We present the observation of doubly produced $J / \psi$ mesons as an example of processes containing a substantial fraction of double parton scattering. Measurements of the production cross sections ...for singly and doubly-produced $J/\psi$ mesons were done with the D0 detector at Fermilab in $p\bar{p}$ collisions at $\sqrt{s}$ = 1.96 TeV with an integrated luminosity of 8.1 fb$^{-1}$. For the first time, the double $J / \psi$ production cross section is separated into two parts: contributions from both single and double parton scattering. Lastly, this separation allowed us to determine the effective cross section σeff, a parameter related to the parton spatial density inside the hadron.
A
bstract
The production of
D
0
,
D
*
+
,
D
+
,
and
charm hadrons and their antiparticles in
ep
scattering at HERA has been studied with the ZEUS detector, using a total integrated luminosity of 372 ...pb
−1
. The fractions of charm quarks hadronising into a particular charm hadron were derived. In addition, the ratio of neutral to charged
D
-meson production rates, the fraction of charged
D
mesons produced in a vector state, and the stangeness-suppression factor have been determined. The measurements have been performed in the photoproduction regime. The charm hadrons were reconstructed in the range of transverse momentum
p
T
>
3
.
8 GeV and pseudorapidity |
η
|
<
1
.
6. The charm fragmentation fractions are compared to previous results from HERA and from
e
+
e
−
experiments. The data support the hypothesis that fragmentation is independent of the production process.
We measure the top quark mass in dilepton final states of tt¯ events in pp¯ collisions at s=1.96 TeV, using data corresponding to an integrated luminosity of 9.7 fb−1 at the Fermilab Tevatron ...Collider. The analysis features a comprehensive optimization of the neutrino weighting method to minimize the statistical uncertainties. We also improve the calibration of jet energies using the calibration determined in tt¯→lepton+jets events, which reduces the otherwise limiting systematic uncertainty from the jet energy scale. The measured top quark mass is mt=173.32±1.36(stat)±0.85(syst) GeV.
A search for single-top production, ep→etX, has been performed with the ZEUS detector at HERA using data corresponding to an integrated luminosity of 0.37 fb−1. No evidence for top production was ...found, consistent with the expectation from the Standard Model. Limits were computed for single-top production via flavour changing neutral current transitions involving a neutral electroweak vector boson, γ or Z. The result was combined with a previous ZEUS result yielding a total luminosity of 0.50 fb−1. A 95% credibility level upper limit of 0.13 pb was obtained for the cross section at the centre-of-mass energy of s=315 GeV.
Abstract We report results from a study of B ± → DK ± decays followed by D decaying to the CP-even final state K + K − and CP-odd final state K S 0 π 0 $$ {K}_S^0{\pi}^0 $$ , where D is an admixture ...of D 0 and D ¯ 0 $$ {\overline{D}}^0 $$ states. These decays are sensitive to the Cabibbo-Kobayashi-Maskawa unitarity-triangle angle ϕ 3. The results are based on a combined analysis of the final data set of 772 × 106 B B ¯ $$ B\overline{B} $$ pairs collected by the Belle experiment and a data set of 198 × 106 B B ¯ $$ B\overline{B} $$ pairs collected by the Belle II experiment, both in electron-positron collisions at the Υ(4S) resonance. We measure the CP asymmetries to be A $$ \mathcal{A} $$ CP+ = (+12.5 ± 5.8 ± 1.4)% and A $$ \mathcal{A} $$ CP− = (−16.7 ± 5.7 ± 0.6)%, and the ratios of branching fractions to be R $$ \mathcal{R} $$ CP+ = 1.164 ± 0.081 ± 0.036 and R $$ \mathcal{R} $$ CP− = 1.151 ± 0.074 ± 0.019. The first contribution to the uncertainties is statistical, and the second is systematic. The asymmetries A $$ \mathcal{A} $$ CP+ and A $$ \mathcal{A} $$ CP− have similar magnitudes and opposite signs; their difference corresponds to 3.5 standard deviations. From these values we calculate 68.3% confidence intervals of (8.5 ° < ϕ 3 < 16.5 ° ) or (84.5 ° < ϕ 3 < 95.5 ° ) or (163.3 ° < ϕ 3 < 171.5 ° ) and 0.321 < r B < 0.465.
Single- and double-differential inclusive dijet cross sections in neutral current deep inelastic
ep
scattering have been measured with the ZEUS detector using an integrated luminosity of 374 pb
−1
. ...The measurement was performed at large values of the photon virtuality,
Q
2
, between 125 and 20 000 GeV
2
. The jets were reconstructed with the
k
T
cluster algorithm in the Breit reference frame and selected by requiring their transverse energies in the Breit frame,
, to be larger than 8 GeV. In addition, the invariant mass of the dijet system,
, was required to be greater than 20 GeV. The cross sections are described by the predictions of next-to-leading-order QCD.
Abstract We measure CP asymmetries and branching-fraction ratios for B ± → DK ± and Dπ ± decays with D → K S 0 $$ {K}_{\textrm{S}}^0 $$ K ± π ∓, where D is a superposition of D 0 and D ¯ $$ ...\overline{D} $$ 0. We use the full data set of the Belle experiment, containing 772 × 106 B B ¯ $$ B\overline{B} $$ pairs, and data from the Belle II experiment, containing 387 × 106 B B ¯ $$ B\overline{B} $$ pairs, both collected in electron-positron collisions at the Υ(4S) resonance. Our results provide model-independent information on the unitarity triangle angle ϕ 3.
PDF
