First data are presented for the polarized-target asymmetry in the reaction π+p→π+pγ at an incident pion energy of 298 MeV. The geometry was chosen to maximize the sensitivity to the radiation of the magnetic dipole moment μΔ of the Δ++(1232 MeV). A fit of the asymmetry in the cross section d5σ/dΩπ dΩγ dk as a function of the photon energy k to predictions from a recent isobar-model calculation with μΔ as the only free parameter yields μΔ=1.64(±0.19expΔ,±0.14 theor)μp. Though this value agrees with bag-model corrections to the SU(6) prediction μΔ=2μp, further clarifications on the model dependence of the result are needed, in particular since the isobar model fails to describe both the cross section and the asymmetry at the highest photon energies.
No description provided.
No description provided.
We have measured the fivefold differential cross section d5σ/dΩπdΩγdEγ for the process π+p→π+pγ with incident pions of energy 299 MeV. The angular regions for the outgoing pions (55°≤θlabπ≤95°), and photons (θlabγ=241°±10°) in coplanar geometry are selected to maximize the sensitivity to the radiation from the magnetic dipole moment of the Δ++(1232) resonance. At low photon energies, the data agree with the soft-photon approximation to pion-proton bremsstrahlung. At forward pion angles the data agree with older data and with the latest theoretical calculations for 2.3μp≤μΔ≤3.3μp. However at more backward pion angles where no data existed, the predictions fail.
No description provided.
No description provided.
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.
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.
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.
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.
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.
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.
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.
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 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.
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.
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.
Measurements of multiple particle production at ADONE, the Frascati e + e − storage ring, have been carried out at C.M. energies 1.4 GeV to 2.4 GeV. The hadronic nature of the observed particles is discussed and a lower limit of 30 nbarn set for the total multiparticle cross section.
LOWER LIMIT FOR PRODUCTION OF AT LEAST TWO CHARGED HADRONS.
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
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.
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.
From 1.4 million hadronic Z decays collected by the ALEPH detector at LEP, an enriched sample of Z → cc̄ events is extracted by requiring the presence of a high momentum D ∗± . The charm quark forward-backward charge asymmetry at the Z pole is measured to be A FB 0. c = (8.0 ± 2.4) % corresponding to an effective electroweak mixing angle of sin 2 θ W eff = 0.2302 ± 0.0054.
Value of SIN2TW(eff) from CQ-quark asymmetries.
No description provided.
New measurements of thee + e − → π + π − π + π − cross section have been performed by the magnetic detector DM1 at DCI (ORSAY) in the 1.4−2.18 GeV total energy range with statistics of 11000 events. Assuming the4 π ± production is dominated by the ϱ′(1.6) we determine its parameters: M = 1.57 ± 0.02 (stat.) −0.00 +0.06 (syst.) GeV,Γ = 0.51 ± 0.04 (stat.) −0.01 +0.04 (syst.)GeV,Γ ρ ′ee B ϱ′→ ρ 0 π + π − = 2.67 ± 0.19 (stat.) −0.36 +0.27 (syst.)keV.
No description provided.
We report measurements of the polarization parameters in π+p and π−p elastic scattering at an incident momentum of 100 GeV/c. The results cover the range 0.18<~−t<~1.4 GeV2 and are in agreement with current Regge-model predictions.
No description provided.
No description provided.
No description provided.
Full angular distributions of the polarization parameter in elastic K+p scattering at 1.37, 1.45, 1.60, 1.71, 1.80, 1.89, 2.11, and 2.31 GeV/c are presented. These data were obtained in an experiment at the Zero Gradient Synchrotron using a polarized proton target with arrays of scintillation and Čerenkov counters to detect the scattered particles.
No description provided.
No description provided.
No description provided.
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 $WZ\to\ell\nu\ell\ell$.
A sample of about 1.4 million hadronic Z decays, selected among the data recorded by the DELPHI detector at LEP during 1994, was used to measure for the first time the momentum spectra of K + , K 0 , p , Λ and their antiparticles in gluon and quark jets. As observed for inclusive charged particles, the production spectra of identified particles were found to be softer in gluon jets than in quark jets, with a higher total multiplicity.
Y events.
Mercedes events.
The cross section of the pure QED process e + e − → γγ has been measured using data accumulated during the 1989 and 1990 scans of the Z 0 resonance at LEP. Both the energy dependence and the angular distribution are in good agreement with the QED prediction. Upper limits on the branching ratios of Z 0 → γγ , Z 0 → π 0 γ and Z 0 → ηγ have been set at 1.4×10 −4 , 1.4×10 −4 and 2.0×10 −4 respectively. Lower limits on the cutoff parameters of the modified electron propagator have been found to be Λ + > 117 GeV and Λ − > 110 GeV. The reaction e + e − → γγγ has also been studied and was found to be consistent with the QED prediction. An upper limit on the branching ratio of Z 0 → γγγ has been set at 6.6 × 10 −5 . All the limits are given at 95% confidence level.
No description provided.
No description provided.
No description provided.
The total cross section for gamma p -> 3pi0 p has been measured for the first time from threshold to 1.4 GeV using the tagged photon beam of the Mainz Microtron. The equipment utilized the Crystal Ball multiphoton spectrometer, the TAPS forward detector and a particle identification detector. The gamma p -> 3pi0 p total cross section has two broad enhancements at sqrt{s}~1.5 GeV and 1.7 GeV. We obtained the ratio of the total cross sections gamma p -> 3pi0 p to gamma p -> eta p equal to 0.014 \pm 0.001 at sqrt{s}~1.5 GeV.
The proof is given for the existence of the reaction e + e − → h ± h ∓ in the energy range 1400–2400 MeV, and its energy dependence is compared with that of e + e − → e ± e ∓ , in the same experimental conditions of observation. The exponent of the s -dependence of the ratio α = (e + e − → h ± h ∓ )/ (e + e − → e ± e ∓ ) is measured to be n = 2.08 ± 0.45, in the s -range (1.96 − 5.76) GeV 2 , on the basis of 51 e + e − → h ± h ∓ events and 8918 e + e − → e ± e ∓ events observed.
CROSS SECTION FOR PRODUCTION OF CHARGED HADRON PAIRS.
The reaction γp → K 0 Σ + has been measured with the SAPHIR detector at the electron stretcher ring ELSA. The total cross section rises up to a peak value of 1.1 μ b at a photon energy of 1.4 GeV. The differential cross sections dσ/dΩ are consistent with being flat throughout the measured energy range. The first measurement of the Σ + polarization in photon induced reactions was obtained.
Total cross section for the reaction GAMMA P --> K0 SIGMA+. Errors include statistics and the uncertainty on the acceptance calculation and photon flux.
Differential cross section for the reaction GAMMA P --> K0 SIGMA+. Errors are dominated by statistical uncertainties.
Measure of SIGMA+ polarization in the reaction GAMMA P --> K0 SIGMA+.
Results from the first PWA of the K + K − system produced by incident K − , are presented in the mass range from the threshold to 1.70 GeV. In the P and D waves only the φ and f′ mesons are observed and their production mechanism studied. A broad S wave peaking at 1.4 GeV is observed but the lack of information about its phase makes the search for new 0 ++ mesons inconclusive.
ASSUMING BRANCHING RATIO 0.486 FOR PHI --> K+ K-.
No description provided.
No description provided.
Excitation functions of proton-proton elastic scattering cross sections have been measured in narrow steps for projectile momenta pp (energies Tp) from 1100 to 3300MeV/c (500 to 2500 MeV) in the angular range 35°≤Θc.m.≤90° with a detector providing ΔΘc.m.≈1.4° resolution. Measurements have been performed continuously during projectile acceleration in the cooler synchrotron COSY with an internal CH2 fiber target, taking particular care to monitor luminosity as a function of Tp. The advantages of this experimental technique are demonstrated, and the excitation functions obtained are compared to existing cross section data. No evidence for narrow structures was found.
No description provided.
No description provided.
No description provided.
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.
The observation of 21 K + K − pairs in 38 hadron pair events produced at 1.5, 1.6, and 1.7 GeV total centre-of-mass energies in e + e − annihilations, establishes that time-like photons produce K pairs and π pairs with comparable rates in this energy range. The K-meson electromagnetic form factor at a mean s -value of 2.4 GeV 2 is measured to be | F K | = 0.50±0.08. The number of e + e − pairs observed in the same angular and energy range is 5148.
No description provided.
First measurements of the e + e − → K S 0 K ± π ∓ reaction in the 1.4–2.18 GeV energy range have been performed with the magnetic detector DM1 at the Orsay storage rings DCI. The cross section is rather large. The production is mainly K ∗0 K 0 which reveals an interference between isovector and isoscalar amplitudes. These results show again the existence of an isoscalar vector at 1.65 GeV shown to be a φ ′ meson.
No description provided.
The results of an experiment performed at Adone, the 2×1.5-GeV e+e− Frascati storage ring, are presented. During ∼ 1500 hours of running time a total of 5164 electron-positron elastic scattering events (integrated luminosity L=3.5×1035 cm−2) and 605 noncoplanar events from the reaction e+e−→a±+b±+anything (effective integrated luminosity L=2.5×1035 cm−2) have been collected at c.m. energies ranging from 1.4 to 2.4 GeV. Over the energy range explored (1.4-2.4 GeV), corresponding to an average q2 ranging from 0.8 to 2.4 (GeV/c)2, the yield of wide-angle (60°<θ<120°) electron-positron elastic scattering events is found to be in good agreement with the predictions of quantum electrodynamics (QED) (R=σexpσQED=1.05±0.04). The noncoplanar events appear to be of a hadronic nature and are produced with a much higher cross section than predicted on the basis of ρ, ω, φ dominance at these energies. The total cross section for the reaction e+e−→a±b±+anything shows a rapid increase to ∼ 90 nb between 1.0 and 1.5 GeV and falls off slowly to ∼ 50 nb at 2.4 GeV. Cross sections for some of the channels contributing to this multihadron process (e+e−→π+π−π+π−, e+e−→π+π−π+π−+neutrals, e+e−→3π+3π−) have been determined and are reported.
DATA VALUES MEASURED FROM GRAPH IN JOURNAL.
VALUES OF R CALCULATED FROM TOTAL CROSS SECTION.
The reactions e + e − → ρη , ρπ , φπ and φη have been studied with the magnetic detector DM1 at DCI in the total energy ranges between 1.4 and 2.18 GeV. The ρη signal is clearly seen. Upper limits for ρπ and φη channels as well as for the OZI forbidden φπ channel.
No description provided.
UPPER LIMIT TO SIG AS EXPLAINED IN SYSTEMATICS.
UPPER LIMIT TO CROSS SECTION AT CL=90 PCT.
Differential cross-sections for proton-proton elastic scattering have been measured covering the angular range from 50° to 90° c.m. at twelve incident momenta from 1.3 to 3.0 GeV/c. The angular distributions are quite smooth, but there is evidence of structure in the energy dependence of fixed-angle cross-sections at |t| ∼ 1 (GeV)2.
No description provided.
No description provided.
No description provided.
The total cross section of the pp→ pp η reaction has been measured at incident proton energies of 1.265, 1.3, 1.4 and 1.5 GeV by detecting the two photons from the η decay in the PINOT spectrometer. The data are compared with other near-threshold measurements and with the predictions of existing theoretical calculations.
Value given at 1263 MeV assumes energy 2 MeV lower than nominal value. This uncertainty only affects this lowest energy point.
The reaction γ+p→π++n has been measured for incident γ-ray energies from 0.7 to 8 GeV and recoil lab angles from 170° to 180° using the Cornell 10-GeV synchrotron. The data presented here cover the transition region between the resonance region and the high-energy region studied at SLAC. The results are compared with various phenomenological Regge-pole analyses and with similar data on π0 photoproduction taken at DESY.
No description provided.
No description provided.
Using data samples collected at center of mass energies of $\sqrt{s}$ = 4.009, 4.226, 4.257, 4.358, 4.416 and 4.599 GeV with the BESIII detector operating at the BEPCII storage ring, we search for the isospin violating decay $Y(4260)\rightarrow J/\psi \eta \pi^{0}$. No signal is observed, and upper limits on the cross section $\sigma(e^{+}e^{-}\rightarrow J/\psi \eta \pi^{0})$ at the 90\% confidence level are determined to be 3.6, 1.7, 2.4, 1.4, 0.9 and 1.9 pb, respectively.
Results on $e^{+}e^{-}\rightarrow J/\psi\eta\pi^{0}$. Listed in the table are the integrated luminosity $\cal{L}$, radiative correction factor (1+$\delta^{r}$) taken from QED calculation assuming the $Y(4260)$ cross section follows a Breit$-$Wigner line shape, vacuum polarization factor (1+$\delta^{v}$), average efficiency ($\epsilon^{ee}{\cal B}^{ee}$ + $\epsilon^{\mu\mu}{\cal B}^{\mu\mu}$), number of observed events $N^\text{obs}$, number of estimated background events $N^\text{bkg}$, the efficiency corrected upper limits on the number of signal events $N^\text{up}$, and upper limits on the Born cross section $\sigma^\text{Born}_\text{UL}$ (at the 90 $\%$ C.L.) at each energy point.
We present a measurement of the inclusive jet cross section in p¯p collisions at √s =1.8 TeV at the Fermilab Tevatron using the Collider Detector at Fermilab. Good agreement is seen with the predictions of recent next-to-leading-order [O(αs3)] QCD predictions. The dependence of the cross section on clustering cone size is reported for the first time. An improved limit on Λc, a term characterizing possible quark substructure, is set at 1.4 TeV (95% C.L.).
Data are averaged over the pseudorapidity interval 0.1 to 0.7.
Measurements of the ZZ production cross sections in proton-proton collisions at center-of-mass energies of 7 and 8 TeV are presented. Candidate events for the leptonic decay mode ZZ to 2 l 2 nu, where l denotes an electron or a muon, are reconstructed and selected from data corresponding to an integrated luminosity of 5.1 (19.6) inverse femtobarns at 7 (8) TeV collected with the CMS experiment. The measured cross sections, sigma(pp to ZZ) = 5.1 -1.4 +1.5 (stat) -1.1 +1.4 (syst) +/- 0.1 (lumi) pb at 7 TeV, and 7.2 -0.8 +0.8 (stat.) -1.5 +1.9 (syst) +/- 0.2 (lumi) pb at 8 TeV, are in good agreement with the standard model predictions with next-to-leading-order accuracy. The selected data are analyzed to search for anomalous triple gauge couplings involving the ZZ final state. In the absence of any deviation from the standard model predictions, limits are set on the relevant parameters. These limits are then combined with the previously published CMS results for ZZ in 4 l final states, yielding the most stringent constraints on the anomalous couplings.
Using a maximum-likelihood fit to the reduced-MET data distributions, with all the systematic uncertainties incorporated as nuisance parameters, we obtain the following cross sections for the pp->ZZ process (with both Z bosons in the mass range 60-120 GeV). The first systematic uncertainty is the combined systematic uncertainty excluding luminosity, the second is the luminosity. The theory calculations are 6.2+0.3-0.2 pb at 7 TeV and 7.6+0.4-0.3 pb at 8 TeV, including NLO QCD and NLO EW corrections.
We have measured the inclusive prompt electron cross section over a wide momentum range (P>0.5 GeV/c) with the PEP-4 TPC detector. The semielectronic branching fractions of thec andb quarks are (9.1±0.9 (stat.)±1.3 (syst.))% and (11.0±1.8±1.0)%, respectively. Theb quark fragmentation function peaks at highz with 〈zb〉=0.74±0.05±0.03. The axial couplings to the neutral current areac=2.3±1.4±1.0 for thec quark andab=−2.0±1.9±0.5 for theb quark.
No description provided.
No description provided.
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The NuTeV experiment at Fermilab has used a sign-selected neutrino beam to perform a search for the lepton number violating process $\bar{\nu}_mu e^- \to \mu^- \bar{\nu}_e$, and to measure the cross-section of the Standard Model inverse muon decay process $\nu_{\mu} e^- \to \mu^- \nu_e$. NuTeV measures the inverse muon decay asymptotic cross-section $\sigma/E$ to be 13.8 $\pm$ 1.2 $\pm$ 1.4 x $10^{-42} cm^2$/GeV. The experiment also observes no evidence for lepton number violation and places one of the most restrictive limits on the LNV/IMD cross-section ratio at $\sigma (\bar{\nu}_{\mu} e^- \to \mu^- \bar{\nu}_e) /\sigma (\nu_{\mu}e^- \to \mu^- \nu_e$) $\le$ 1.7% at 90% C.L. for V-A couplings and $\le$ 0.6% for scalar couplings.
No description provided.
No description provided.
Using the 18.8 pb −1 of data accumulated at LEP in 1990 and 1991 with the ALEPH detector, a direct test of neutral current CP -invariance is performed by a search for CP -odd correlations in Z decays to τ pairs where both τ decay modes are identified. No evidence for CP -violation is observed. The weak dipole moment of the τ has been measured to be d τ ( m Z ) = (1.3 ± 1.4 ± 0.1) × 10 −17 e ·cm which results in an upper limit on the weak dipole moment of | d τ ( m Z )| ⩽ 3.7 × 10 −17 e ·cm with 95% confidence level.
No description provided.
We have measured the total cross sections of Ω− and Ω¯+ forward (xF>~0) inclusive production in KL0-carbon interactions in the range EK0=80 to 280 GeV to be 3.5±1.4 and 2.4±1.0 μb, respectively. We observe that the xF distributions for both of these states are increasing from xF=0 to xF≈0.6. The p⊥2 distributions are described as an exponential function in p⊥ with an average p⊥2 of 0.540 GeV2/c2.
Based on a sample of 22 four-prong D 0 / D 0 decays produced in hydrogen by 360 GeV/ c π − , we present the following new results: mean lifetime τ = (3.5 −0.9 +1.4 ) x 10 −13 s ; production cross section for x F > 0.0, σ = (10.3 ± 3.5) ωb ; the D → K ± π ± π + π − branching ratio = (7.1 ± 2.5)%.
No description provided.
We report the first observation of two narrow charmed strange baryons decaying to $\Xi_c^+\gamma$ and $\Xi_c^0\gamma$, respectively, using data from the CLEO II detector at CESR. We interpret the observed signals as the $\Xi_c^{+\prime}(c{su})$ and $\Xi_c^{0\prime}(c{sd})$, the symmetric partners of the well-established antisymmetric $\Xi_c^+(c[su])$ and $\Xi_c^0(c[sd])$. The mass differences $M(\Xi_c^{+\prime})-M(\Xi_c^+)$ and $M(\Xi_c^{0\prime})-M(\Xi_c^0)$ are measured to be $107.8\pm 1.7\pm 2.5$ and $107.0\pm 1.4\pm 2.5 MeV/c^2$, respectively.
The data for two resonances are combined together.
CONST(NAME=EPS) is the parameter of the Peterson fragmentation function (C.Peterson et al., PR D27, 105 (1983)) D(N)/D(Z) = FD(Z) = const * (1/Z)*1/(1 - (1/Z)-CONST(NAME=EPS)/(1-Z))**2. The data for two resonances are combined together.
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