304 research outputs found
Search for a narrow baryonic state decaying to and in deep inelastic scattering at HERA
A search for a narrow baryonic state in the and
system has been performed in collisions at HERA with the ZEUS detector
using an integrated luminosity of 358 pb taken in 2003-2007. The search
was performed with deep inelastic scattering events at an centre-of-mass
energy of 318 GeV for exchanged photon virtuality, , between 20 and 100
. Contrary to evidence presented for such a state around 1.52
GeV in a previous ZEUS analysis using a sample of 121 pb taken in
1996-2000, no resonance peak was found in the invariant-mass
distribution in the range 1.45-1.7 GeV. Upper limits on the production cross
section are set.Comment: 16 pages, 4 figures, accepted by Phys. Lett. B. Minor changes from
journal reviewing process, including a small correction to figure
Combined QCD and electroweak analysis of HERA data
A simultaneous fit of parton distribution functions (PDFs) and electroweak
parameters to HERA data on deep inelastic scattering is presented. The input
data are the neutral current and charged current inclusive cross sections which
were previously used in the QCD analysis leading to the HERAPDF2.0 PDFs. In
addition, the polarisation of the electron beam was taken into account for the
ZEUS data recorded between 2004 and 2007. Results on the vector and
axial-vector couplings of the Z boson to u- and d-type quarks, on the value of
the electroweak mixing angle and the mass of the W boson are presented. The
values obtained for the electroweak parameters are in agreement with Standard
Model predictions.Comment: 32 pages, 10 figures, accepted by Phys. Rev. D. Small corrections
from proofing process and small change to Fig. 12 and Table
Limits on the effective quark radius from inclusive scattering at HERA
The high-precision HERA data allows searches up to TeV scales for Beyond the
Standard Model contributions to electron-quark scattering. Combined
measurements of the inclusive deep inelastic cross sections in neutral and
charged current scattering corresponding to a luminosity of around 1
fb have been used in this analysis. A new approach to the beyond the
Standard Model analysis of the inclusive data is presented; simultaneous
fits of parton distribution functions together with contributions of "new
physics" processes were performed. Results are presented considering a finite
radius of quarks within the quark form-factor model. The resulting 95% C.L.
upper limit on the effective quark radius is cm.Comment: 10 pages, 4 figures, accepted by Phys. Lett.
Measurement of the cross-section ratio sigma_{psi(2S)}/sigma_{J/psi(1S)} in deep inelastic exclusive ep scattering at HERA
The exclusive deep inelastic electroproduction of and
at an centre-of-mass energy of 317 GeV has been studied with the ZEUS
detector at HERA in the kinematic range GeV,
GeV and GeV, where is the photon virtuality, is the
photon-proton centre-of-mass energy and is the squared four-momentum
transfer at the proton vertex. The data for GeV were taken in
the HERA I running period and correspond to an integrated luminosity of 114
pb. The data for GeV are from both HERA I and HERA II
periods and correspond to an integrated luminosity of 468 pb. The decay
modes analysed were and for the
and for the . The cross-section ratio
has been measured as a function of
and . The results are compared to predictions of QCD-inspired
models of exclusive vector-meson production.Comment: 24 pages, 8 figure
Measurement of neutral current e+/-p cross sections at high Bjorken x with the ZEUS detector
The neutral current e+/-p cross section has been measured up to values of
Bjorken x of approximately 1 with the ZEUS detector at HERA using an integrated
luminosity of 187 inv. pb of e-p and 142 inv. pb of e+p collisions at sqrt(s) =
318GeV. Differential cross sections in x and Q2, the exchanged boson
virtuality, are presented for Q2 geq 725GeV2. An improved reconstruction method
and greatly increased amount of data allows a finer binning in the high-x
region of the neutral current cross section and leads to a measurement with
much improved precision compared to a similar earlier analysis. The
measurements are compared to Standard Model expectations based on a variety of
recent parton distribution functions.Comment: 39 pages, 9 figure
Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR
Substantial experimental and theoretical efforts worldwide are devoted to
explore the phase diagram of strongly interacting matter. At LHC and top RHIC
energies, QCD matter is studied at very high temperatures and nearly vanishing
net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was
created at experiments at RHIC and LHC. The transition from the QGP back to the
hadron gas is found to be a smooth cross over. For larger net-baryon densities
and lower temperatures, it is expected that the QCD phase diagram exhibits a
rich structure, such as a first-order phase transition between hadronic and
partonic matter which terminates in a critical point, or exotic phases like
quarkyonic matter. The discovery of these landmarks would be a breakthrough in
our understanding of the strong interaction and is therefore in the focus of
various high-energy heavy-ion research programs. The Compressed Baryonic Matter
(CBM) experiment at FAIR will play a unique role in the exploration of the QCD
phase diagram in the region of high net-baryon densities, because it is
designed to run at unprecedented interaction rates. High-rate operation is the
key prerequisite for high-precision measurements of multi-differential
observables and of rare diagnostic probes which are sensitive to the dense
phase of the nuclear fireball. The goal of the CBM experiment at SIS100
(sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD
matter: the phase structure at large baryon-chemical potentials (mu_B > 500
MeV), effects of chiral symmetry, and the equation-of-state at high density as
it is expected to occur in the core of neutron stars. In this article, we
review the motivation for and the physics programme of CBM, including
activities before the start of data taking in 2022, in the context of the
worldwide efforts to explore high-density QCD matter.Comment: 15 pages, 11 figures. Published in European Physical Journal
Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF
The Physics Program for the Deep Underground Neutrino Experiment (DUNE) at
the Fermilab Long-Baseline Neutrino Facility (LBNF) is described
Химический состав атмосферного аэрозоля арктических районов в летний период 2021 года
Atmospheric aerosol is an important characteristic of the state of the atmospheric air, therefore, in the summer of 2021, atmospheric aerosol samples were collected in the expeditions of the Shirshov Institute of Oceanology of the Russian Academy of Sciences to study the chemical composition (ions, trace elements, polyaromatic hydrocarbons) of aerosols in the Arctic atmosphere. The expeditions were carried out on the research ship (RS) Akademik Mstislav Keldysh in the Kara Sea (83rd cruise, June 18 - July 8, 2021), in the Barents Sea and the Norwegian-Greenland Basin (84th cruise, July 24 - August 26, 2021). It is established that the average total concentration of ions in the aerosol of the Kara Sea is 5.4±1.9 µg/m3, which corresponds to the average data obtained in previous years. In the aerosol of the Barents Sea and the Norwegian-Greenland basin, the average value of 5.0±2.1 μg/m3 was considered as potentially possible for the studied region. Concentrations of such ions as Na+, NH4 + and Cl-dominated in the aerosol composition of all regions. The average total concentration of trace elements in the composition of the aerosol of the Barents Sea and the Norwegian-Greenland basin is 1,5 times higher than in the aerosol of the Kara Sea. The predominant concentrations of trace elements in the aerosol of both study areas were Cr, Zn, Al, Fe. Mo, Sr, Ba, Mn, Sn, Ti, Pb, Cu, Ni. As a result of the calculation of the ranking of trace elements by atmospheric pollution in the aerosol of the Kara Sea, Fe, Cu, Ni, Pb are prioritized, and in the aerosol of the Barents Sea and the Norwegian-Greenland basin - Fe, Cu, Sn, Pb. The level of air pollution with trace elements in both areas is low. 13 compounds of polyaromatic hydrocarbons with an average total concentration of 0.65 ng/m3 in aerosol collected in 83 cruise, and 0.75 ng/m3 in 84 one were identified. Compounds of polyaromatic hydrocarbons with two and three benzene rings (naphthalene, phenanthrene and their homologues) coming from petrogenic sources accounted for 92 and 80% of the total amount of polyaromatic hydrocarbons, respectively. Atmospheric aerosol sampling for the study of chemical composition was carried out under conditions of fog of various densities, with precipitation and destruction of seasonal ice.Выявлены различия и сходство химического состава (ионы, микроэлементы, ПАУ) приводного атмосферного аэрозоля, собранного в летний период 2021 г. по маршрутам экспедиций НИС«Академик Мстислав Келдыш» в районе Карского моря (второй этап 83-го рейса, 18 июня - 8 июля 2021 г.), в Баренцевом море и Норвежско-Гренландском бассейне (84-й рейс, 24 июля - 26 августа 2021 г.)
Measurement of the cross-section ratio in exclusive photoproduction at HERA
The exclusive photoproduction reactions and
have been measured at an centre-of-mass energy
of 318 GeV with the ZEUS detector at HERA using an integrated luminosity of 373
pb. The measurement was made in the kinematic range GeV,
GeV and GeV, where is the photon--proton
centre-of-mass energy, is the photon virtuality and is the squared
four-momentum transfer at the proton vertex. The decay channels used were
, and with subsequent decay . The
ratio of the production cross sections, , has been measured as a function of and and
compared to previous data in photoproduction and deep inelastic scattering and
with predictions of QCD-inspired models of exclusive vector-meson production,
which are in reasonable agreement with the data.Comment: 31 pages, 9 figures. Updated according to comments from journal
referee including a new table. Added full collaboration author lis
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