106 research outputs found
Estimation of Hydrodynamical Model Parameters from the Invariant Spectrum and the Bose-Einstein Correlations of pi-mesons Produced in (pi+/K+)p Interactions at 250 GeV/c
The invariant spectra of pi- mesons produced in (pi+/K+)p interactions at 250
GeV/c are analysed in the framework of the hydrodynamical model of
three-dimensionally expanding cylindrically symmetric finite systems.
A satisfactory description of experimental data is achieved.
The data favour the pattern according to which the hadron matter undergoes
predominantly longitudinal expansion and non-relativistic transverse expansion
with mean transverse velocity = 0.20(7), and is characterized by a large
temperature inhomogeneity in the transverse direction: the extracted freeze-out
temperature at the center of the tube and at the transverse rms radius are
140(3) MeV and 82(7) MeV, respectively. The width of the (longitudinal)
space-time rapidity distribution of the pion source is found to be Delta eta =
1.36(2).
Combining this estimate with results of the Bose-Einstein correlation
analysis in the same experiment, one extracts a mean freeze-out time of the
source of = 1.4(1) fm/c and its transverse geometrical rms radius, R_G
(rms)=1.2(2) fm.Comment: latex, 14 pages, 5 figure
Boost Invariance and Multiplicity Dependence of the Charge Balance Functionin and Collisions at GeV/c
Boost invariance and multiplicity dependence of the charge balance function
are studied in \pi^{+}\rp and \rK^{+}\rp collisions at 250 GeV/ incident
beam momentum. Charge balance, as well as charge fluctuations, are found to be
boost invariant over the whole rapidity region, but both depend on the size of
the rapidity window. It is also found that the balance function becomes
narrower with increasing multiplicity, consistent with the narrowing of the
balance function when centrality and/or system size increase, as observed in
current relativistic heavy ion experiments.Comment: 4 pages, 5 figures, Revte
Entropy Analysis in \pi^{+}\rp and \rK^{+}\rp Collisions at GeV
The entropy properties are analyzed by Ma's coincidence method in
\pi^{+}\rp and \rK^{+}\rp collisions of the NA22 experiment at 250 GeV/
incident momentum. By using the R\'{e}nyi entropies, we test the scaling law
and additivity properties in rapidity space. The behavior of the R\'{e}nyi
entropies as a function of the average number of particles is investigated. The
results are compared with those from the {\sc Pythia} Monte Carlo event
generator.Comment: LaTeX, 11 pages, 5 figure to be appeared in Acta Phys. Pol.
Estimation of hydrodynamical model parameters from the invariant spectrum and the Bose-Einstein correlations of -mesons produced in ( interactions at 250 GeV/c
The invariant spectra of pi- mesons produced in (pi+/K+)p interactions at 250 GeV/c are analysed in the framework of the hydrodynamical model of three-dimensionally expanding cylindrically symmetric finite systems. A satisfactory description of experimental data is achieved. The data favour the pattern according to which the hadron matter undergoes predominantly longitudinal expansion and non-relativistic transverse expansion with mean transverse velocity = 0.20(7), and is characterized by a large temperature inhomogeneity in the transverse direction: the extracted freeze-out temperature at the center of the tube and at the transverse rms radius are 140(3) MeV and 82(7) MeV, respectively. The width of the (longitudinal) space-time rapidity distribution of the pion source is found to be Delta eta = 1.36(2). Combining this estimate with results of the Bose-Einstein correlation analysis in the same experiment, one extracts a mean freeze-out time of the source of = 1.4(1) fm/c and its transverse geometrical rms radius, R_G (rms)=1.2(2) fm.The invariant spectra of pi- mesons produced in (pi+/K+)p interactions at 250 GeV/c are analysed in the framework of the hydrodynamical model of three-dimensionally expanding cylindrically symmetric finite systems. A satisfactory description of experimental data is achieved. The data favour the pattern according to which the hadron matter undergoes predominantly longitudinal expansion and non-relativistic transverse expansion with mean transverse velocity = 0.20(7), and is characterized by a large temperature inhomogeneity in the transverse direction: the extracted freeze-out temperature at the center of the tube and at the transverse rms radius are 140(3) MeV and 82(7) MeV, respectively. The width of the (longitudinal) space-time rapidity distribution of the pion source is found to be Delta eta = 1.36(2). Combining this estimate with results of the Bose-Einstein correlation analysis in the same experiment, one extracts a mean freeze-out time of the source of = 1.4(1) fm/c and its transverse geometrical rms radius, R_G (rms)=1.2(2) fm
Self-affine scaling from non-integer phase-space partition in and collisions at 250 GeV/
A factorial-moment analysis with real (integer and non-integer) phase space partition is applied to p and Kp collisions at 250 GeV/. Clear evidence is shown for self-affine rather than self-similar power-law scaling in multiparticle production. The three-dimensional self-affine second-order scaling exponent is determined to be 0.0610.010.A factorial-moment analysis with real (integer and non-integer) phase space partition is applied to p and Kp collisions at 250 GeV/. Clear evidence is shown for self-affine rather than self-similar power-law scaling in multiparticle production. The three-dimensional self-affine second-order scaling exponent is determined to be 0.0610.010.A factorial-moment analysis with real (integer and non-integer) phase space partition is applied to p and Kp collisions at 250 GeV/. Clear evidence is shown for self-affine rather than self-similar power-law scaling in multiparticle production. The three-dimensional self-affine second-order scaling exponent is determined to be 0.0610.010.A factorial-moment analysis with real (integer and non-integer) phase space partition is applied to π + p and K + p collisions at 250 GeV/ c . Clear evidence is shown for self-affine rather than self-similar power-law scaling in multiparticle production. The three-dimensional self-affine second-order scaling exponent is determined to be 0.061±0.010
Large Self-affine fractality in \p^+p and Kp collisions at 250 GeV/
Taking into account the anisotropy of phase space in multiparticle
production, a self-affine analysis of factorial moments was carried out on the
NA22 data for \p^+\Pp and \PK^+\Pp collisions at 250 GeV/. Within the
transverse plane, the Hurst exponents measuring the anisotropy are consistent
with unit value (i.e. no anisotropy). They are, however, only half that value
when the longitudinal direction is compared to the transverse ones. Fractality,
indeed, turns out to be self-affine rather than self-similar in multiparticle
production. In three-dimensional phase space, power-law scaling is observed to
be better realized in self-affine than in self-similar analysis.Comment: 10 pages and 4 figure
Measurement of (anti)deuteron and (anti)proton production in DIS at HERA
The first observation of (anti)deuterons in deep inelastic scattering at HERA
has been made with the ZEUS detector at a centre-of-mass energy of 300--318 GeV
using an integrated luminosity of 120 pb-1. The measurement was performed in
the central rapidity region for transverse momentum per unit of mass in the
range 0.3<p_T/M<0.7. The particle rates have been extracted and interpreted in
terms of the coalescence model. The (anti)deuteron production yield is smaller
than the (anti)proton yield by approximately three orders of magnitude,
consistent with the world measurements.Comment: 26 pages, 9 figures, 5 tables, submitted to Nucl. Phys.
Forward jet production in deep inelastic ep scattering and low-x parton dynamics at HERA
Differential inclusive jet cross sections in neutral current deep inelastic
ep scattering have been measured with the ZEUS detector. Three phase-space
regions have been selected in order to study parton dynamics where the effects
of BFKL evolution might be present. The measurements have been compared to the
predictions of leading-logarithm parton shower Monte Carlo models and
fixed-order perturbative QCD calculations. In the forward region, QCD
calculations at order alpha_s^1 underestimate the data up to an order of
magnitude at low x. An improved description of the data in this region is
obtained by including QCD corrections at order alpha_s^2, which account for the
lowest-order t-channel gluon-exchange diagrams, highlighting the importance of
such terms in parton dynamics at low x.Comment: 25 pages, 4 figure
Search for lepton-flavor violation at HERA
A search for lepton-flavor-violating interactions and has been performed with the ZEUS detector using the entire HERA I
data sample, corresponding to an integrated luminosity of 130 pb^{-1}. The data
were taken at center-of-mass energies, , of 300 and 318 GeV. No
evidence of lepton-flavor violation was found, and constraints were derived on
leptoquarks (LQs) that could mediate such interactions. For LQ masses below
, limits were set on , where
is the coupling of the LQ to an electron and a
first-generation quark , and is the branching ratio of
the LQ to the final-state lepton ( or ) and a quark . For
LQ masses much larger than , limits were set on the four-fermion
interaction term for LQs that couple to an electron and a quark
and to a lepton and a quark , where and are
quark generation indices. Some of the limits are also applicable to
lepton-flavor-violating processes mediated by squarks in -Parity-violating
supersymmetric models. In some cases, especially when a higher-generation quark
is involved and for the process , the ZEUS limits are the most
stringent to date.Comment: 37 pages, 10 figures, Accepted by EPJC. References and 1 figure (Fig.
6) adde
Multijet production in neutral current deep inelastic scattering at HERA and determination of alpha_s
Multijet production rates in neutral current deep inelastic scattering have
been measured in the range of exchanged boson virtualities 10 < Q2 < 5000 GeV2.
The data were taken at the ep collider HERA with centre-of-mass energy sqrt(s)
= 318 GeV using the ZEUS detector and correspond to an integrated luminosity of
82.2 pb-1. Jets were identified in the Breit frame using the k_T cluster
algorithm in the longitudinally invariant inclusive mode. Measurements of
differential dijet and trijet cross sections are presented as functions of jet
transverse energy E_{T,B}{jet}, pseudorapidity eta_{LAB}{jet} and Q2 with
E_{T,B}{jet} > 5 GeV and -1 < eta_{LAB}{jet} < 2.5. Next-to-leading-order QCD
calculations describe the data well. The value of the strong coupling constant
alpha_s(M_Z), determined from the ratio of the trijet to dijet cross sections,
is alpha_s(M_Z) = 0.1179 pm 0.0013(stat.) {+0.0028}_{-0.0046}(exp.)
{+0.0064}_{-0.0046}(th.)Comment: 22 pages, 5 figure
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