(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) A combination is presented of all inclusive deep inelastic cross sections previously published by the H1 and ZEUS ...collaborations at HERA for neutral and charged current ... scattering for zero beam polarisation. The data were taken at proton beam energies of 920, 820, 575 and 460 GeV and an electron beam energy of 27.5 GeV. The data correspond to an integrated luminosity of about 1 fb... and span six orders of magnitude in negative four-momentum-transfer squared, ..., and Bjorken x. The correlations of the systematic uncertainties were evaluated and taken into account for the combination. The combined cross sections were input to QCD analyses at leading order, next-to-leading order and at next-to-next-to-leading order, providing a new set of parton distribution functions, called HERAPDF2.0. In addition to the experimental uncertainties, model and parameterisation uncertainties were assessed for these parton distribution functions. Variants of HERAPDF2.0 with an alternative gluon parameterisation, HERAPDF2.0AG, and using fixed-flavour-number schemes, HERAPDF2.0FF, are presented. The analysis was extended by including HERA data on charm and jet production, resulting in the variant HERAPDF2.0Jets. The inclusion of jet-production cross sections made a simultaneous determination of these parton distributions and the strong coupling constant possible, resulting in ... An extraction of ... and results on electroweak unification and scaling violations are also presented.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Due to the limited field of view (FoV) of Cherenkov telescopes, the time
needed to achieve target sensitivity for surveys of the extragalactic and
Galactic sky is large. To optimize the time spent to ...perform such surveys, a
so-called "divergent mode" of the Cherenkov Telescope Array Observatory (CTAO)
was proposed as an alternative observation strategy to the traditional parallel
pointing. In the divergent mode, each telescope points to a position in the sky
that is slightly offset, in the outward direction, from the original center of
the field of view. This bring the advantage of increasing the total
instantaneous arrays' FoV. From an enlarged field of view also benefits the
search for very-high-energy transient sources, making it possible to cover
large sky regions in follow-up observations, or to quickly cover the
probability sky map in case of Gamma Ray Bursts (GRB), Gravitational Waves
(GW), and other transient events. In this contribution, we present the proposed
implementation of the divergent pointing mode and its first preliminary
performance estimation for the southern CTAO array.
The exclusive photoproduction reaction gamma p arrow right Upsilon ( 1 S ) p has been studied with the ZEUS detector in ep collisions at HERA using an integrated luminosity of 468 pb - 1 . The ...measurement covers the kinematic range 60 < W < 220 GeV and Q 2 < 1 GeV 2 , where W is the photon-proton centre-of-mass energy and Q 2 is the photon virtuality. The exponential slope, b, of the t dependence of the cross section, where t is the squared four-momentum transfer at the proton vertex, has been measured, yielding b = 4.3 - 1.3 + 2.0 ( stat . ) - 0.6 + 0.5 ( syst . ) GeV - 2 . This constitutes the first measurement of the t dependence of the gamma p arrow right Upsilon ( 1 S ) p cross section.
The Cherenkov Telescope Array (CTA) will be the next-generation observatory in the field of very-high-energy (20 GeV to 300 TeV) gamma-ray astroparticle physics. Classically, data analysis in the ...field maximizes sensitivity by applying quality cuts on the data acquired. These cuts, optimized using Monte Carlo simulations, select higher quality events from the initial dataset. Subsequent steps of the analysis typically use the surviving events to calculate one set of instrument response functions (IRFs). An alternative approach is the use of event types, as implemented in experiments such as the Fermi-LAT. In this approach, events are divided into sub-samples based on their reconstruction quality, and a set of IRFs is calculated for each sub-sample. The sub-samples are then combined in a joint analysis, treating them as independent observations. This leads to an improvement in performance parameters such as sensitivity, angular and energy resolution. Data loss is reduced since lower quality events are included in the analysis as well, rather than discarded. In this study, machine learning methods will be used to classify events according to their expected angular reconstruction quality. We will report the impact on CTA high-level performance when applying such an event-type classification, compared to the classical procedure.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Charm production in deep inelastic ep scattering was measured with the ZEUS detector using an integrated luminosity of 354 ...pb^sup -1^. Charm quarks were identified by reconstructing D ^sup ±^ mesons in the D ^sup ±^ arrow right K ^sup ^pi^sup ±^pi^sup ±^ decay channel. Lifetime information was used to reduce combinatorial background substantially. Differential cross sections were measured in the kinematic region 5 < Q ^sup 2^ < 1000 GeV^sup 2^, 0.02 < y < 0.7, 1.5 < p ^sub T^ (D ^sup ±^) < 15 GeV and |eta(D ^sup ±^)| < 1.6, where Q ^sup 2^ is the photon virtuality, y is the inelasticity, and p ^sub T^ (D ^sup ±^) and eta(D ^sup ±^) are the transverse momentum and the pseudorapidity of the D ^sup ±^ meson, respectively. Next-to-leading-order QCD predictions are compared to the data. The charm contribution, ..., to the proton structure-function F ^sub 2^ was extracted.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) The production of D ^sup *±^ mesons in deep inelastic ep scattering has been measured for exchanged photon virtualities 5<Q ...^sup 2^<1000 GeV^sup 2^, using an integrated luminosity of 363 pb^sup -1^ with the ZEUS detector at HERA. Differential cross sections have been measured and compared to next-to-leading-order QCD calculations. The cross-sections are used to extract the charm contribution to the proton structure functions, expressed in terms of the reduced charm cross section, ... Theoretical calculations based on fits to inclusive HERA data are compared to the results.
The cross sections for inelastic photoproduction of J/psi and psi' mesons have been measured in ep collisions with the ZEUS detector at HERA, using an integrated luminosity of 468 pb^sup -1^ ...collected in the period 1996-2007. The psi' to J/psi cross section ratio was measured in the range 0.55<z<0.9 and 60<W<190 GeV as a function of W, z and p ^sub T^. Here W denotes the photon-proton centre-of-mass energy, z is the fraction of the incident photon energy carried by the meson and p ^sub T^ is the transverse momentum of the meson with respect to the beam axis. The J/psi cross sections were measured for 0.1<z<0.9, 60<W<240 GeV and p ^sub T^ >1 GeV. Theoretical predictions within the non-relativistic QCD framework including NLO colour-singlet and colour-octet contributions were compared to the data, as were predictions based on the k ^sub T^-factorisation approach.
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