In Phys. Lett. B 753, 629-638 (2016) [arXiv:1507.08188] the BESIII collaboration published a cross section measurement of the process $e^+e^-\to \pi^+ \pi^-$ in the energy range between 600 and 900 MeV. In this erratum we report a corrected evaluation of the statistical errors in terms of a fully propagated covariance matrix. The correction also yields a reduced statistical uncertainty for the hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon, which now reads as $a_\mu^{\pi\pi\mathrm{, LO}}(600 - 900\,\mathrm{MeV}) = (368.2 \pm 1.5_{\rm stat} \pm 3.3_{\rm syst})\times 10^{-10}$. The central values of the cross section measurement and of $a_\mu^{\pi\pi\mathrm{, LO}}$, as well as the systematic uncertainties remain unchanged.
Results of the BESIII measurement of the cross section $\sigma^{\rm bare}_{\pi^+\pi^-(\gamma_{\rm FSR})} \equiv \sigma^{\rm bare}(e^+e^-\rightarrow\pi^+\pi^-(\gamma_{\rm FSR}))$ and the squared pion form factor $|F_\pi|^2$. The errors are statistical only. The value of $\sqrt{s'}$ represents the bin center. The 0.9$\%$ systematic uncertainty is fully correlated between any two bins.
Results for the bare cross section $\sigma^\text{bare}_{\pi^+\pi^-}$ and the pion form factor together with their statistical uncertainties. The systematical uncertainties are given by 0.9% (see <a href="https://inspirehep.net/literature/1385603">arXiv:1507.08188</a>).
Bare cross section $\sigma^\mathrm{bare}(e^+e^-\to\pi^+\pi^-(\gamma_\mathrm{FSR}))$ of the process $e^+e^-\to\pi^+\pi^-$ measured using the initial state radiation method. The data is corrected concerning final state radiation and vacuum polarization effects. The final state radiation is added using the Schwinger term at born level.
The exclusive electroproduction of J/psi mesons, ep->epJ/psi, has been studied with the ZEUS detector at HERA for virtualities of the exchanged photon in the ranges 0.15<Q^2<0.8 GeV^2 and 2<Q^2<100 GeV^2 using integrated luminosities of 69 pb^-1 and 83 pb^-1, respectively.The photon-proton centre-of-mass energy was in the range 30<W<220 GeV and the squared four-momentum transfer at the proton vertex |t|<1.The cross sections and decay angular distributions are presented as functions of Q^2, W and t. The effective parameters of the Pomeron trajectory are in agreement with those found in J/psi photoproduction. The spin-density matrix elements, calculated from the decay angular distributions, are consistent with the hypothesis of s-channel helicity conservation. The ratio of the longitudinal to transverse cross sections, sigma_L/sigma_T, grows with Q^2, whilst no dependence on W or t is observed. The results are in agreement with perturbative QCD calculations and exhibit a strong sensitivity to the gluon distribution in the proton.
Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 0.15 to 0.18 GeV**2.
Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 2 to 5 GeV**2.
Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 5 to 10 GeV**2.
None
NORMALISATION UNCERTAINTY IS 7 PCT.
NORMALISATION UNCERTAINTY IS 7 PCT.
This paper completes the detailed presentation of our PV experiment on the 6S1/2 - 7S1/2 transition in Cs. A detailed description of the data acquisition and processing is given. The results of two independent measurements made on ΔF = 0 and ΔF =1 hfs components agree, providing an important cross-check. After a complete reanalysis of systematics and calibration, the precision is slightly improved, leading to the weighted average Im Epv 1/β = - 1.52 ± 0.18 mV/cm. Later results from an independent group agree quite well. With the semi-empirical value β = (26.8 ± 0.8) a30, our result yields Epv1 = (- 0.79 ± 0.10) x 10-11 i |e|a0. Coupled with the atomic calculations, this implies that the weak nuclear charge of Cs is Qw = -68 ± 9. This value agrees with the standard electroweak theory and leads to a weak interaction angle sin2 θ W = 0.21 ± 0.04. The complementarity of these measurements with high energy experiments is illustrated.
Revision of the earlier experiment PL 117B, 358. (7s)2S1/2:F=4 --> (6s)2S1/2:F=4 transition.
Revision of the earlier experiment PL 134B, 463. (7s)2S1/2:F=3 --> (6s)2S1/2:F=4 transition.
Combined of the two above measurements following the philosophy: quadratic sum of the statistical and systematic uncertainties and weighting each result by the squared reciprocal of that uncertainty. (7s)2S1/2 --> (6s)2S1/2 transitions.
Electron-proton elastic scattering cross sections have been measured at squared four-momentum transfers q 2 of 0.67, 1.00, 1.17, 1.50, 1.75, 2.33 and 3.00 (GeV/ c ) 2 and Electron scattering angles θ e between 10° and 20° and at about 86° in the laboratory. The proton electromagnetic form factors G E p and G M p were determined. The results indicate that G E p ( q 2 ) decreases faster with increasing q 2 than G M p ( q 2 ). Quasi-elastic electron-deuteron cross sections have been determined at values of q 2 = 0.39, 0.565, 0.78, 1.0 and 1.5 (GeV/ c ) 2 and scattering angles between 10° and 12°. At q 2 = 0.565 (GeV/ c 2 data have also been taken with θ e = 35° and at q 2 = 1.0 and 1.5 (GeV/ c ) 2 with θ e = 86°. Electron-proton as well as electron-neutron scattering cross sections have been deduced by the ratio method. The theoretical uncertainties of this procedure are shown to be small by comparison of the bound with the free proton cross sections. The magnetic form factor of the neutron G M n derived from the data is consistent with the scaling law. The charge form factor of the neutron is found to be small.
Axis error includes +- 2.1/2.1 contribution (NORMALISATION ERROR).
Axis error includes +- 2.1/2.1 contribution (NORMALISATION ERROR).
Axis error includes +- 2.1/2.1 contribution (NORMALISATION ERROR).
We present the analysis of the inclusive $K^{0}$ production in p+p and p+Nb collisions measured with the HADES detector at a beam kinetic energy of 3.5 GeV. Data are compared to the GiBUU transport model. The data suggest the presence of a repulsive momentum-dependent kaon potential as predicted by the Chiral Perturbation Theory (ChPT). For the kaon at rest and at normal nuclear density, the ChPT potential amounts to $\approx 35$ MeV. A detailed tuning of the kaon production cross sections implemented in the model has been carried out to reproduce the experimental data measured in p+p collisions. The uncertainties in the parameters of the model were examined with respect to the sensitivity of the experimental results from p+Nb collisions to the in-medium kaon potential.
The K0 production cross section in P P collisions.
The K0 production cross section in P + NB collisions. The uncertainty given on SIG(P NB --> K0 X) is the dominating absolute normalization uncertainty.
We present a measurement of the cross section for hadron production by e+e− annihilation in the vicinity of the previously observed resonance near 3.77 GeV. The data are used to determine the parameters of the ψ(3770) resonance. The values found are: mass, 3764±5 MeV/c2, total width, 23.5±5 MeV, and partial width to electron pairs, 276±50 eV.
THESE RESULTS ARE ALSO IN THE THESIS OF R. H. SCHINDLER, SLAC-219 (1979), THE RECORD OF WHICH CONTAINS THE TABULATED CROSS SECTIONS.
BREIT-WIGNER RESONANCE PLUS BACKGROUND FIT TO RADIATIVELY CORRECTED DATA YIELDS RESONANCE MASS OF 3764 +- 5 MEV, TOTAL WIDTH OF 23.5 +- 5 MEV AND PARTIAL WIDTH TO ELECTRON PAIRS OF 276 +- 50 EV.
PEAK CROSS SECTION FOR D MESON PAIR PRODUCTION AT PSI(3770) RESONANCE. J/PSI, PSI(3684) AND CONTINUUM BACKGROUND (R=2.5) SUBTRACTED.
The differential cross section for the process $\gamma \gamma \to \eta \pi^0$ has been measured in the kinematic range $0.84 \GeV < W < 4.0 \GeV$, $|\cos \theta^*|<0.8$, where $W$ and $\theta^*$ are the energy and $\pi^0$ (or $\eta$) scattering angle, respectively, in the $\gamma\gamma$ center-of-mass system. The results are based on a 223 fb$^{-1}$ data sample collected with the Belle detector at the KEKB $e^+ e^-$ collider. Clear peaks due to the $a_0(980)$ and $a_2(1320)$ are visible. The differential cross sections are fitted in the energy region $0.9 \GeV < W < 1.46 \GeV$ to obtain the parameters of the $a_0(980)$. Its mass, width and $\Gamma_{\gamma \gamma} \B (\eta \pi^0)$ are measured to be $982.3 ^{+0.6}_{-0.7} ^{+3.1}_{-4.7} \MeV/c^2$, $75.6 \pm 1.6 ^{+17.4}_{-10.0} \MeV$ and $128 ^{+3}_{-2} ^{+502}_{-43} \eV$, respectively. The energy and angular dependences above 3.1 GeV are compared with those measured in the $\pi^0 \pi^0$ channel. The integrated cross section over $|\cos \theta^*|<0.8$ has a $W^{-n}$ dependence with $n = 10.5 \pm 1.2 \pm 0.5$, which is slightly larger than that for $\pi^0 \pi^0$. The differential cross sections show a $\sin^{-4} \theta^*$ dependence similar to $\gamma \gamma \to \pi^0 \pi^0$. The measured cross section ratio, $\sigma(\eta \pi^0)/\sigma(\pi^0 \pi^0) = 0.48 \pm 0.05 \pm 0.04$, is consistent with a QCD-based prediction.
The total cross section integrated over ABS(COS(THETA*)) < 0.8.
The differential cross section as a function of angle for W = 0.85 GeV.
The differential cross section as a function of angle for W = 0.87 GeV.
The production of two high-p_T jets in the interactions of quasi-real photons in e+e- collisions at sqrt{s_ee} from 189 GeV to 209 GeV is studied with data corresponding to an integrated e+e- luminosity of 550 pb^{-1}. The jets reconstructed by the k_T cluster algorithm are defined within the pseudo-rapidity range -1 < eta < 1 and with jet transverse momentum, p_T, above 3 GeV/c. The differential di-jet cross-section is measured as a function of the mean transverse momentum ptmean of the jets and is compared to perturbative QCD calculations.
Total cross section for dijet production. Errors are combined statistics and systematics.
Measured dijet production cross section as a function of the mean jet transverse momentum. Errors include both statistics and systematics.
Measured dijet production cross section as a function of jet pseudorapiditydifference. Errors include both statistics and systematics.
Three-jet production in deep inelastic ep scattering and photoproduction was investigated with the ZEUS detector at HERA using an integrated luminosity of 127 pb-1. Measurements of differential cross sections are presented as functions of angular correlations between the three jets in the final state and the proton-beam direction. These correlations provide a stringent test of perturbative QCD and show sensitivity to the contributions from different colour configurations. Fixed-order perturbative QCD calculations assuming the values of the colour factors C_F, C_A and T_F as derived from a variety of gauge groups were compared to the measurements to study the underlying gauge group symmetry. The measured angular correlations in the deep inelastic ep scattering and photoproduction regimes are consistent with the admixture of colour configurations as predicted by SU(3) and disfavour other symmetry groups, such as SU(N) in the limit of large N.
Integrated 3-jet photoproduction cross section.
Integrated 3-jet cross sections in NC DIS.
Normalized differential 3-jet photoproduction cross section as a function of THETA(H).
We report a high-statistics measurement of differential cross sections for the process gamma gamma -> pi^0 pi^0 in the kinematic range 0.6 GeV <= W <= 4.0 GeV and |cos theta*| <= 0.8, where W and theta* are the energy and pion scattering angle, respectively, in the gamma gamma center-of-mass system. Differential cross sections are fitted to obtain information on S, D_0, D_2, G_0 and G_2 waves. The G waves are important above W ~= 1.6 GeV. For W <= 1.6 GeV the D_2 wave is dominated by the f_2(1270) resonance while the S wave requires at least one additional resonance besides the f_0(980), which may be the f_0(1370) or f_0(1500). The differential cross sections are fitted with a simple parameterization to determine the parameters (the mass, total width and Gamma_{gamma gamma}B(f_0 -> pi^0 pi^0)) of this scalar meson as well as the f_0(980). The helicity 0 fraction of the f_2(1270) meson, taking into account interference for the first time, is also obtained.
Differential cross section for W = 0.61, 0.63 and 0.65 GeV.
Differential cross section for W = 0.67, 0.69 and 0.71 GeV.
Differential cross section for W = 0.73, 0.75 and 0.77 GeV.
Using the CLEO-c detector at the Cornell Electron Storage Ring, we have measured inclusive and exclusive cross sections for the production of D+, D0 and Ds+ mesons in e+e- annihilations at thirteen center-of-mass energies between 3.97 and 4.26 GeV. Exclusive cross sections are presented for final states consisting of two charm mesons (DD, D*D, D*D*, Ds+Ds-, Ds*+Ds-, and Ds*+Ds*-) and for processes in which the charm-meson pair is accompanied by a pion. No enhancement in any final state is observed at the energy of the Y(4260).
Exclusive cross section for two body neutral non-strange charm mesons.
Exclusive cross section for two body charged non-strange charm mesons.
Exclusive cross section for two body strange charm mesons.
$K^0_SK^0_S$ production in two-photon collisions has been studied using a 397.6 fb$^{-1}$ data sample collected with the Belle detector at the KEKB $e^+e^-$ collider. For the first time the cross sections are measured in the two-photon center-of-mass energy range between 2.4 GeV and 4.0 GeV and angular range $|\cos\theta^*|<0.6$. Combining the results with measurements of $\gamma\gamma\to K^+K^-$ from Belle, we observe that the cross section ratio $\sigma(K^0_SK^0_S)/\sigma(K^+K^-)$ decreases from ~0.13 to ~0.01 with increasing energy. Signals for the $\chi_{c0}$ and $\chi_{c2}$ charmonium states are also observed.
Total cross section for the process GAMMA GAMMA --> K0S K0S.
Angular distribution of the cross section in the W range 2.4 to 2.5 GeV.
Angular distribution of the cross section in the W range 2.5 to 2.6 GeV.
Charm production in deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 82 pb^{-1}. Charm has been tagged by reconstructing D^{*+}, D^0, D^{+} and D_s^+ (+ c.c.) charm mesons. The charm hadrons were measured in the kinematic range p_T(D^{*+},D^0,D^{+}) > 3 GeV, p_T(D_s^+)>2 GeV and |\eta(D)| < 1.6 for 1.5 < Q^2 < 1000 GeV^2 and 0.02 < y < 0.7. The production cross sections were used to extract charm fragmentation ratios and the fraction of c quarks hadronising into a particular charm meson in the kinematic range considered. The cross sections were compared to the predictions of next-to-leading-order QCD, and extrapolated to the full kinematic region in p_T(D) and \eta(D) in order to determine the open-charm contribution, F_2^{c\bar{c}}(x,Q^2), to the proton structure function F_2.
Production cross section for all D0 mesons, those not originating fom D* decays and those originating from D* decays.
Production cross section for additional D* mesons (not decaying to D0) and all D* mesons.
Production cross section for D+ mesons.
The production of energetic neutrons in $ep$ collisions has been studied with the ZEUS detector at HERA. The neutron energy and $p_T^2$ distributions were measured with a forward neutron calorimeter and tracker in a $40 \pb^{-1}$ sample of inclusive deep inelastic scattering (DIS) data and a $6 \pb^{-1}$ sample of photoproduction data. The neutron yield in photoproduction is suppressed relative to DIS for the lower neutron energies and the neutrons have a steeper $p_T^2$ distribution, consistent with the expectation from absorption models. The distributions are compared to HERA measurements of leading protons. The neutron energy and transverse-momentum distributions in DIS are compared to Monte Carlo simulations and to the predictions of particle exchange models. Models of pion exchange incorporating absorption and additional secondary meson exchanges give a good description of the data.
Ratio of leading neutron to inclusive cross sections integrated to the full PT range.
Normalized double differential cross sections for leading neutron production for the full DIS sample. Statistical errors only are given.
Normalized double differential cross sections for leading neutron production for the full DIS sample. Statistical errors only are given.
The dependence of the photon structure on the photon virtuality, Q^2, is studied by measuring the reaction e^+p\to e^+ + {\rm jet} + {\rm jet} + {\rm X} at photon-proton centre-of-mass energies 134 < W < 223 GeV. Events have been selected in the Q^2 ranges \approx 0 GeV^2, 0.1-0.55 GeV^2, and 1.5-4.5 GeV^2, having two jets with transverse energy E_T^{jet} > 5.5 GeV in the final state. The dijet cross section has been measured as a function of the fractional momentum of the photon participating in the hard process, x_gamma. The ratio of the dijet cross section with x_gamma < 0.75 to that with x_gamma > 0.75 decreases as Q^2 increases. The data are compared with the predictions of NLO pQCD and leading-order Monte Carlo programs using various parton distribution functions of the photon. The measurements can be interpreted in terms of a resolved photon component that falls with Q^2 but remains present at values of Q^2 up to 4.5 GeV^2. However, none of the models considered gives a good description of the data.
Dijet cross section for the low ET set of cuts.
Dijet cross section for the high ET set of cuts.
Ratio of Dijet cross sections as a function of Q**2 for XOBS(C=GAMMA) less than to greater than 0.75 for the lower ET cuts.
We report on a high statistics measurement of the total and differential cross sections of the process gamma gamma -> pi^+ pi^- in the pi^+ pi^- invariant mass range 0.8 GeV/c^2 < W < 1.5 GeV/c^2 with 85.9 fb^{-1} of data collected at sqrt{s}=10.58 GeV and 10.52 GeV with the Belle detector. A clear signal of the f_0(980) resonance is observed in addition to the f_2(1270) resonance. An improved 90% confidence level upper limit Br.(eta'(958) -> pi^+ pi^-) < 2.9 x 10^{-3} is obtained for P- and CP-violating decay of the eta'(958) meson using the most conservative assumption about the interference with the background.
Total cross section.
No description provided.
No description provided.
A detailed analysis is presented of the diffractive deep-inelastic scattering process $ep\to eXY$, where $Y$ is a proton or a low mass proton excitation carrying a fraction $1 - \xpom > 0.95$ of the incident proton longitudinal momentum and the squared four-momentum transfer at the proton vertex satisfies $|t|<1 {\rm GeV^2}$. Using data taken by the H1 experiment, the cross section is measured for photon virtualities in the range $3.5 \leq Q^2 \leq 1600 \rm GeV^2$, triple differentially in $\xpom$, $Q^2$ and $\beta = x / \xpom$, where $x$ is the Bjorken scaling variable. At low $\xpom$, the data are consistent with a factorisable $\xpom$ dependence, which can be described by the exchange of an effective pomeron trajectory with intercept $\alphapom(0)= 1.118 \pm 0.008 {\rm (exp.)} ^{+0.029}_{-0.010} {\rm (model)}$. Diffractive parton distribution functions and their uncertainties are determined from a next-to-leading order DGLAP QCD analysis of the $Q^2$ and $\beta$ dependences of the cross section. The resulting gluon distribution carries an integrated fraction of around 70% of the exchanged momentum in the $Q^2$ range studied. Total and differential cross sections are also measured for the diffractive charged current process $e^+ p \to \bar{\nu}_e XY$ and are found to be well described by predictions based on the diffractive parton distributions. The ratio of the diffractive to the inclusive neutral current $ep$ cross sections is studied. Over most of the kinematic range, this ratio shows no significant dependence on $Q^2$ at fixed $\xpom$ and $x$ or on $x$ at fixed $Q^2$ and $\beta$.
Reduced cross section from the Minimum Bias data sample taken in 1997.
Reduced cross section from the Minimum Bias data sample taken in 1997.
Reduced cross section from the complete ('all') data sample taken in 1997.
Measurements are presented of inclusive charm and beauty cross sections in e^+p collisions at HERA for values of photon virtuality 12 \le Q^2 \le 60 GeV^2 and of the Bjorken scaling variable 0.0002 \le x \le 0.005. The fractions of events containing charm and beauty quarks are determined using a method based on the impact parameter, in the transverse plane, of tracks to the primary vertex, as measured by the H1 vertex detector. Values for the structure functions F_2^{c\bar{c}} and F_2^{b\bar{b}} are obtained. This is the first measurement of F_2^{b\bar{b}} in this kinematic range. The results are found to be compatible with the predictions of perturbative quantum chromodynamics and withprevious measurements of F_2^{c\bar{c}}.
Measured NC reduced cross section for charm quarks.
Measuredstructure function F2 for charm quarks.
Measured NC reduced cross section for BOTTOM quarks.
The reaction $^2$H$(e,e^\prime p)n$ has been studied with full kinematic coverage for photon virtuality $1.75<Q^2<5.5$ GeV$^2$. Comparisons of experimental data with theory indicate that for very low values of neutron recoil momentum ($p_n<100$ MeV/c) the neutron is primarily a spectator and the reaction can be described by the plane-wave impulse approximation. For $100<p_n<750$ MeV/c proton-neutron rescattering dominates the cross section, while $\Delta$ production followed by the $N\Delta \to NN$ transition is the primary contribution at higher momenta.
Recoil neutron momentum distributions.
Recoil neutron angular distributions for neutron momenta in the range 400 to 600 MeV.
Recoil neutron angular distributions for neutron momenta in the range 200 to 300 MeV.
The production of the neutral strange hadrons $K^{0}_{S}$, $\Lambda$ and $\bar{\Lambda}$ has been measured in $ep$ collisions at HERA using the ZEUS detector. Cross sections, baryon-to-meson ratios, relative yields of strange and charged light hadrons, $\Lambda$ ($\bar{\Lambda}$) asymmetry and polarization have been measured in three kinematic regions: $Q^2 > 25 \gev^2$: $5 < Q^2 < 25 \gev^2$: and in photoproduction ($Q^2 \simeq 0$). In photoproduction the presence of two hadronic jets, each with at least $5 \gev$ transverse energy, was required. The measurements agree in general with Monte Carlo models and are consistent with measurements made at $e^+ e^-$ colliders, except for an enhancement of baryon relative to meson production in photoproduction.
Differential K0S cross section in DIS events as a function of transverse momentum (lab). for Q**2 from 5 to 25 GeV**2.
Differential K0S cross section in DIS events as a function of transverse momentum (lab). for Q**2 > 25 GeV**2.
Differential K0S cross section in DIS events as a function of pseudorapidity (lab). for Q**2 from 5 to 25 GeV**2.
A new method is employed to measure the neutral current cross section up to Bjorken-x values of one with the ZEUS detector at HERA using an integrated luminosity of 65.1 pb-1 for e+p collisions and 16.7 pb-1 for e-p collisions at sqrt{s}=318 GeV and 38.6 pb-1 for e+p collisions at sqrt{s}=300 GeV. Cross sections have been extracted for Q2 >= 648 GeV2 and are compared to predictions using different parton density functions. For the highest x bins, the data have a tendency to lie above the expectations using recent parton density function parametrizations.
The double differential cross section for the 96-97 E+ P NC scattering data.
The double differential cross section for the 96-97 E+ P NC scattering data.
The double differential cross section for the 96-97 E+ P NC scattering data.
We study the process $e^+e^-\to\pi^+\pi^-\pi^+\pi^-\gamma$, with a hard photon radiated from the initial state. About 60,000 fully reconstructed events have been selected from 89 $fb^{-1}$ of BaBar data. The invariant mass of the hadronic final state defines the effective \epem center-of-mass energy, so that these data can be compared with the corresponding direct $e^+e^-$ measurements. From the $4\pi$-mass spectrum, the cross section for the process $e^+e^-\to\pi^+\pi^-\pi^+\pi^-$ is measured for center-of-mass energies from 0.6 to 4.5 $GeV/c^2$. The uncertainty in the cross section measurement is typically 5%. We also measure the cross sections for the final states $K^+ K^- \pi^+\pi^-$ and $K^+ K^- K^+ K^-$. We observe the $J/\psi$ in all three final states and measure the corresponding branching fractions. We search for X(3872) in $J/\psi (\to\mu^+\mu^-) \pi^+\pi^-$ and obtain an upper limit on the product of the $e^+e^-$ width of the X(3872) and the branching fraction for $X(3872) \to J/\psi\pi^+\pi^-$.
Measured PI+ PI- PI+ PI- cross sections. The errors are statistical only.
Measured K+ K- PI+ PI- cross sections. The errors are statistical only.
Measured K+ K- K+ K- cross sections. The errors are statistical only.
Double-tagged interactions of photons with virtualities Q^2 between 10 GeV^2 and 200 GeV^2 are studied with the data collected by DELPHI at LEPII from 1998 to 2000, corresponding to an integrated luminosity of 550 pb^{-1}. The gam* gam* -> mu+mu- data agree with QED predictions. The cross-section of the reaction gam* gam* -> hadrons is measured and compared to the LO and NLO BFKL calculations.
Measured cross section for the process E+ E- --> E+ E- HADRONS.
Measured cross section for the process GAMMA* GAMMA* --> HADRONS.
Differential cross section for GAMMA* GAMMA* --> MU+ MU-.
The e+e- -> e+e- hadrons reaction, where one of the two electrons is detected in a low polar-angle calorimeter, is analysed in order to measure the hadronic photon structure function F2gamma . The full high-energy and high-luminosity data set, collected with the L3 detector at centre-of-mass energies 189-209GeV, corresponding to an integrated luminosity of 608/pb is used. The Q^2 range 11-34GeV^2 and the x range 0.006-0.556 are considered. The data are compared with recent parton density functions.
Cross sections DELTA(SIG)/DELTA(X) in the Q**2 range 11 TO 14 GeV**2.
Cross sections DELTA(SIG)/DELTA(X) in the Q**2 range 14 TO 20 GeV**2.
Cross sections DELTA(SIG)/DELTA(X) in the Q**2 range 20 TO 34 GeV**2.
The reaction gamma p --> K0 Sigma+ was measured in the photon energy range from threshold up to 2.6 GeV with the SAPHIR detector at the electron stretcher facility, ELSA, in Bonn. Results are presented on the reaction cross section and the polarization of the Sigma+ as a function of the kaon production angle in the centre-of-mass system, cos(Theta_K^{c.m.}), and the photon energy. The cross section is lower and varies less with photon energy and kaon production angle than that of gamma p --> K+ Sigma0. The Sigma+ is polarized predominantly at cos(Theta_K^{c.m.}) \approx 0. The data presented here are more precise than previous ones obtained with SAPHIR and extend the photon energy range to higher values. They are compared to isobar model calculations.
Axis error includes +- 10/10 contribution (Normalization uncertainty already included.).
Axis error includes +- 10/10 contribution (Normalization uncertainty already included.).
Axis error includes +- 10/10 contribution (Normalization uncertainty already included.).
Compton scattering of quasi-real virtual photons, gamma e+- -> gamma e+-, is studied with 0.6fb-1 of data collected by the L3 detector at the LEP e+e- collider at centre-of-mass energies root(s')=189-209GeV. About 4500 events produced by the interaction of virtual photons emitted by e+- of one beam with e-+ of the opposite beam are collected for effective centre-of-mass energies of the photon-electron and photon-positron systems in the range from root(s')= 35GeV up to root(s')=175GeV, the highest energy at which Compton scattering was ever probed. The cross sections of the gamma e+- -> gamma e+- process as a function of root(s') and of the rest-frame scattering angle are measured, combined with previous L3 measurements down to root(s')~20GeV, and found to agree with the QED expectations.
Measured Compton scattering cross section as a function of the effective centre of mass of the photon-electron system. THETA(RF=CM) is the electron rest frame scattering angle.
The measured angular distribution over the photon-electron centre of mass energy range 35 to 175 GeV.
The measured Compton scattering cross section using the full data sample including the lower energy data from Acciarri et al. PL B439(1998)183. Errors are combined statistics and systematics.
Exclusive rho^0 rho^0 production in two-photon collisions between a quasi-real and a mid-virtuality photon is studied with data collected at LEP at centre-of-mass energies 183GeV < sqrt{s} < 209GeV with a total integrated luminosity of 684.8/pb. The cross section of the process gamma gamma* -> rho^0 rho^0 is determined as a function of the photon virtuality, q^2, and the two-photon centre-of-mass energy, Wgg, in the kinematic region: 0.2GeV^2 < q^2 < 0.85GeV^2 and 1.1GeV < Wgg < 3GeV.
Production cross section as a function of Q**2. Differential cross sectionsare corrected to the centre of each bin.
Production cross section for two-photon data as a function of Q**2.
Production cross section as a function of W.
Exclusive rho+rho- production in two-photon collisions between a quasi-real photon, gamma, and a mid-virtuality photon, gamma*, is studied with data collected at LEP at centre-of-mass energies root(s)=183-209GeV with a total integrated luminosity of 684.8pb^-1. The cross section of the gamma gamma* -> rho+ rho- process is determined as a function of the photon virtuality, Q^2, and the two-photon centre-of-mass energy, W_gg, in the kinematic region: 0.2GeV^2 < Q^2 <0.85GeV^2 and 1.1GeV < W_gg < 3GeV. These results, together with previous L3 measurements of rho0 rho0 and rho+ rho- production, allow a study of the gamma gamma* -> rho rho process over the Q^2-region 0.2GeV^2 < Q^2 < 30 GeV^2.
Production cross section as a function of Q**2. Differential cross sectionsare corrected to the centre of each bin.
Production cross section for two-photon data as a function of Q**2.
Production cross section as a function of W.
A high precision study of the process gamma gamma -> p p-bar has been performed using a data sample of 89/fb collected with the Belle detector at the KEKB e+e- collider. The cross section of p p-bar production has been measured at two-photon center-of-mass (c.m.) energies between 2.025 and 4.0 GeV and in the c.m. angular range of |cos(theta^*)|<0.6. Production of gamma gamma -> eta_c -> p p-bar is observed and the product of the two-photon width of the eta_c and its branching ratio to p p-bar is determined.
Measured cross section for GAMMA GAMMA --> PBAR P in the angular region ABS(COS(THETA)) < 0.6.
Measured differential cross sections versus COS(THETA) for the W ranges 2.075 to 2.5, 2.5 to 3.0 and 3.0 to 4.0 GeV.
Measured differential cross sections versus COS(THETA) for the W ranges 2.075 to 2.1, 2.1 to 2.2 and 2.2 to 2.3 GeV.
Deep inelastic scattering and its diffractive component, ep -> e'gamma*p ->e'XN, have been studied at HERA with the ZEUS detector using an integrated luminosity of 4.2 pb-1. The measurement covers a wide range in the gamma*p c.m. energy W (37 - 245 GeV), photon virtuality Q2 (2.2 - 80 GeV2) and mass Mx. The diffractive cross section for Mx > 2 GeV rises strongly with W: the rise is steeper with increasing Q2. The latter observation excludes the description of diffractive deep inelastic scattering in terms of the exchange of a single Pomeron. The ratio of diffractive to total cross section is constant as a function of W, in contradiction to the expectation of Regge phenomenology combined with a naive extension of the optical theorem to gamma*p scattering. Above Mx of 8 GeV, the ratio is flat with Q2, indicating a leading-twist behaviour of the diffractive cross section. The data are also presented in terms of the diffractive structure function, F2D(3)(beta,xpom,Q2), of the proton. For fixed beta, the Q2 dependence of xpom F2D(3) changes with xpom in violation of Regge factorisation. For fixed xpom, xpom F2D(3) rises as beta -> 0, the rise accelerating with increasing Q2. These positive scaling violations suggest substantial contributions of perturbative effects in the diffractive DIS cross section.
Measurement of the proton structure function F2 at Q**2 = 2.7 GeV**2.
Measurement of the proton structure function F2 at Q**2 = 4.0 GeV**2.
Measurement of the proton structure function F2 at Q**2 = 6.0 GeV**2.
The process e+e- --> pi+ pi- pi0 gamma has been studied at a center-of-mass energy near the Y(4S) resonance using a 89.3 fb-1 data sample collected with the BaBar detector at the PEP-II collider. From the measured 3pi mass spectrum we have obtained the products of branching fractions for the omega and phi mesons, B(omega --> e+e-)B(omega --> 3pi)=(6.70 +/- 0.06 +/- 0.27)10-5 and B(phi --> e+e-)B(phi --> 3pi)=(4.30 +/- 0.08 +/- 0.21)10-5, and evaluated the e+e- --> pi+ pi- pi0 cross section for the e+e- center-of-mass energy range 1.05 to 3.00 GeV. About 900 e+e- --> J/psi gamma --> pi+ pi- pi0 gamma events have been selected and the branching fraction B(J/psi --> pi+ pi- pi0)=(2.18 +/- 0.19)% has been measured.
The measured 3PI mass spectrum calculated for a 25 MeV bin size.
Neutral current single pi0 production induced by neutrinos with a mean energy of 1.3 GeV is measured at a 1000 ton water Cherenkov detector as a near detector of the K2K long baseline neutrino experiment. The cross section for this process relative to the total charged current cross section is measured to be 0.064 +- 0.001 (stat.) +- 0.007 (sys.). The momentum distribution of produced pi0s is measured and is found to be in good agreement with an expectation from the present knowledge of the neutrino cross sections.
Ratio of single PI0 NC cross section to the total CC cross section. For reference the total CC cross section is calculated to be 1.1 x 10**-38 CM**2/nucleon averaged over the K2K neutrino beam energy.
Cross sections for e^+p neutral current deep inelastic scattering have been measured at a centre-of-mass energy of sqrt{s}=318 GeV with the ZEUS detector at HERA using an integrated luminosity of 63.2 pb^-1. The double-differential cross section, d^2sigma/dxdQ^2, is presented for 200 GeV^2 < Q^2 < 30000 GeV^2 and for 0.005 < x < 0.65. The single-differential cross-sections dsigma/dQ^2, dsigma/dx and dsigma/dy are presented for Q^2 > 200 GeV^2. The effect of Z-boson exchange is seen in dsigma/dx measured for Q^2 > 10000 GeV^2. The data presented here were combined with ZEUS e^+p neutral current data taken at sqrt{s}=300 GeV and the structure function F_2^{em} was extracted. All results agree well with the predictions of the Standard Model.
The single differential DSIG/DQ**2 cross section corrected to the electroweak Born level. See next table for a breakdown of the systematic errors.
Systematic errors with bin to bin correlations for the cross section DSIG/DQ**2.
Single differential cross section DSIG/DX for a Q**2 cut of 200 GeV**2 corrected to the electroweak Born level.
Deep-inelastic positron-proton interactions at low values of Bjorken-x down to x \approx 4.10^-5 which give rise to high transverse momentum pi^0 mesons are studied with the H1 experiment at HERA. The inclusive cross section for pi^0 mesons produced at small angles with respect to the proton remnant (the forward region) is presented as a function of the transverse momentum and energy of the pi^0 and of the four-momentum transfer Q^2 and Bjorken-x. Measurements are also presented of the transverse energy flow in events containing a forward pi^0 meson. Hadronic final state calculations based on QCD models implementing different parton evolution schemes are confronted with the data.
The inclusive PI0 cross section as a function of the Bjorken X.
The inclusive PI0 cross section as a function of the Bjorken X.
The inclusive PI0 cross section as a function of the Bjorken X.
Using a sample of 3.3 million Upsilon(4S) -> BBbar events collected with the CLEO II detector at the Cornell Electron Storage Ring (CESR), we measure the branching fraction for B -> rho l nu, |V_ub|, and the partial rate (Delta Gamma) in three bins of q^2 = (p_B-p_rho)^2. We find B(B^0 -> rho^- l^+ nu)=(2.69 +- 0.41^+0.35_-0.40 +- 0.50) 10^-4, |V_ub|=(3.23 +- 0.24^+0.23_-0.26 +- 0.58) 10^-3, Delta Gamma (0 < q^2 < 7 GeV^2/c^4) =(7.6 +- 3.0 ^+0.9_-1.2 +- 3.0) 10^-2 ns^-1, Delta Gamma (7 < q^2 < 14 GeV^2/c^4) =(4.8 +- 2.9 ^+0.7_-0.8 +- 0.7) 10^-2 ns^-1, and Delta Gamma (14 < q^2 < 21 GeV^2/c^4) = (7.1 +- 2.1^+0.9_-1.1 +- 0.6)10^-2 ns^-1. The quoted errors are statistical, systematic, and theoretical. The method is sensitive primarily to B -> rho l nu decays with leptons in the energy range above 2.3 GeV. Averaging with the previously published CLEO results, we obtain B(B^0 -> rho^- l^+ nu) = (2.57 +- 0.29^+0.33_-0.46 +- 0.41) 10^-4 and |V_{ub}| = (3.25 +- 0.14 ^+0.21_-0.29 +- 0.55) 10^-3.
VCB is the V-CKM (Cabibbo-Kobayashi-Maskawa) mixing matrix element. LEPTON+- stands for E+- or MU+-.
A new precise measurement of |V_{cb}| and of the branching ratio BR(\bar{B^0} -> D^{*+} \ell^- \bar{\nu_\ell}) has been performed using a sample of about 5000 semileptonic decays \bar{B^0} -> D^{*+} \ell^- \bar{\nu_\ell}, selected by the DELPHI detector at LEP I by tagging the soft pion from D^{*+} -> D^0 \pi^+. The results are: V_{cb}=(39.0 +/- 1.5 (stat.) ^{+2.5}_{-2.6} (syst. exp.) +/- 1.3 (syst. th.)) x 10^{-3} BR(\bar{B^0} -> D^{*+} \ell^- \bar{\nu_\ell})=(4.70 +/- 0.13 (stat.) ^{+0.36}_{-0.31} (syst. exp.))% The analytic dependences of the differential cross-section and of the Isgur Wise form factor as functions of the variable w = v_{B^0}.v_{D^*} have also been obtained by unfolding the experimental resolution.
The formfactors are evaluated at zero recoil of D meson. VCB is the V-CKM (Cabibbo-Kobayashi-Maskawa) mixing matrix element. The value of FORMFACTOR(1) = 0.91 +- 0.03.
We report the branching ratios of the χc2(13P2) and χc0(13P0) charmonium resonances to two photons using event samples collected by Fermilab experiment E835 in the reactions p¯p→χc2(13P2)[χc0(13P0)]. Our result for the χc2 is B(χc2→γγ)=(1.35±0.25±0.12)×10−4. We set a 95% upper limit for the χc0 branching ratio B(χc0→γγ) at 2.09×10−4.
No description provided.
Using a prompt neutrino beam in which a nu_tau component was identified for the first time, the nu_tau magnetic moment was measured based on a search for an anomalous increase in the number of neutrino-electron interactions. One such event was observed when 2.3 were expected from background processes, giving an upper 90% confidence limit of 3.9x10^-7 Bohr magnetons.
CONST(NAME=BOHR MAGNETON) is Bohr magneton.
We measure the relative rate of production of orbitally excited (L=1) states of B mesons (B**) by observing their decays into Bπ±. We reconstruct B mesons through semileptonic decay channels using data collected in pp¯ collisions at s=1.8TeV. The fraction of light B mesons that are produced as L=1B** states is measured to be 0.28±0.06(stat)±0.03(syst). We also measure the collective mass of the B** states, and quantify the result by quoting the (model-dependent) mass of the lowest B** state to be m(B1)=5.71±0.02GeV/c2.
FD is considered as a quark fragmentation fraction.
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.
The Sigma^- mean squared charge radius has been measured in the space-like Q^2 range 0.035-0.105 GeV^2/c^2 by elastic scattering of a Sigma^- beam off atomic electrons. The measurement was performed with the SELEX (E781) spectrometer using the Fermilab hyperon beam at a mean energy of 610 GeV/c. We obtain <r^2> = (0.61 +/- 0.12 (stat.) +/- 0.09 (syst.)) fm^2. The proton and pi^- charge radii were measured as well and are consistent with results of other experiments. Our result agrees with the recently measured strong interaction radius of the Sigma^-.
Total systematic errors are given.
We have measured the probability, n(g->cc~), of a gluon splitting into a charm-quark pair using 1.7 million hadronic Z decays collected by the L3 detector. Two independent methods have been applied to events with a three-jet topology. One method relies on tagging charmed hadrons by identifying a lepton in the lowest energy jet. The other method uses a neural network based on global event shape parameters. Combining both methods, we measure n(g->cc~)= [2.45 +/- 0.29 +/- 0.53]%.
No description provided.
Using data collected with the L3 detector near the Z resonance, corresponding to an integrated luminosity of 150pb-1, the branching fractions of the tau lepton into electron and muon are measured to be B(tau->e nu nu) = (17.806 +- 0.104 (stat.) +- 0.076 (syst.)) %, B(tau->mu nu nu) = (17.342 +- 0.110 (stat.) +- 0.067 (syst.)) %. From these results the ratio of the charged current coupling constants of the muon and the electron is determined to be g_mu/g_e = 1.0007 +- 0.0051. Assuming electron-muon universality, the Fermi constant is measured in tau lepton decays as G_F = (1.1616 +- 0.0058) 10^{-5} GeV^{-2}. Furthermore, the coupling constant of the strong interaction at the tau mass scale is obtained as alpha_s(m_tau^2) = 0.322 +- 0.009 (exp.) +- 0.015 (theory).
First DSYS error is experimental, the second is from theory.
Exclusive production of π and K meson pairs in two photon collisions is measured with ALEPH data collected between 1992 and 2000. Cross-sections are presented as a function of cos θ ∗ and invariant mass, for | cos θ ∗ |<0.6 and invariant masses between 2.0 and 6.0 GeV/ c 2 (2.25 and 4.0 GeV/ c 2 ) for pions (kaons). The shape of the distributions are found to be well described by QCD predictions but the data have a significantly higher normalization.
Measured angular distribution for pion production.
Measured angular distribution for kaon production.
Measured cross section for pion production as a function of W.
Cross sections for the production of two isolated muons up to high di-muon masses are measured in ep collisions at HERA with the H1 detector in a data sample corresponding to an integrated luminosity of 71 pb^-1 at a centre of mass energy of sqrt{s} = 319 GeV. The results are in good agreement with Standard Model predictions, the dominant process being photon-photon interactions. Additional muons or electrons are searched for in events with two high transverse momentum muons using the full data sample corresponding to 114 pb^-1, where data at sqrt{s} = 301 GeV and sqrt{s} = 319 GeV are combined. Both the di-lepton sample and the tri-lepton sample agree well with the predictions.
Integrated cross sections for electroweak muon pair production in the evaluated phase space. The cross section has the di-muon contributions from UPSILON, TAU-PAIR and QUARK-QUARKBAR decay subtracted.
Cross section for the production of two muons in e p interactions as a function of the di-muon mass. This data sample includes di-muons from UPSILON, TAU-PAIR and QUARK-QUARKBAR decays.
Cross section for the production of two muons as a function of the muon transverse momentum (two entries per event).
The hadronic photon structure function $F_2^\gamma(x,Q^2)$ is measured from data taken with the ALEPH detector at LEP. At centre-of-mass energies between
Measured value of F2/ALPHAE at a mean Q**2 of 17.3 GeV**2.
Measured value of F2/ALPHAE at a mean Q**2 of 67.2 GeV**2.
Statistical correlation coefficients for the F2 measurements at Q**2 = 17.3 GeV**2.
K^+K^- production in two-photon collisions has been studied using a large data sample of 67 fb^{-1} accumulated with the Belle detector at the KEKB asymmetric e^+e^- collider. We have measured the cross section for the process gamma gamma -> K^+ K^- for center-of-mass energies between 1.4 and 2.4 GeV, and found three new resonant structures in the energy region between 1.6 and 2.4 GeV. The angular differential cross sections have also been measured.
Cross section for two photon production of K+ K- in the polar angular region ABS(COS(THETA*)) < 0.6.
Differential cross sections DSIG/DCOS(THETA) for the W range 1.40 to 1.56 GeV.. Statistical errors only.
Differential cross sections DSIG/DCOS(THETA) for the W range 1.56 to 1.72 GeV.. Statistical errors only.
Inclusive production of $D^*(2010)$ mesons in deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 81.9 pb$^{-1}$. The decay channel $D^{* +}\to D^0 \pi^+ $ with $D^0\to K^-\pi^+$ and corresponding antiparticle decay were used to identify $D^*$ mesons. Differential $D^*$ cross sections with $1.5<Q^2<1000$ GeV$^2$ and $0.02<y<0.7$ in the kinematic region $1.5<p_T(D^*)<15$ GeV and $|\eta(D^*)|<1.5$ are compared to different QCD calculations incorporating different parameterisations of the parton densities in the proton. The data show sensitivity to the gluon distribution in the proton and are reasonably well described by next-to-leading-order QCD with the ZEUS NLO QCD fit used as the input parton density in the proton. The observed cross section is extrapolated to the full kinematic region in $p_T(D^*)$ and $\eta(D^*)$ in order to determine the open-charm contribution, $F_2^{\rm charm}(x,Q^2)$, to the proton structure function, $F_2$. Since, at low $Q^2$, the uncertainties of the data are comparable to those from the QCD fit, the measured differential cross sections in $y$ and $Q^2$ should be used in future fits to constrain the gluon density.
Overall total cross section. The second DSYS error is due to the uncertainty in the BR for D* and D0 decay.
Measured differential cross section as a function of Q**2.
Measured differential cross section as a function of X.
Cross sections for e^+p charged current deep inelastic scattering at a centre-of-mass energy of 318 GeV have been determined with an integrated luminosity of 60.9pb^-1 collected with the ZEUS detector at HERA. The differential cross sections dsigma/dQ^2, dsigma/dx and dsigma/dy for Q^2>200 GeV^2 are presented. In addition, d^2sigma/dxdQ^2 has been measured in the kinematic range 280 GeV^2 < Q^2 < 17000 GeV^2 and 0.008 < x < 0.42. The predictions of the Standard Model agree well with the measured cross sections. The mass of the W boson propagator is determined to be M_W=78.9 +/- 2.0 (stat.) +/- 1.8 (syst.) +2.0 -1.8 (PDF) GeV from a fit to dsigma/dQ^2. The chiral structure of the Standard Model is also investigated in terms of the (1-y)^2 dependence of the the double-differential cross section. The structure-function F_2^CC has been extracted by combining the measurements presented here with previous ZEUS results from e^-p scattering, extending the measurement obtained in a neutrino-nucleus scattering experiment to a significantly higher Q^2 region.
The total cross section for Q**2 > 200 GeV**2.
The differential cross section as a function of Q**2.
The differential cross section as a function of X.
Forum