New data on the inclusive production of the non-strange resonances ϱ0(770), ω(783), ϕ(1020) andf(1270) inK− p interactions at 32 GeV/c are presented. The inclusive production cross sections are equal to (4.32±0.72) mb, (3.7±1.4) mb, (0.65±0.10) mb and (0.91±0.35) mb respectively. Estimates of the topological cross sections are also obtained. The invariant and non-invariantx-distributions for the vector mesons ϱ0 and ϕ indicate the prevalence of forward resonance production in the c.m. system. For the tensorf-meson the rapidity andx-distributions are presented. Thet′-distributions for ϱ0, ϕ, andf have exponential slopes of 0.6±0.1 GeV−2, 1.2±0.2 GeV−2, and 0.8±0.5 GeV−2 respectively. The exponential slope ofpT2-distribution of thef-meson is equal to (2.3±0.5) GeV−2.
We perform a low-mass dark matter search using an exposure of 30\,kg$\times$yr with the XENON100 detector. By dropping the requirement of a scintillation signal and using only the ionization signal to determine the interaction energy, we lowered the energy threshold for detection to 0.7\,keV for nuclear recoils. No dark matter detection can be claimed because a complete background model cannot be constructed without a primary scintillation signal. Instead, we compute an upper limit on the WIMP-nucleon scattering cross section under the assumption that every event passing our selection criteria could be a signal event. Using an energy interval from 0.7\,keV to 9.1\,keV, we derive a limit on the spin-independent WIMP-nucleon cross section that excludes WIMPs with a mass of 6\,GeV/$c^2$ above $1.4 \times 10^{-41}$\,cm$^2$ at 90\% confidence level.
A study of π − p → K ∗ Λ and π − p → K ∗ Σ° at 3.9 GeV /c indicates that the main features of both reactions can be interpreted in terms of simple exchange processes, the first involving both natural and unnatural exchange, the second showing evidence for natural parity exchange only.
The ratio of the top-quark branching fractions $R = B(t \to Wb)/B(t \to Wq)$, where the denominator includes the sum over all down-type quarks (q = b, s, d), is measured in the $t\bar{t}$ dilepton final state with proton-proton collision data at $\sqrt{s}$ = 8 TeV from an integrated luminosity of 19.7 inverse-femtobarns, collected with the CMS detector. In order to quantify the purity of the signal sample, the cross section is measured by fitting the observed jet multiplicity, thereby constraining the signal and background contributions. By counting the number of b jets per event, an unconstrained value of R = 1.014 $\pm$ 0.003 (stat) $\pm$ 0.032 (syst) is measured, in good agreement with the standard model prediction. A lower limit R greater than 0.955 at the 95% confidence level is obtained after requiring R lower than one, and a lower limit on the Cabibbo-Kobayashi-Maskawa matrix element |$V_tb$| greater than 0.975 is set at 95% confidence level. The result is combined with a previous CMS measurement of the t-channel single-top-quark cross section to determine the top-quark total decay width, $\Gamma_t$ = 1.36 $\pm$ 0.02 (stat)$^{+0.14}_{-0.11}$ (syst) GeV.
The measured TOP TOPBAR production cross section.
The measured ratio of branching fractions, R = BR(TOP --> W BOTTOM) / BR(TOP --> W QUARK) where the denominator includes the sum over all down-type quarks (QUARK = BOTTOM, STRANGE, DOWN). The combined measurement and the individual measurements from the three channels considered are presented.
An indirect measurement of the top-quark total decay width.
Results are reported for the ${\rm B_s^0}\to\mu^+\mu^-$ branching fraction and effective lifetime and from a search for the decay ${\rm B^0}\to\mu^+\mu^-$. The analysis uses a data sample of proton-proton collisions accumulated by the CMS experiment in 2011, 2012, and 2016, with center-of-mass energies (integrated luminosities) of 7 TeV (5 fb$^{-1}$), 8 TeV (20 fb$^{-1}$), and 13 TeV (36 fb$^{-1}$). The branching fractions are determined by measuring efficiency-corrected event yields relative to ${\rm B^+}\to{\rm J}/\psi {\rm K^+}$ decays (with ${\rm J}/\psi\to\mu^+\mu^-$), which results in the cancellation of many of the systematic uncertainties. The decay ${\rm B_s^0}\to\mu^+\mu^-$ is observed with a branching fraction of ${\cal B}({\rm B_s^0}\to\mu^+\mu^-) = {[2.9^{+0.7}_{-0.6}\,(\text{exp})\pm{0.2}\,(\text{frag})]\times10^{-9}}$, where frag refers to the uncertainty in the ratio $f_s/f_u$ of the ${\rm B_s^0}$ and the ${\rm B^+}$ fragmentation functions, corresponding to a significance of 5.6 standard deviations. No significant excess is observed for the decay ${\rm B^0}\to\mu^+\mu^-$, and the upper limit ${\cal B}({\rm B^0}\to\mu^+\mu^-) < {3.6\times10^{-10}}$ is obtained at $95\%$ confidence level. These measured branching fractions are consistent with standard model predictions, and they supersede previous results from CMS based on the 2011 and 2012 data only. Finally, the ${\rm B_s^0}\to\mu^+\mu^-$ effective lifetime is measured, for the first time in CMS, and is found to be $\tau_{\mu^+\mu^-} = {1.70^{+0.61}_{-0.44}}$ ps.
Summary of the fitted yields for $B_{s}^{0}\rightarrow \mu^{+}\mu^{-}$ for all 14 categories of the 3D UML branching fraction fit.
None
No description provided.
Differential cross sections for the processes e + e − → e + e − (Bhabha scattering) and e + e − → γγ have been measured with the TOPAZ detector at s =52 GeV . The results agree with the predictions of quantum electrodynamics (QED). The lower limits for the QED cut-off parameters have been obtained to be Λ + ⩾115 GeV and Λ − ⩾236 GeV for Bhabha scattering, and Λ + ⩾94 GeV and Λ − ⩾59 GeV for the reaction e + e − → γγ .
Statistical errors only.
Statistical errors only.
Ratio of experimental data to prediction for lowest order QED. Statistical errors only.
In an analysis of a 2.92~fb$^{-1}$ data sample taken at 3.773~GeV with the BESIII detector operated at the BEPCII collider, we measure the absolute decay branching fractions to be $\mathcal B(D^0 \to K^-e^+\nu_e)=(3.505\pm 0.014 \pm 0.033)\%$ and $\mathcal B(D^0 \to \pi^-e^+\nu_e)=(0.295\pm 0.004\pm 0.003)\%$. From a study of the differential decay rates we obtain the products of hadronic form factor and the magnitude of the CKM matrix element $f_{+}^K(0)|V_{cs}|=0.7172\pm0.0025\pm 0.0035$ and $f_{+}^{\pi}(0)|V_{cd}|=0.1435\pm0.0018\pm 0.0009$. Combining these products with the values of $|V_{cs(d)}|$ from the SM constraint fit, we extract the hadronic form factors $f^K_+(0) = 0.7368\pm0.0026\pm 0.0036$ and $f^\pi_+(0) = 0.6372\pm0.0080\pm 0.0044$, and their ratio $f_+^{\pi}(0)/f_+^{K}(0)=0.8649\pm 0.0112\pm 0.0073$. These form factors and their ratio are used to test unquenched Lattice QCD calculations of the form factors and a light cone sum rule (LCSR) calculation of their ratio. The measured value of $f_+^{K(\pi)}(0) |V_{cs(d)}|$ and the lattice QCD value for $f^{K(\pi)}_+(0)$ are used to extract values of the CKM matrix elements of $|V_{cs}|=0.9601 \pm 0.0033 \pm 0.0047 \pm 0.0239$ and $|V_{cd}|=0.2155 \pm 0.0027 \pm 0.0014 \pm 0.0094$, where the third errors are due to the uncertainties in lattice QCD calculations of the form factors. Using the LCSR value for $f_+^\pi(0)/f_+^K(0)$, we determine the ratio $|V_{cd}|/|V_{cs}|=0.238\pm 0.004\pm 0.002\pm 0.011$, where the third error is from the uncertainty in the LCSR normalization. In addition, we measure form factor parameters for three different theoretical models that describe the weak hadronic charged currents for these two semileptonic decays. All of these measurements are the most precise to date.
Summary of the range of each $q^2$ bin, the number of the observed events $N_{\rm observed}$, the number of produced events $N_{\rm produced}$, and the partial decay rate $\Delta\Gamma$ in each $q^2$ bin for $D^0\to K^-e^+\nu_e$ decays.
Summary of the range of each $q^2$ bin, the number of the observed events $N_{\rm observed}$, the number of produced events $N_{\rm produced}$, and the partial decay rate $\Delta\Gamma$ in each $q^2$ bin for $D^0\to \pi^-e^+\nu_e$ decays.
A search for direct pair production of top squarks in final states with two tau leptons, $b$-jets, and missing transverse momentum is presented. The analysis is based on proton-proton collision data at $\sqrt{s} = 13$ TeV corresponding to an integrated luminosity of 36.1 fb$^{-1}$ recorded with the ATLAS detector at the Large Hadron Collider in 2015 and 2016. Two exclusive channels with either two hadronically decaying tau leptons or one hadronically and one leptonically decaying tau lepton are considered. No significant deviation from the Standard Model predictions is observed in the data. The analysis results are interpreted in terms of model-independent limits and used to derive exclusion limits on the masses of the top squark $\tilde t_1$ and the tau slepton $\tilde \tau_1$ in a simplified model of supersymmetry with a nearly massless gravitino. In this model, masses up to $m(\tilde t_1) = 1.16$ TeV and $m(\tilde \tau_1) = 1.00$ TeV are excluded at 95% confidence level.
Distribution of m<sub>T2</sub> in the signal region of the lep-had channel before the respective selection requirements, indicated by the vertical line and arrow, are applied. The stacked histograms show the various SM background contributions. The total background from events with a fake tau lepton in the lep-had channel (fake τ<sub>had</sub> + e /μ) is obtained from the fake-factor method. The hatched band indicates the total statistical and systematic uncertainty in the SM background. The error bars on the black data points represent the statistical uncertainty in the data yields. The dashed line shows the expected additional yields from a benchmark signal model. The rightmost bin includes the overflow.
Distributions of E<sub>T</sub><sup>miss</sup> in the signal region of the lep-had channel before the respective selection requirements, indicated by the vertical line and arrow, are applied. The stacked histograms show the various SM background contributions. The total background from events with a fake tau lepton in the lep-had channel (fake τ<sub>had</sub> + e /μ) is obtained from the fake-factor method. The hatched band indicates the total statistical and systematic uncertainty in the SM background. The error bars on the black data points represent the statistical uncertainty in the data yields. The dashed line shows the expected additional yields from a benchmark signal model. The rightmost bin includes the overflow.
Distributions of m<sub>T2</sub> in the signal region of the had-had channel before the respective selection requirements, indicated by the vertical line and arrow, are applied. Here, τ<sub>1</sub> (τ<sub>2</sub>) refers to the leading (subleading) τ<sub>had</sub>. The stacked histograms show the various SM background contributions. The hatched band indicates the total statistical and systematic uncertainty in the SM background. The error bars on the black data points represent the statistical uncertainty in the data yields. The dashed line shows the expected additional yields from a benchmark signal model. The rightmost bin includes the overflow.
A first search for same-sign WW production via double-parton scattering is performed based on proton-proton collision data at a center-of-mass energy of 8 TeV using dimuon and electron-muon final states. The search is based on the analysis of data corresponding to an integrated luminosity of 19.7 fb$^{-1}$. No significant excess of events is observed above the expected single-parton scattering yields. A 95% confidence level upper limit of 0.32 pb is set on the inclusive cross section for same-sign WW production via the double-parton scattering process. This upper limit is used to place a 95% confidence level lower limit of 12.2 mb on the effective double-parton cross section parameter, closely related to the transverse distribution of partons in the proton. This limit on the effective cross section is consistent with previous measurements as well as with Monte Carlo event generator predictions.
Expected and observed upper limits on the cross section for inclusive same-sign WW production via DPS
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