共查询到20条相似文献,搜索用时 15 毫秒
1.
R. Belmont 《The European Physical Journal C - Particles and Fields》2009,62(1):243-248
In Run-7 of RHIC operations PHENIX has recorded over 5.4 billion minimum bias events, facilitating a detailed study of deuteron
and antideuteron production as a function of centrality and up to transverse momentum of p
T
=5 GeV/c. We present transverse momentum p
T
and transverse mass m
T
spectra, mean transverse momentum 〈p
T
〉, source parameters, particle ratios, and nuclear modification factor R
CP
. Deuteron and antideuteron spectra are compared to those of other identified particles and to hydrodynamical predictions. 相似文献
2.
F.?Fayette M.?W.?Krasny W.?P?aczek A.?Siódmok 《The European Physical Journal C - Particles and Fields》2009,63(1):33-56
This paper is the second of the series of papers proposing dedicated strategies for precision measurements of the Standard Model parameters at the LHC. The common feature of these strategies is their robustness
with respect to the systematic measurement and modeling error sources. Their impact on the precision of the measured parameters
is reduced using dedicated observables and dedicated measurement procedures which exploit flexibilities of the collider and
detector running modes. In the present paper we focus our attention on the measurement of the charge asymmetry of the W-boson mass. This measurement is of primordial importance for the LHC experimental program, both as a direct test of the charge-sign-independent
coupling of the W-bosons to the matter particles and as a necessary first step towards the precision measurement of the charge-averaged W-boson mass. We propose and evaluate the LHC-specific strategy to measure the mass difference between the positively and negatively
charged W-bosons,
MW+-MW-M_{W^{+}}-M_{W^{-}}
. We show that its present precision can be improved at the LHC by a factor of 20. We argue that such a precision is beyond
the reach of the standard measurement and calibration methods imported to the LHC from the Tevatron program. 相似文献
3.
M.J. Russcher 《The European Physical Journal C - Particles and Fields》2007,49(1):231-234
Results are presented of an ongoing analysis of direct photon production in =200 GeV deuteron-gold collisions (d+Au) with the STAR experiment at RHIC. A significant excess of direct photons is observed
near mid-rapidity (0<y<1) and found to be consistent with next-to-leading order pQCD calculations including the contribution
from fragmentation photons.
PACS 25.75.-q 相似文献
4.
C. Zhong 《The European Physical Journal C - Particles and Fields》2007,49(1):389-391
We report on the first measurement of single muon from charm semileptonic decays at low transverse momentum (pT) in =200 GeV Au+Au collisions. Muon identification was obtained using the STAR time projection chamber in conjunction with a
time-of-flight detector. The pT spectra of electron and muon from charm semileptonic decays are presented. The measured D→μ+X at pT<0.25 GeV/c greatly constrains the charm total cross section. The charm differential cross section dσcc/dy is found to be consistent with the number of binary collision scaling.
PACS 25.75.Dw; 25.75.-q 相似文献
5.
A. Toia 《The European Physical Journal C - Particles and Fields》2007,49(1):243-247
The first measurement of the dielectron continuum at RHIC energies was performed by the PHENIX experiment for Au+Au collisions
at =200 GeV. Mass spectra for different centralities are presented and compared with the expectations from hadron decays. 相似文献
6.
F. Benedosso 《The European Physical Journal C - Particles and Fields》2007,49(1):61-64
We present measurements of azimuthal correlations between photons (from π0 decay) and charged hadrons in d+Au collisions at =200 GeV. We use di-hadron correlations to study parton fragmentation in d+Au collisions at RHIC. Specifically, the near-side
and away-side peaks of the azimuthal angular difference distribution are used to measure the root-mean-squared (RMS) fragmentation
transverse momentum and the mean intrinsic parton transverse momentum . The measurements with leading photons are compared to results using leading charged particles.
PACS 25.75.-q 相似文献
7.
The "good" diquark is employed to study A+ baryons within a mass loaded flux tube model. The study indicates that all A+ baryons candidates in the 2008 review by the Particle Data Group (PDG) are well described in the mass loaded flux model. The quantum numbers JP of these A+ candidates are assigned. If Ac(2765)+ is an orbitally excited A+, it is likely the JP=3/2+one. If ∧c(2765)+ is an orbitally excited ∑c, there ought to be another JP=3/2+∧c+with mass ≈2770 MeV. In the model, there exists no JP=1/2+∧c+(≈2700)predicted in existing literature. Ac (2940)+ is very possible the orbitally excited baryon with 相似文献
8.
Catherine Silvestre 《The European Physical Journal C - Particles and Fields》2009,61(4):841-845
In this paper, we calculate the decay rates of the D
+→D
0
e
+
ν, D
S
+→D
0
e
+
ν,
, D
S
+→D
+
e
−
e
+ and B
S
0→B
0
e
−
e
+ semileptonic decay processes, in which only the light quarks decay, while the heavy flavors remain unchanged. The branching
ratios of these decay processes are calculated with the flavor SU(3) symmetry. The uncertainties are estimated by considering
the SU(3) breaking effect. We find that the decay rates are very tiny in the framework of the standard model. We also estimate
the sensitivities of the measurements of these rare decays at future experiments, such as BES-III, super-B and LHC-b. 相似文献
9.
Kimball A. Milton Inés Cavero-Peláez Prachi Parashar K. V. Shajesh J. Wagner 《International Journal of Theoretical Physics》2011,50(4):963-973
The construction of PT\mathcal{PT}-symmetric quantum electrodynamics is reviewed. In particular, the massless version of the theory in 1+1 dimensions (the Schwinger
model) is solved. Difficulties with unitarity of the S-matrix are discussed. 相似文献
10.
L. Gaillard 《The European Physical Journal C - Particles and Fields》2007,49(1):51-55
Here we present initial studies of two-dimensional angular correlations of Λ, Λ̄, and K0
Short triggers with unidentified charged hadrons in Au+Au collisions at =200 GeV measured by STAR. Distributions of pseudo-rapidity difference, Δη, and azimuthal separation, Δφ, are constructed
containing structures observed in unidentified hadron correlations, including a jet peak at small Δη-Δφ accompanied by a flow-like
ridge extended over Δη. These features are studied as a function of centrality via integrated yields and fitting to projections
onto Δη and Δφ axes. Yields are found to be consistent with unidentified correlation analyses, and no clear distinction is
observed between the three species.
PACS 25.75.Gz 相似文献
11.
We investigate the occurrence of Hunds rule magnetism in C
molecular ions, by computing the ground-state spin for all charge states n from -3 to +5. The two competing interactions, electron-vibration (e-v, including Jahn Teller, favoring low spin) and electron-electron (e-e, including Hund-rule exchange, favoring high spin), are accounted for based on previously computed ab initio coupling parameters. Treating the ion coordinates as classical, we first calculate and classify the static Jahn-Teller distorted states for all n, inclusive of both e-v and e-e effects. We then correct the adiabatic result by including the zero-point energy lowering associated with softening of vibrations at the adiabatic Jahn-Teller minima. Our overall result is that while, like in previous investigations, low-spin states prevail in negative ions, Hunds rule high spin dominates all positive C60
n+ ions. This suggests also that Hund-rule magnetism could arise in fullerene cation-based solid state compounds, particularly those involving C60
2+.Received: 17 April 2003, Published online: 22 September 2003PACS:
36.40.Cg Electronic and magnetic properties of clusters - 61.48.+c Fullerenes and fullerene-related materials (structure) - 71.20.Tx Fullerenes and related materials; intercalation compounds (electronic structure) - 75.75.+a Magnetic properties of nanostructures 相似文献
12.
The hadronic decays η,
↦3π and
↦ηππ are investigated within the framework of U(3) chiral effective field theory in combination with a relativistic coupled-channels approach. Final state interactions are
included by deriving s- and p-wave interaction kernels for meson-meson scattering from the chiral effective Lagrangian and iterating them in a Bethe-Salpeter
equation. Very good overall agreement with currently available data on decay widths and spectral shapes is achieved. 相似文献
13.
Qing-hai Wang 《International Journal of Theoretical Physics》2011,50(4):1005-1011
The relation between the P\ensuremath{\mathcal{P}}
T\ensuremath{\mathcal{T}} symmetry and Hermiticity is discussed. In the finite-dimensional linear space, any Hermitian matrix is a special case of
P\ensuremath{\mathcal{P}}
T\ensuremath{\mathcal{T}}-symmetric matrices. Explicit results in 2×2 are shown. The early belief that the P\ensuremath{\mathcal{P}}
T\ensuremath{\mathcal{T}}-symmetric quantum mechanics is a generalization of the conventional Hermitian quantum mechanics is confirmed. 相似文献
14.
Hiroshi Masui 《The European Physical Journal C - Particles and Fields》2009,62(1):169-173
One of the most striking results is the large elliptic flow (v
2) at RHIC. Detailed mass and transverse momentum dependence of elliptic flow are well described by ideal hydrodynamic calculations
for p
T<1 GeV/c, and by parton coalescence/recombination picture for p
T=2–6 GeV/c. The systematic error on v
2 is dominated by so-called “non-flow effects”, which are correlations other than flow, such as resonance decays and jets.
It is crucial to understand and reduce the systematic error from non-flow effects in order to understand the underlying collision
dynamics. In this paper, we present the centrality dependence of v
2 with respect to the first harmonic event plane at ZDC-SMD (v
2{ZDC-SMD}) in Au + Au collisions at
GeV. A large rapidity gap (|Δη|>6) between midrapidity and the ZDC-SMD could enable us to minimize possible non-flow contributions. We compare the results
of v
2{ZDC-SMD} with v
2{BBC}, which is measured by event plane determined at |η|=3.1–3.9. Possible non-flow contributions in those results will be discussed. 相似文献
15.
The E2 algebra has three elements, J, u, and v, which satisfy the commutation relations [u,J]=iv, [v,J]=−iu, [u,v]=0. We can construct the Hamiltonian H=J
2+gu, where g is a real parameter, from these elements. This Hamiltonian is Hermitian and consequently it has real eigenvalues. However,
we can also construct the PT\mathcal{P}\mathcal{T}-symmetric and non-Hermitian Hamiltonian H=J
2+igu, where again g is real. As in the case of PT\mathcal{P}\mathcal{T}-symmetric Hamiltonians constructed from the elements x and p of the Heisenberg algebra, there are two regions in parameter space for this PT\mathcal{P}\mathcal{T}-symmetric Hamiltonian, a region of unbroken PT\mathcal{P}\mathcal{T} symmetry in which all the eigenvalues are real and a region of broken PT\mathcal{P}\mathcal{T} symmetry in which some of the eigenvalues are complex. The two regions are separated by a critical value of g. 相似文献
16.
T. Mannel B. D. Pecjak A. A. Pivovarov 《The European Physical Journal C - Particles and Fields》2011,71(4):1607
We use QCD sum rules to compute the matrix elements of the ΔB=2 operators appearing in the heavy-quark expansion of the width difference of the B
s
mass eigenstates. The main focus of our analysis is on the subleading operators R
2 and R
3, which appear at next-to-leading order in the 1/m
b
expansion. The matrix elements of these operators are already essential for precise phenomenology, but their calculation
in lattice QCD is lacking and the values given here provide a first estimate of their values. We conclude that the violation
of the factorization approximation for these matrix elements due to non-perturbative vacuum condensates is as low as 1–2%. 相似文献
17.
A. G. Knospe 《The European Physical Journal C - Particles and Fields》2009,62(1):223-227
Heavy-flavor semileptonic decays are expected to dominate the spectrum of non-photonic electrons produced from collisions
at the energies of the Relativistic Heavy Ion Collider. The non-photonic electron yield is suppressed by approximately a factor
of 5 in central Au + Au events at
GeV relative to p+p events with the same collision energy. Most theoretical models predict less non-photonic-electron suppression than is observed
experimentally. We present a preliminary measurement of the yield of non-photonic electrons in Cu + Cu events at
GeV, as well as the nuclear modification factor. 相似文献
19.
Abdullah Algin 《International Journal of Theoretical Physics》2009,48(1):71-84
We discuss the algebras, representations, and thermodynamics of quantum group bosonic gas models with two different symmetries:
GL
p,q
(2) and
. We establish the nature of the basic numbers which follow from these GL
p,q
(2)- and
-invariant bosonic algebras. The Fock space representations of both of these quantum group invariant bosonic oscillator algebras
are analyzed. It is concisely shown that these two quantum group invariant bosonic particle gases have different algebraic
and high-temperature thermo-statistical properties. 相似文献
20.
de Florian Daniel Fidanza Nerina Hernández-Pinto Roger Mazzitelli Javier Habarnau Yamila Rotstein Sborlini Germán 《The European Physical Journal C - Particles and Fields》2013,73(4):1-5
We analyze a noncommutative model of BTZ spacetime based on deformation of the standard symplectic structure of phase space, i.e., a modification of the standard commutation relations among coordinates and momenta in phase space. We find a BTZ-like solution that is nonperturbative in the non-trivial noncommutative structure. It is shown that the use of deformed commutation relations in the modified non-canonical phase space eliminates the horizons of the standard metric. 相似文献