The NA61/SHINE experiment at the CERN Super Proton Synchrotron studies the onset of deconfinement in strongly interacting matter through a beam energy scan of particle production in collisions of ...nuclei of varied sizes. This paper presents results on inclusive double-differential spectra, transverse momentum and rapidity distributions and mean multiplicities of π±, K±, p and $\bar{ρ}$ produced in 40Ar + 45Sc collisions at beam momenta of 13A, 19A, 30A, 40A, 75A and 150A Ge V/c. The analysis uses the 10% most central collisions, where the observed forward energy defines centrality. The energy dependence of the K±/π+ ratios as well as of inverse slope parameters of the K± transverse mass distributions are placed in between those found in inelastic ρ + ρ and central Pb + Pb collisions. The results obtained here establish a system-size dependence of hadron production properties that so far cannot be explained either within statistical or dynamical models.
Abstract The NA61/SHINE experiment at the CERN Super Proton Synchrotron studies the onset of deconfinement in strongly interacting matter through a beam energy scan of particle production in ...collisions of nuclei of varied sizes. This paper presents results on inclusive double-differential spectra, transverse momentum and rapidity distributions and mean multiplicities of $$\pi ^\pm $$ π ± , $$K^\pm $$ K ± , p and $$\bar{p}$$ p ¯ produced in $$^{40}\hbox {Ar+}^{45}\hbox {Sc}$$ 40 Ar+ 45 Sc collisions at beam momenta of 13 A , 19 A , 30 A , 40 A , 75 A and 150 A $$\text{ Ge }\hspace{-1.00006pt}\text{ V }\!/\!c$$ Ge V / c . The analysis uses the 10% most central collisions, where the observed forward energy defines centrality. The energy dependence of the $$K^\pm $$ K ± / $$\pi ^\pm $$ π ± ratios as well as of inverse slope parameters of the $$K^\pm $$ K ± transverse mass distributions are placed in between those found in inelastic $$p+p$$ p + p and central Pb + Pb collisions. The results obtained here establish a system-size dependence of hadron production properties that so far cannot be explained either within statistical or dynamical models.
The BRAHMS collaboration has measured transverse momentum spectra of pions, kaons, protons, and antiprotons at rapidities 0 and 3 for Cu+Cu collisions at s NN =200 GeV. As the collisions become more ...central the collective radial flow increases while the temperature of kinetic freeze-out decreases. The temperature is lower and the radial flow weaker at forward rapidity. Pion and kaon yields with transverse momenta between 1.5 and 2.5 GeV/c are suppressed for central collisions relative to scaled p + p collisions. This suppression, which increases as the collisions become more central, is consistent with jet quenching models and is also present with comparable magnitude at forward rapidity. At such rapidities, initial state effects may also be present and persistence of the meson suppression to high rapidity may reflect a combination of jet quenching and nuclear shadowing. In conclusion, the ratio of protons to mesons increases as the collisions become more central and is largest at forward rapidities.
Gluon shadowing in the Glauber–Gribov model Tywoniuk, K.; Arsene, I.C.; Bravina, L. ...
European physical journal. C, Particles and fields,
01/2007, Letnik:
49, Številka:
1
Journal Article
Recenzirano
Odprti dostop
New data from the HERA experiment on (diffractive) deep inelastic scattering have been used to parameterize the nucleon and pomeron structure functions. Within the Glauber–Gribov model, the ...parameterizations were employed to calculate gluon shadowing for various heavy ions. We compare our results to predictions from other models. Calculations for d+Au collisions at forward rapidities at ultra-relativistic energies have been made and are compared to RHIC data on the nuclear modification factor. The results for gluon shadowing are also confronted with recent data on the nuclear modification factor at =17.3 GeV at various values of the Feynman variable xF, and the energy dependence of the effect is discussed.
The critical point of dense, strongly interacting matter is searched for at the CERN SPS in ^{40}$Ar + ^{45}$Sc collisions at 150A GeV/c. The dependence of second-order scaled factorial moments of ...proton multiplicity distribution on the number of subdivisions of transverse momentum space is measured. The intermittency analysis is performed using both transverse momentum and cumulative transverse momentum. For the first time, statistically independent data sets are used for each subdivision number. The obtained results do not indicate any statistically significant intermittency pattern. An upper limit on the fraction of critical proton pairs and the power of the correlation function is obtained based on a comparison with the Power-law Model developed for this purpose.
The first measurement of the production of pions, kaons, (anti-)protons and ϕ mesons at midrapidity in Xe–Xe collisions at $\sqrt{s_{NN}}$ = 5.44 TeV is presented. Transverse momentum ...(pT) spectra and pT-integrated yields are extracted in several centrality intervals bridging from p–Pb to mid-central Pb–Pb collisions in terms of final-state multiplicity. The study of Xe–Xe and Pb–Pb collisions allows systems at similar charged-particle multiplicities but with different initial geometrical eccentricities to be investigated. A detailed comparison of the spectral shapes in the two systems reveals an opposite behaviour for radial and elliptic flow. In particular, this study shows that the radial flow does not depend on the colliding system when compared at similar charged-particle multiplicity. In terms of hadron chemistry, the previously observed smooth evolution of particle ratios with multiplicity from small to large collision systems is also found to hold in Xe–Xe. In addition, our results confirm that two remarkable features of particle production at LHC energies are also valid in the collision of medium-sized nuclei: the lower proton-to-pion ratio with respect to the thermal model expectations and the increase of the ϕ-to-pion ratio with increasing final-state multiplicity.
Recently, strain engineering has been shown to be a powerful and flexible means of tailoring the properties of ABO3 perovskite thin films. The effect of epitaxial strain on the structure of the ...perovskite unit cell can induce a host of interesting effects, these arising from either polar cation shifts or rotation of the oxygen octahedra, or both. In the multi-ferroic perovskite bismuth ferrite (BiFeO3-BFO), both degrees of freedom exist, and thus a complex behaviour may be expected as one plays with epitaxial strain. In this paper, we review our results on the role of strain on the ferroic transition temperatures and ferroic order parameters. We find that, while the Néel temperature is almost unchanged by strain, the ferroelectric Curie temperature strongly decreases as strain increases in both the tensile and compressive ranges. Also unexpected is the very weak influence of strain on the ferroelectric polarization value. Using effective Hamiltonian calculations, we show that these peculiar behaviours arise from the competition between antiferrodistortive and polar instabilities. Finally, we present results on the magnetic order: while the cycloidal spin modulation present in the bulk survives in weakly strained films, it is destroyed at large strain and replaced by pseudo-collinear antiferromagnetic ordering. We discuss the origin of this effect and give perspectives for devices based on strain-engineered BiFeO3.
Multiferroics are compounds that show ferroelectricity and magnetism. BiFeO 3, by far the most studied, has outstanding ferroelectric properties, a cycloidal magnetic order in the bulk, and many ...unexpected virtues such as conductive domain walls or a low bandgap of interest for photovoltaics. Although this flurry of properties makes BiFeO 3 a paradigmatic multifunctional material, most are related to its ferroelectric character, and its other ferroic property - antiferromagnetism - has not been investigated extensively, especially in thin films. Here we bring insight into the rich spin physics of BiFeO 3 in a detailed study of the static and dynamic magnetic response of strain-engineered films. Using Mössbauer and Raman spectroscopies combined with Landau-Ginzburg theory and effective Hamiltonian calculations, we show that the bulk-like cycloidal spin modulation that exists at low compressive strain is driven towards pseudo-collinear antiferromagnetism at high strain, both tensile and compressive. For moderate tensile strain we also predict and observe indications of a new cycloid. Accordingly, we find that the magnonic response is entirely modified, with low-energy magnon modes being suppressed as strain increases. Finally, we reveal that strain progressively drives the average spin angle from in-plane to out-of-plane, a property we use to tune the exchange bias and giant-magnetoresistive response of spin valves. \textcopyright 2013 Macmillan Publishers Limited. All rights reserved.
Measurements of
K
∗
(
892
)
0
resonance production via its
K
+
π
-
decay mode in inelastic
p+p
collisions at beam momenta 40 and 80
GeV
/
c
(
s
NN
=
8.8
and 12.3
GeV
) are presented. The data were ...recorded by the NA61/SHINE hadron spectrometer at the CERN Super Proton Synchrotron. The
template
method was used to extract the
K
∗
(
892
)
0
signal. Transverse momentum and rapidity spectra were obtained. The mean multiplicities of
K
∗
(
892
)
0
mesons were found to be
(
35.1
±
1.3
(
stat
)
±
3.6
(
sys
)
)
·
10
-
3
at 40
GeV
/
c
and
(
58.3
±
1.9
(
stat
)
±
4.9
(
sys
)
)
·
10
-
3
at 80
GeV
/
c
. The NA61/SHINE results are compared with the
Epos1.99
and Hadron Resonance Gas models as well as with world data. The transverse mass spectra of
K
∗
(
892
)
0
mesons and other particles previously reported by NA61/SHINE were fitted within the Blast-Wave model. The transverse flow velocities are close to 0.1–0.2 of the speed of light and are significantly smaller than the ones determined in heavy nucleus-nucleus interactions at the same beam momenta.
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