共查询到20条相似文献,搜索用时 31 毫秒
1.
Christine Nattrass 《The European Physical Journal C - Particles and Fields》2009,62(1):265-269
Previous studies have indicated that the near-side peak of high-p
T
triggered correlations can be decomposed into two parts, the Jet and the Ridge. We present data on the yield per trigger of the Jet and the Ridge from d+Au, Cu+Cu and Au+Au collisions at
GeV and 200 GeV and compare data on the Jet to PYTHIA 8.1 simulations for p+p. PYTHIA describes the Jet component up to a scaling factor, meaning that PYTHIA can provide a better understanding of the Ridge by giving insight into the effects of the kinematic cuts. We present collision energy and system dependence of the Ridge yield, which should help distinguish models for the production mechanism of the Ridge. 相似文献
2.
Inclusive cross-sections for gluon jet production are studied numerically in the perturbative QCD pomeron model for pA and central AA collisions at high energies. Two forms for the inclusive cross-sections, with and without emission from the triple pomeron vertex, are compared. The difference was found to reduce to a numerical factor
for momenta below the saturation momentum Q
s. Above Q
s no difference was found at all. For pA collisions the gluon spectrum was found to be
at momenta k below Q
s and
above it. For central AA collisions it was found to be
at momenta k below Q
s and
above it. At large k the spectrum goes like
, flattening with energy. The multiplicities turned out to be proportional to A
0.7 for pA collisions and A for central AA collisions with a good precision. In the latter case they are becoming more peaked at the center with the growth of energy. Their absolute values are high and grow rapidly with energy in accordance with the high value of the BFKL intercept.Received: 12 October 2004, Revised: 22 November 2004, Published online: 21 January 2005 相似文献
3.
Results from RHIC have shown that there is an enhanced baryon/meson ratio in the intermediate transverse momentum range (2<pT<6 GeV/c) in Au+Au collisions at both =130 and 200 GeV. This was initially demonstrated by measurements of the p̄/π- ratio which was then extended in pT by the Λ/K0
S ratio. The data were successfully described by models utilising different hadronization mechanisms: those having recombination
of quarks and others having an interplay between flow, jet quenching and incorporating baryon junction loops. The strange
particle data from the first Au+Au run at =200 GeV gave tantalising hints that the observed enhancement of baryons compared to mesons was diminished by a pT of 6 GeV/c, but a lack of statistics in this range made a definitive statement impossible. Here we present an extended analysis
of identified strange baryons and mesons in Au+Au collisions at =200 GeV using data obtained by the STAR experiment from the 2004 running period. The increase in statistics extends the
measurement of Λ hyperons out to at least 7 GeV/c and K0
S mesons out to 9 GeV/c. This data allows us to place limits on the range where in-vacuum fragmentation functions are applicable
and the effect of baryon dominance is reduced. We also discuss the prospects for making these measurements using multiply-strange
baryons and mesons (Ω and ϕ). 相似文献
4.
G. L. Ma S. Zhang Y. G. Ma X. Z. Cai J. H. Chen C. Zhong 《The European Physical Journal C - Particles and Fields》2008,57(3):589-593
Longitudinal broadening along the Δη direction on the near side in the two-dimensional (Δφ×Δη) di-hadron correlation distribution has been studied for central Au+Au collisions at
GeV, within a dynamical multi-phase transport model. It was found that longitudinal broadening is generated by a longitudinal
flow induced by a strong parton cascade in central Au+Au collisions, to be compared with p+p collisions at
GeV. The longitudinal broadening may shed light on the strongly interacting partonic matter at RHIC. 相似文献
5.
U. Aglietti F. Di Lodovico G. Ferrera G. Ricciardi 《The European Physical Journal C - Particles and Fields》2009,59(4):831-840
By analyzing B→X
u
ℓ
ν
ℓ
spectra with a model based on soft-gluon resummation and an analytic time-like QCD coupling, we obtain
where the first and the second error refer to experimental and theoretical error, respectively. This model successfully describes
the accurate experimental data in beauty fragmentation, which has similar soft-gluon effects. The |V
ub
| value is obtained from the available measured semileptonic branching fractions in limited regions of the phase space. The
distributions in the lepton energy E
ℓ
, the hadron invariant mass m
X
, the light-cone momentum
, together with the double distributions in (m
X
,q
2) and (E
ℓ
,s
hmax ), are used to select the phase-space regions. q
2 is the dilepton squared momentum and s
hmax is the maximal m
X
2 at fixed q
2 and E
ℓ
. The |V
ub
| value obtained is in complete agreement with the value coming from exclusive B decays and from an over-all fit to the standard model parameters. We show that the slight disagreement (up to +2σ) with respect to previous inclusive measurements is not related to different choices for the b (and c) masses, but to a different modeling of the threshold (Sudakov) region. 相似文献
6.
The multiplicity dependence of inclusive spectra of identified hadrons (π, K,
, K
S
0
, and Λ) produced in high-energy
p and pp collisions is studied. Analysis of experimental data on high-p
T hadron cross sections obtained at the Tevatron and RHIC is performed in the framework of z scaling. Independence of the scaling function ψ(z) on the multiplicity density dN
ch/dη is established. The multiplicity density measured in nucleon-nucleon collisions reaches much higher values than the corresponding
quantity [1/(0.5N
p)]dN
ch/dη obtained in heavy-ion collisions. Its influence on particle production reveals properties of self-similarity and fractality.
The relation between the scaling variable z and thermodynamic quantities (“heat capacity” and “temperature”) of the medium associated with the produced inclusive particle
is discussed. Search for z-scaling violation in
p and pp collisions at very high multiplicities as an indication of new-physics phenomena is suggested.
The text was submitted by the authors in English. 相似文献
7.
M. V. Tokarev 《Physics of Atomic Nuclei》2009,72(3):541-551
New experimental data on inclusive cross section of neutral-vector-meson (ω
0, ϕ, K
S
0) production in proton-proton collisions at = 200 GeV obtained at RHIC are analyzed in the framework of z scaling. Properties of z-presentation are used to predict hadron yields over a wide range of transverse momentum p
T
and collisions energy . The next-to-leading-order perturbative QCD calculations of inclusive cross sections of π
0 mesons produced in pp and collisions over a wide range of and p
T
are compared with ISR, S
pS, RHIC data and predictions of z scaling. The dependence of the spectra in p
T
and z presentations for different parton distribution and fragmentation functions is studied. The sensitivity of the obtained results
to the choice of the renormalization (μ
R
), initial-state factorization (μ
F
), and final-state factorization (fragmentation) (μ
H
) scales is verified. It is shown that self-similar features of particle production dictated by the z scaling give strong restriction on the asymptotic behavior of the inclusive spectra in high-p
T
region.
The text was submitted by the author in English. 相似文献
8.
We obtain exact results in α′ for open and closed A-model topological string amplitudes on a large class of toric Calabi-Yau threefolds by using their correspondence with five
dimensional gauge theories. The toric Calabi-Yaus that we analyze are obtained as minimal resolution of cones over Y
p,q
manifolds and give rise via M-theory compactification to SU(p) gauge theories on . As an application we present a detailed study of the local case and compute open and closed genus zero Gromov-Witten invariants of the orbifold. We also display the modular structure of the topological wave function and give predictions for higher genus amplitudes.
The mirror curve in this case is the spectral curve of the relativistic A
1 Toda chain. Our results also indicate the existence of a wider class of relativistic integrable systems associated to generic
Y
p,q
geometries. 相似文献
9.
C. Loizides 《The European Physical Journal C - Particles and Fields》2007,49(1):339-345
We study parton suppression effects in heavy-ion collisions within the parton quenching model (PQM). After a brief summary
of the main features of the model, we present comparisons of calculations for the nuclear modification and the away-side suppression
factor to the data in Au+Au and Cu+Cu collisions at =200 GeV. We discuss properties of light hadron probes and their sensitivity to the medium density within the PQM Monte Carlo
framework. 相似文献
10.
Alakabha Datta David London Joaquim Matias Makiko Nagashima Alejandro Szynkman 《The European Physical Journal C - Particles and Fields》2009,60(2):279-284
Certain B
s
0→V
1
V
2 decays (V
i
is a vector meson) can be related by flavor SU(3) symmetry to corresponding B
d
0→V
3
V
4 decays. In this paper, we show that the final-state polarization can be predicted in the B
s
0 decay, assuming polarization measurements of the B
d
0 decay. This can be done within the scenario of penguin annihilation (PA), which has been suggested as an explanation of the
unexpectedly large transverse polarization in B→φ
K
*. PA is used to estimate the breaking of flavor SU(3) symmetry in pairs of decays. Two of these for which PA makes a reasonably
precise prediction of the size of SU(3) breaking are (B
s
0→φ
φ,B
d
0→φ
K
0*) and (
). The polarization measurement in the B
d
0 decay can be used to predict the transverse polarization in the B
s
0 decay and will allow for testing of PA as well as the other assumptions in the analysis. 相似文献
11.
The production rates and substructure of jets have been studied in charged current deep inelastic e
+
p scattering for Q
2 > 200 GeV2 with the ZEUS detector at HERA using an integrated luminosity of 110.5 pb-1. Inclusive jet cross sections are presented for jets with transverse energies
GeV and pseudorapidities in the range
. Dijet cross sections are presented for events with a jet having
GeV and a second jet having
GeV. Measurements of the mean subjet multiplicity,
, of the inclusive jet sample are presented. Predictions based on parton-shower Monte Carlo models and next-to-leading-order QCD calculations are compared to the measurements. The value of
, determined from
at
for jets with
GeV, is
. The mean subjet multiplicity as a function of Q
2 is found to be consistent with that measured in NC DIS.Received: 5 June 2003, Published online: 10 October 2003 相似文献
12.
13.
During the last decade, as the experimental and computing means and techniques have rapidly evolved, the experimental investigation of the f7/2-shell nuclei has gained renewed interest. TheN = Z nuclei studied with the GASP array range from 44Ti to 52Fe. The results extended the knowledge of their structure up to high spins and excitation energies, above band terminations, where the competition with the charged-particles emission was initially thought to obscure the possibility of gamma-ray spectroscopy investigation. The paper highlights some of the most outstanding properties of these nuclei such as the nuclear rotation and backbending effects, band termination states, yrast traps, non-natural parity bands, competition between T = 0 and T = 1 pn pairing modes.Received: 30 October 2002, Published online: 16 March 2004PACS:
21.10.-k Properties of nuclei; nuclear energy levels - 21.60.Cs Shell model - 23.20.Lv
transitions and level energies - 27.40. + z
C.A. Ur: On leave from NIPNE Bucharest, Romania 相似文献
14.
Xiang Liu Zhi-Gang Luo Yan-Rui Liu Shi-Lin Zhu 《The European Physical Journal C - Particles and Fields》2009,61(3):411-428
We perform a systematic study of the possible molecular states composed of a pair of heavy mesons such as
,
,
in the framework of the meson exchange model. The exchanged mesons include the pseudoscalar, scalar and vector mesons. Through
our investigation, we find the following results. (1) The structure X(3764) is not a molecular state. (2) There exists strong attraction in the range r<1 fm for the
system with J=0,1. If future experiments confirm Z
+(4051) as a loosely bound molecular state, its quantum number is probably J
P
=0+. Its partner state Φ
**0 may be searched for in the π
0
χ
c1 channel. (3) Vector meson exchange provides strong attraction in the
channel together with pion exchange. A bound state solution may exist with a reasonable cutoff parameter Λ∼1.4 GeV. X(3872) may be accommodated as a molecular state dynamically although drawing a very definite conclusion needs further investigation.
(4) The
molecular state may exist. 相似文献
15.
We discuss the difference between n-dimensional regularization and n-dimensional reduction for processes in QCD which have an additional mass scale. Examples are heavy flavor production in hadron-hadron collisions or on-shell photon-hadron collisions where the scale is represented by the mass m. Another example is electroproduction of heavy flavors where we have two mass scales given by m and the virtuality of the photon
. Finally we study the Drell-Yan process where the additional scale is represented by the virtuality
of the vector boson (
). The difference between the two schemes is not accounted for by the usual oversubtractions. There are extra counter terms which multiply the mass scale dependent parts of the Born cross sections. In the case of the Drell-Yan process it turns out that the off-shell mass regularization agrees with n-dimensional regularization.Received: 12 January 2005, Published online: 21 February 2005PACS:
11.15.Bt, 12.38.Bx, 13.85.NiJ. Smith: Partially supported by the National Science Foundation grant PHY-0354776. 相似文献
16.
Dmitry Panchenko 《Journal of statistical physics》2008,130(5):831-842
In Talagrand (J. Stat. Phys. 126(4–5):837–894, 2007) the large deviations limit
for the moments of the partition function Z
N
in the Sherrington-Kirkpatrick model (Sherrington and Kirkpatrick in Phys. Rev. Lett. 35:1792–1796, 1972) was computed for all real a≥0. For a≥1 this result extends the classical physicist’s replica method that corresponds to integer values of a. We give a new proof for a≥1 in the case of the pure p-spin SK model that provides a strong exponential control of the overlap.
This work is partially supported by NSF grant. 相似文献
17.
A new evaluation of the hadronic vacuum polarization contribution to the muon magnetic moment is presented. We take into account the reanalysis of the low-energy e
+
e
-annihilation cross section into hadrons by the CMD-2 Collaboration. The agreement between e
+
e
-and
spectral functions in the
channel is found to be much improved. Nevertheless, significant discrepancies remain in the center-of-mass energy range between 0.85 and
, so that we refrain from averaging the two data sets. The values found for the lowest-order hadronic vacuum polarization contributions are
where the errors have been separated according to their sources: experimental, missing radiative corrections in e
+
e
-data, and isospin breaking. The corresponding Standard Model predictions for the muon magnetic anomaly read
where the errors account for the hadronic, light-by-light (LBL) scattering and electroweak contributions. The deviations from the measurement at BNL are found to be
(1.9
) and
(0.7
) for the e
+
e
-- and
-based estimates, respectively, where the second error is from the LBL contribution and the third one from the BNL measurement.Received: 7 September 2003, Published online: 30 October 2003 相似文献
18.
N. K. Pruthi 《The European Physical Journal C - Particles and Fields》2009,62(1):165-167
In this paper we look for correlations between intermediate p
T
particle pairs and the v
2 of the remaining low p
T
particles. We find that the shape of the flow vector distribution, which is calculated from all low p
T
tracks, depends in a non-trivial way on the angular separation between the high p
T
particle pairs in the event. Our analysis is based on 200 GeV Au+Au collisions measured with the STAR detector. 相似文献
19.
J. Gasser B. Kubis N. Paver M. Verbeni 《The European Physical Journal C - Particles and Fields》2005,40(2):205-227
Motivated by recent experimental results and ongoing measurements, we review the chiral perturbation theory prediction for
decays. Special emphasis is given to the stability of the inner bremsstrahlung-dominated relative branching ratio versus the K
e3 form factors, and on the separation of the structure-dependent amplitude in differential distributions over the phase space. For the structure-dependent terms, an assessment of the order p
6 corrections is given, in particular, a full next-to-leading order calculation of the axial component is performed. The experimental analysis of the photon energy spectrum is discussed, and other potentially useful distributions are introduced.Received: 9 December 2004, Published online: 21 February 2005PACS:
13.20.Eb, 11.30.Rd, 12.39.Fe 相似文献
20.
H. Buesching The PHENIX Collaboration 《The European Physical Journal C - Particles and Fields》2007,49(1):41-45
Over the first five years of operation the PHENIX experiment at RHIC has collected a wealth of data for various systems and
collision energies that is providing valuable information for the understanding of the suppression pattern observed in central
Au+Au collisions at . An overview on transverse-momentum (pT) spectra of π0 and η in different collision energies and systems is presented. 相似文献