In this contribution, Double Parton Scattering processes observed with the ATLAS detector at LHC are discussed. Results of five analyses are presented: production of W boson in association with 2 ...jets, production of J/psi meson in association with W boson, J/psi production with Z boson, J/psi pair production and four jet events.
The photoproduction of isolated photons, both inclusive and together with a jet, has been measured with the ZEUS detector at HERA using an integrated luminosity of 374 pb−1. Differential cross ...sections are presented in the isolated-photon transverse-energy and pseudorapidity ranges 6<ETγ<15 GeV and −0.7<ηγ<0.9, and for jet transverse-energy and pseudorapidity ranges 4<ETjet<35 GeV and −1.5<ηjet<1.8, for exchanged-photon virtualities Q2<1 GeV2. Differential cross sections are also presented for inclusive isolated-photon production as functions of the transverse energy and pseudorapidity of the photon. Higher-order theoretical calculations are compared to the results.
The design and performance of the ZEUS micro vertex detector Polini, A.; Brock, I.; Goers, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2007, Letnik:
581, Številka:
3
Journal Article
Recenzirano
Odprti dostop
In order to extend the tracking acceptance, to improve the primary and secondary vertex reconstruction and thus enhancing the tagging capabilities for short lived particles, the ZEUS experiment at ...the HERA Collider at DESY installed a silicon strip vertex detector. The barrel part of the detector is a 63
cm long cylinder with silicon sensors arranged around an elliptical beampipe. The forward part consists of four circular shaped disks. In total just over 200k channels are read out using
2.9
m
2
of silicon. In this report a detailed overview of the design and construction of the detector is given and the performance of the completed system is reviewed.
A search for a narrow baryonic state in the pKS0 and p‾KS0 system has been performed in ep collisions at HERA with the ZEUS detector using an integrated luminosity of 358pb−1 taken in 2003–2007. The ...search was performed with deep inelastic scattering events at an ep centre-of-mass energy of 318GeV for exchanged photon virtuality, Q2, between 20 and 100GeV2. Contrary to evidence presented for such a state around 1.52 GeV in a previous ZEUS analysis using a sample of 121 pb−1 taken in 1996–2000, no resonance peak was found in the p(p‾)KS0 invariant-mass distribution in the range 1.45–1.7 GeV. Upper limits on the production cross section are set.
The first direct measurements of the longitudinal proton structure function
F
L
(
x
,
Q
2
)
at HERA are reported. The measurements were performed by the H1 and ZEUS collaborations. They are based on ...inclusive deep inelastic
e
+
p
scattering cross sections with a positron beam energy of 27.5 GeV and proton beam energies of 920, 575 and 460 GeV. The
F
L
values agree with higher order QCD calculations based on parton densities obtained using cross section data previously measured at HERA.
The production of the excited charm mesons D1(2420) and D2⁎(2460) in ep collisions has been measured with the ZEUS detector at HERA using an integrated luminosity of 373 pb−1. The masses of the ...neutral and charged states, the widths of the neutral states, and the helicity parameter of D1(2420)0 were determined and compared with other measurements and with theoretical expectations. The measured helicity parameter of the D10 allows for some mixing of S- and D-waves in its decay to D⁎±π∓. The result is also consistent with a pure D-wave decay. Ratios of branching fractions of the two decay modes of the D2⁎(2460)0 and D2⁎(2460)± states were measured and compared with previous measurements. The fractions of charm quarks hadronising into D1 and D2⁎ were measured and are consistent with those obtained in e+e− annihilations.
The production of Z0 bosons in the reaction ep→eZ0p(⁎), where p(⁎) stands for a proton or a low-mass nucleon resonance, has been studied in ep collisions at HERA using the ZEUS detector. The analysis ...is based on a data sample collected between 1996 and 2007, amounting to 496 pb−1 of integrated luminosity. The Z0 was measured in the hadronic decay mode. The elasticity of the events was ensured by a cut on ηmax<3.0, where ηmax is the maximum pseudorapidity of energy deposits in the calorimeter defined with respect to the proton beam direction. A signal was observed at the Z0 mass. The cross section of the reaction ep→eZ0p(⁎) was measured to be σ(ep→eZ0p(⁎))=0.13±0.06(stat.)±0.01(syst.) pb, in agreement with the Standard Model prediction of 0.16 pb. This is the first measurement of Z0 production in ep collisions.
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