The proposals had been considered for development an analytical engineering methodology for the preliminary assessment of the impact of the space debris (SD) value object charge on the dynamics of ...its descent from orbit. The Earth's magnetic field is taken as a dipole, and the charge of SD is taken as a point charge. The orbital motion of the SD is approximated by the Archimedes spiral, the choice of its parameter (spiral step) provides a close approximation to the orbital motion of the SD. The use of the proposed analytical engineering methodology allows to make reasonable design decisions on the control system and charge formation on the SD at the early stages of designing systems propellantless deorbiting. The results have a methodological nature and are intended to provide preliminary estimates.
A
bstract
Two-particle azimuthal correlations have been measured in neutral current deep inelastic
ep
scattering with virtuality
Q
2
>
5 GeV
2
at a centre-of-mass energy
s
= 318 GeV recorded with the ...ZEUS detector at HERA. The correlations of charged particles have been measured in the range of laboratory pseudorapidity
−
1
.
5
< η <
2
.
0 and transverse momentum 0
.
1
< p
T
<
5
.
0 GeV and event multiplicities
N
ch
up to six times larger than the average 〈
N
ch
〉 ≈ 5. The two-particle correlations have been measured in terms of the angular observables
c
n
{2}
= 〈〈
cosn
Δ
φ
〉〉, where
n
is between 1 and 4 and ∆
φ
is the relative azimuthal angle between the two particles. Comparisons with available models of deep inelastic scattering, which are tuned to reproduce inclusive particle production, suggest that the measured two-particle correlations are dominated by contributions from multijet production. The correlations observed here do not indicate the kind of collective behaviour recently observed at the highest RHIC and LHC energies in high-multiplicity hadronic collisions.
A
bstract
Collective behaviour of final-state hadrons, and multiparton interactions are studied in high-multiplicity
ep
scattering at a centre-of-mass energy
s
= 318 GeV with the ZEUS detector at ...HERA. Two- and four-particle azimuthal correlations, as well as multiplicity, transverse momentum, and pseudorapidity distributions for charged-particle multiplicities
N
ch
≥ 20 are measured. The dependence of two-particle correlations on the virtuality of the exchanged photon shows a clear transition from photoproduction to neutral current deep inelastic scattering. For the multiplicities studied, neither the measurements in photoproduction processes nor those in neutral current deep inelastic scattering indicate significant collective behaviour of the kind observed in high-multiplicity hadronic collisions at RHIC and the LHC. Comparisons of PYTHIA predictions with the measurements in photoproduction strongly indicate the presence of multiparton interactions from hadronic fluctuations of the exchanged photon.
.
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 (
s
N
N
=
2.7--4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (
μ
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 2024, in the context of the worldwide efforts to explore high-density QCD matter.
Measurements of open charm and beauty production cross sections in deep inelastic
ep
scattering at HERA from the H1 and ZEUS Collaborations are combined. Reduced cross sections are obtained in the ...kinematic range of negative four-momentum transfer squared of the photon
2.5
GeV
2
≤
Q
2
≤
2000
GeV
2
and Bjorken scaling variable
3
·
10
-
5
≤
x
Bj
≤
5
·
10
-
2
. The combination method accounts for the correlations of the statistical and systematic uncertainties among the different datasets. Perturbative QCD calculations are compared to the combined data. A next-to-leading order QCD analysis is performed using these data together with the combined inclusive deep inelastic scattering cross sections from HERA. The running charm- and beauty-quark masses are determined as
m
c
(
m
c
)
=
1
.
290
-
0.041
+
0.046
(
exp
/
fit
)
-
0.014
+
0.062
(
model
)
-
0.031
+
0.003
(
parameterisation
)
GeV and
m
b
(
m
b
)
=
4
.
049
-
0.109
+
0.104
(
exp
/
fit
)
-
0.032
+
0.090
(
model
)
-
0.031
+
0.001
(
parameterisation
)
GeV
.
The differential cross sections of γ-rays from the
nat
Fe(n,
x
γ) and
209
Bi(n,
x
γ) reactions with a neutron energy of 14.1 MeV are unfolded from amplitude spectra using the regularization ...procedure. The cross section errors are estimated. The experimental results are compared with the theoretical ones obtained within the Hauser-Feshbach statistical model. The sensitivity of the theoretically calculated γ-spectra to characteristics of the excited nuclear states is analyzed.
The HERAPDF2.0 ensemble of parton distribution functions (PDFs) was introduced in 2015. The final stage is presented, a next-to-next-to-leading-order (NNLO) analysis of the HERA data on inclusive ...deep inelastic
ep
scattering together with jet data as published by the H1 and ZEUS collaborations. A perturbative QCD fit, simultaneously of
α
s
(
M
Z
2
)
and the PDFs, was performed with the result
α
s
(
M
Z
2
)
=
0.1156
±
0.0011
(
exp
)
-
0.0002
+
0.0001
(
model
+
parameterisation
)
±
0.0029
(
scale
)
. The PDF sets of HERAPDF2.0Jets NNLO were determined with separate fits using two fixed values of
α
s
(
M
Z
2
)
,
α
s
(
M
Z
2
)
=
0.1155
and 0.118, since the latter value was already chosen for the published HERAPDF2.0 NNLO analysis based on HERA inclusive DIS data only. The different sets of PDFs are presented, evaluated and compared. The consistency of the PDFs determined with and without the jet data demonstrates the consistency of HERA inclusive and jet-production cross-section data. The inclusion of the jet data reduced the uncertainty on the gluon PDF. Predictions based on the PDFs of HERAPDF2.0Jets NNLO give an excellent description of the jet-production data used as input.
A new measurement of inclusive-jet cross sections in the Breit frame in neutral current deep inelastic scattering using the ZEUS detector at the HERA collider is presented. The data were taken in the ...years 2004–2007 at a centre-of-mass energy of
318
GeV
and correspond to an integrated luminosity of
347
pb
-
1
. The jets were reconstructed using the
k
t
-algorithm in the Breit reference frame. They have been measured as a function of the squared momentum transfer,
Q
2
, and the transverse momentum of the jets in the Breit frame,
p
⊥
,
Breit
. The measured jet cross sections are compared to previous measurements and to perturbative QCD predictions. The measurement has been used in a next-to-next-to-leading-order QCD analysis to perform a simultaneous determination of parton distribution functions of the proton and the strong coupling, resulting in a value of
α
s
(
M
Z
2
)
=
0.1142
±
0.0017
(experimental/fit)
-
0.0007
+
0.0006
(model/parameterisation)
-
0.0004
+
0.0006
(scale)
, whose accuracy is improved compared to similar measurements. In addition, the running of the strong coupling is demonstrated using data obtained at different scales.
Abstract The exclusive photoproduction reactions γp → J/ψ(1S)p and γp → ψ(2S)p have been measured at an ep centre-of-mass energy of 318 GeV with the ZEUS detector at HERA using an integrated ...luminosity of 373 pb −1. The measurement was made in the kinematic range 30 < W < 180 GeV, Q 2 < 1 GeV2 and |t| < 1 GeV2, where W is the photon-proton centre-of-mass energy, Q 2 is the photon virtuality and t is the squared four-momentum transfer at the proton vertex. The decay channels used were J/ψ(1S) → μ + μ − , ψ(2S) → μ + μ − and ψ(2S) → J/ψ(1S)π + π − with subsequent decay J/ψ(1S) → μ + μ − . The ratio of the production cross sections, R = σ ψ(2S) /σ J/ψ(1S), has been measured as a function of W and |t| 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.
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