1 on DCI in the total energy range 1.4–2.18 GeV. π + π − K + K − production is dominated by K ∗ Kπ dynamics. The cross section is rather large around 1.9 GeV. Comparison with K 0 S inclusive production shows an isospin interference. Upper limits on φππ production are compatible with the OZI rule.
No description provided.
UPPER LIMITS TO PHI CROSS SECTIONS WITH CL=90 PCT.
The differential cross-section of the reaction γ p→ η p has been measured at the Deutsches Elektronen Synchrotron (DESY) at mean photon energies of 4 and 6 GeV in the momentum transfer range between zero and 1.4 GeV 2 . The data show a slight maximum around t =−0.15 GeV 2 and fall off smoothly till t =−1.4 GeV 2 . There is no indication of a dip around t =−0.5 GeV 2 .
Axis error includes +- 19/19 contribution.
Axis error includes +- 19/19 contribution.
Using a low background data sample of $9.7\times10^{5}$ $J\psi\rightarrow\gamma\eta^\prime$, $\eta^\prime\rightarrow\gamma\pi^+\pi^-$ events, which are 2 orders of magnitude larger than those from the previous experiments, recorded with the BESIII detector at BEPCII, the decay dynamics of $\eta^\prime\rightarrow\gamma\pi^+\pi^-$ are studied with both model-dependent and model-independent approaches. The contributions of $\omega$ and the $\rho(770)-\omega$ interference are observed for the first time in the decays $\eta^\prime\rightarrow\gamma\pi^+\pi^-$ in both approaches. Additionally, a contribution from the box anomaly or the $\rho(1450)$ resonance is required in the model-dependent approach, while the process specific part of the decay amplitude is determined in the model-independent approach.
Numbers of events selected (Column 2), numbers of background events from sideband (Column 3), efficiencies (Column 4), and resolution RMS (Column 5) for different $M_{\pi^+\pi^-}$ bins.
We have measured the mass of the Z boson to be 91.11±0.23 GeV/c2, and its width to be 1.61−0.43+0.60 GeV. If we constrain the visible width to its standard-model value, we find the partial width to invisible decay modes to be 0.62±0.23 GeV, corresponding to 3.8±1.4 neutrino species.
In this Letter, we report the first measurement of the inelastic cross section for antideuteron-nucleus interactions at low particle momenta, covering a range of $0.3 \leq p < 4$ GeV/$c$. The measurement is carried out using p-Pb collisions at a center-of-mass energy per nucleon-nucleon pair of $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV, recorded with the ALICE detector at the CERN LHC and utilizing the detector material as an absorber for antideuterons and antiprotons. The extracted raw primary antiparticle-to-particle ratios are compared to the results from detailed ALICE simulations based on the GEANT4 toolkit for the propagation of antiparticles through the detector material. The analysis of the raw primary (anti)proton spectra serves as a benchmark for this study, since their hadronic interaction cross sections are well constrained experimentally. The first measurement of the inelastic cross section for antideuteron-nucleus interactions averaged over the ALICE detector material with atomic mass numbers $\langle A \rangle$ = 17.4 and 31.8 is obtained. The measured inelastic cross section points to a possible excess with respect to the Glauber model parameterization used in GEANT4 in the lowest momentum interval of $0.3 \leq p < 0.47$ GeV/$c$ up to a factor 2.1. This result is relevant for the understanding of antimatter propagation and the contributions to antinuclei production from cosmic ray interactions within the interstellar medium. In addition, the momentum range covered by this measurement is of particular importance to evaluate signal predictions for indirect dark-matter searches.
Raw primary antiproton-to-proton ratio as a function of the momentum p_primary.
Raw primary antiproton-to-proton ratio from Geant4-based MC simulations as a function of the momentum p_primary.
Raw primary antideuteron-to-deuteron ratio as a function of the momentum p_primary.
The helicity-dependent single $\pi^{0}$ photoproduction cross section on the deuteron and the angular dependence of the double polarisation observable $E$ for the quasi-free single $\pi^0$ production off the proton and the neutron have been measured for the first time from the threshold region up to the photon energy 1.4 GeV. The experiment was performed at the tagged photon facility of the MAMI accelerator and used a circularly polarised photon beam and longitudinally polarised deuteron target. The reaction products were detected using the large acceptance Crystal Ball/TAPS calorimeter, which covered 97% of the full solid angle. Comparing the cross section from the deuteron with the sum of free nucleon cross sections provides a quantitative estimate of the effects of the nuclear medium on pion production. In contrast, comparison of $E$ helicity asymmetry data from quasi-free protons off deuterium with data from a free proton target indicates that nuclear effects do not significantly affect this observable. As a consequence, it is deduced that the helicity asymmetry $E$ on a free neutron can be reliably extracted from measurements on a deuteron in quasi-free kinematics.
Inclusive polarized total cross section as a function of photon beam energy.
Helicity-dependent differential cross section on deuteron at Egamma= 161. MeV
Helicity-dependent differential cross section on deuteron at Egamma= 178. MeV
This Letter presents a measurement of WZ production in 1.02 fb^-1 of pp collision data at sqrt(s) = 7 TeV collected by the ATLAS experiment in 2011. Doubly leptonic decay events are selected with electrons, muons and missing transverse momentum in the final state. In total 71 candidates are observed, with a background expectation of 12.1 +/- 1.4(stat.) +4.1/-2.0(syst) events. The total cross section for WZ production for Z gamma^* masses within the range 66 GeV to 116 GeV is determined to be sigma_WZ^tot = 20.5 +3.1/-2.8(stat.) +1.4/-1.3(syst.) +0.9/-0.8(lumi.)pb, which is consistent with the Standard Model expectation of 17.3 +1.3/-0.8 pb. Limits on anomalous triple gauge boson couplings are extracted.
Total fiducial cross-section $WZ\to\ell\nu\ell\ell$.
The first measurement of dielectron ($\mathrm{e}^{+}\mathrm{e}^{-}$) production in central (0$-$10$\%$) Pb-Pb collisions at $\mathbf{\sqrt{{\textit{s}}_{\mathrm{NN}}}}$ = 2.76 TeV at the LHC is presented. The dielectron invariant-mass spectrum is compared to the expected contributions from hadron decays in the invariant-mass range $0 < m_{\mathrm{ee}}<3.5\ \mathrm{GeV}/\textit{c}^{2}$. The ratio of data and the cocktail of hadronic contributions without vacuum $\rho^{0}$ is measured in the invariant-mass range $0.15 < m_{\mathrm{ee}}<0.7\ \mathrm{GeV}/\textit{c}^{2}$, where an excess of dielectrons is observed in other experiments, and its value is $1.40 \pm 0.28\ (\mathrm{stat.}) \pm 0.08\ (\mathrm{syst.}) \pm 0.27\ (\mathrm{cocktail})$. The dielectron spectrum measured in the invariant mass range $0 < m_{\mathrm{ee}}<1\ \mathrm{GeV}/\textit{c}^{2}$ is consistent with the predictions from two theoretical model calculations that include thermal dielectron production from both partonic and hadronic phases with in-medium broadened $\rho^{0}$ meson. The fraction of direct virtual photons over inclusive virtual photons is extracted for dielectron pairs with invariant mass $0.1 < m_{\mathrm{ee}}<0.3\ \mathrm{GeV}/\textit{c}^{2}$, and in the transverse-momentum intervals $1<p_{\mathrm{T}, \mathrm{ee}}<2\ \mathrm{GeV}/\textit{c}$ and $2<p_{\mathrm{T}, \mathrm{ee}}<4\ \mathrm{GeV}/\textit{c}$. The measured fraction of virtual direct photons is consistent with the measurement of real direct photons by ALICE and with the expectations from previous dielectron measurements at RHIC within the experimental uncertainties.
Dielectron invariant-mass spectrum measured in central Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV. The statistical and systematic uncertainties of the data are represented by vertical bars and boxes.
Data-to-cocktail ratio. Statistical uncertainties are represented by vertical bars and systematic uncertainties by boxes.
Dielectron invariant-mass spectrum divided by the hadronic cocktail without the contribution from the vacuum $\rho^{0}$. The statistical and systematic uncertainties of data are represented by vertical bars and boxes.
Using the ARGUS detector at DORIS II, we have studied the production of the charmed baryon Λ c in e + e − annihilation at centre-of-mass energies near 10 GeV. The Λ c + was seen in the three decay modes pK − π + , Λπ + π − π + and K̄ 0 p, with products of normalized cross section times branching ratio [ R ·Br] of (10.8±1.4±1.2)×10 −3 , 6.6±1.5±0.9)×10 −3 and (6.7±1.4±0.8)×10 −3 respectively. The measured mass for the Λ c was (2283.1±1.7±2.0) MeV/ c 2 . A limit on the decay rates to Λπ + is reported. The fragmentation function of the Λ c was measured.
No description provided.
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