共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
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
3.
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
4.
An appropriate kind of curved Hilbert space is developed in such a manner that it admits operators of
- and
-differentiation, which are the analogues of the familiar covariant and D-differentiation available in a manifold. These tools are then employed to shed light on the space-time structure of Quantum
Mechanics, from the points of view of the Feynman ‘path integral’ and of canonical quantisation. (The latter contains, as
a special case, quantisation in arbitrary curvilinear coordinates when space is flat.) The influence of curvature is emphasised
throughout, with an illustration provided by the Aharonov-Bohm effect. 相似文献
5.
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
6.
Pankaj Jain Satish D. Joglekar Subhadip Mitra 《The European Physical Journal C - Particles and Fields》2008,57(4):671-680
We compute the two photon exchange contributions to elastic scattering of polarized electrons from target protons. We use
a non-local field theory formalism for this calculation. The formalism maintains gauge invariance and provides a systematic
procedure for making this calculation. The results depend on one unknown parameter,
. We compute the two photon exchange correction to the ratio of electric to magnetic form factors extracted using polarization
transfer experiments. The correction is found to be small if
. However, for larger values of
, the correction can be quite significant. The correction to the polarization transfer results goes in the right direction
to explain their difference with the ratio measured by the Rosenbluth separation method. We find that the difference between
the two experimental results can be explained for a wide range of values of the parameter
. We also find that the corrections due to two photon exchange depend on the photon longitudinal polarization ε. Hence, we predict an ε dependence of the form factor ratio extracted using the polarization transfer technique. Finally, we obtain a limit on
by requiring that the non-linearity in ε dependence of the unpolarized reduced cross section is within experimental errors. 相似文献
7.
Yichun Xu 《The European Physical Journal C - Particles and Fields》2009,62(1):187-190
We report the transverse momentum (p
T
) distributions for identified charged pions, protons and anti-protons using events triggered by high deposit energy in the
Barrel Electro-Magnetic Calorimeter (BEMC) from p+p collisions at
GeV. The spectra are measured around mid-rapidity (|y|<0.5) over the range of 3<p
T
<15 GeV/c with particle identification (PID) by the relativistic ionization energy loss (rdE/dx) in the Time Projection Chamber (TPC) of the Solenoidal Tracker at RHIC (STAR). The charged pion, proton and anti-proton
spectra at high p
T
are compared with published results from minimum bias triggered events and the Next-Leading-Order perturbative quantum chromodynamic
(NLO pQCD) calculations (DSS, KKP and AKK 2008). In addition, we present the particle ratios of π
−/π
+,
, p/π
+ and
in p+p collisions. 相似文献
8.
P. Gupta B.C. Choudhary S. Chatterji S. Bhattacharya 《The European Physical Journal C - Particles and Fields》2008,53(1):49-58
We present simulation results of γ+jet analysis using CMS (compact muon solenoid) object-oriented software at the large hadron
collider (LHC) center of mass energy = 14 TeV. The study of direct photon production helps in validating the perturbative quantum chromodynamics (pQCD) and providing
information on the gluon distribution in the nucleons. Direct photon processes also constitute a major background to several
other standard model (SM) processes and signals of new physics. Thus these processes need to be understood precisely in the
new energy regime. In this work, we have done a detailed study of the GEANT4 simulated γ+jet events generated with Pythia,
and the related background processes. Isolation cuts have been optimized for direct photon which improves the signal over
background ratio by ∼25% as compared to previous studies done in CMS. The inclusion of a large Δφ cut between the photon and
the leading jet at 40° in the analysis leads to a further increase of ∼15% in S/B, thus giving an overall gain of ∼42% in
S/B ratio. 相似文献
9.
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
10.
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
11.
George Douzas Theodoros Grammatikopoulos George Zoupanos 《The European Physical Journal C - Particles and Fields》2009,59(4):917-935
We consider a
supersymmetric E
8 gauge theory, defined in ten dimensions and we determine all four-dimensional gauge theories resulting from the generalized
dimensional reduction à la Forgacs–Manton over coset spaces, followed by a subsequent application of the Wilson flux spontaneous
symmetry-breaking mechanism. Our investigation is constrained only by the requirements that (i) the dimensional reduction
leads to the potentially phenomenologically interesting, anomaly-free, four-dimensional E
6, SO10 and SU5 GUTs and (ii) the Wilson flux mechanism makes use only of the freely acting discrete symmetries of all possible six-dimensional
coset spaces.
Supported by the EPEAEK II programme IRAKLEITOS.
Partially supported by the NTUA programme for basic research “Karatheodoris” and the European Union’s RTN programme under
contract MRTN-CT-2006-035505. 相似文献
12.
J. Bielcik 《The European Physical Journal C - Particles and Fields》2007,49(1):375-378
The strong suppression of high pT hadrons observed at RHIC has led to the interpretation that energetic partons lose their energy via induced gluon radiation
in the hot and dense matter before fragmenting into hadrons. The study of heavy quark production can extend our understanding
of this scenario. Due to the dead cone effect, the suppression of heavy quark mesons at high pT is expected to be smaller than that observed for charged hadrons at the same energy. The measurement of non-photonic single
electrons up to high pT provides information on charm and beauty production. The semi-leptonic decays of D and B mesons are the dominant contribution
to the non-photonic electron spectra. The preliminary spectra from p+p, d+Au and Au+Au collisions at =200 GeV have been extracted for mid-rapidity non-photonic electrons in the range 1.5<pT (GeV/c)<10. The corresponding nuclear modification factors (RAA) are presented and show a large suppression in central Au+Au collisions, indicating an unexpectedly large energy loss for
heavy quarks in the hot and dense matter created at RHIC. This observed suppression is compared to recent theoretical models.
PACS 13.85.Qk; 13.20.Fc; 13.20.He; 25.75.Dw 相似文献
13.
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
14.
Alejandro?Ayala Eleazar?Cuautle Isabel?Domínguez Antonio?Ortiz Guy?Pai? 《The European Physical Journal C - Particles and Fields》2009,62(3):535-540
The experimental results on transverse momentum azimuthal hadron correlations at RHIC have opened a rich field for parton
energy loss analysis in heavy-ion collisions. Recently, a considerable amount of work has been devoted to study the shapes
of the “away-side” jet which exhibit an interesting and unexpected “double hump” structure not observed in the analogous treatment
of the pp data. Driven by the possibility that the latter result might just mean that such a structure exists already in the case of
pp collisions, but that its relative intensity could be small, here we use the Event Shape Analysis to show that it is possible
to identify and select well defined event topologies in pp collisions, among which a double hump structure for the away-side jet emerges. Using two shape parameters, the sphericity
in the transverse plane and the recoil to analyze a sample of PYTHIA generated pp collisions at
GeV, we show that this structure corresponds to two jets emitted in the backward hemisphere. Finally, we show that Q-PYTHIA
qualitatively reproduces the decrease in the yield of dijet events and the increase of the double hump structure in the away
side observed in heavy-ion collisions. The implications for the treatment of parton energy loss in heavy-ion collisions are
discussed. 相似文献
15.
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
16.
M. X. Chen X. H. Yan S. Wei 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):513-517
Base on the density-functional theory, the structural and magnetic
properties of AunTi2
+ (
) clusters are investigated. The
two titanium atoms form a dimer in the gold clusters. The second-order
energy differences and HOMO-LUMO gap provide a clear explanation of the
abundance peaks and odd-even staggering observed recently in
photofragmentation experiments. The magnetism of AunTi2
+
cluster shows an odd-even effect when n increases from 1 to 4 and drops to
zero at n=5 and 7. The local magnetic moment and charge partition of Ti 4s,
3d orbitals are discussed. The peculiar magnetic properties are related to the
structures and the hybridization between the Au 5d, 6s states and Ti 3d, 4s
states. 相似文献
17.
Antonio Galves Nancy L. Garcia Clémentine Prieur 《Journal of statistical physics》2010,141(4):669-682
We explicitly construct a stationary coupling attaining Ornstein’s [`(d)]\bar{d}-distance between ordered pairs of binary chains of infinite order. Our main tool is a representation of the transition probabilities
of the coupled bivariate chain of infinite order as a countable mixture of Markov transition probabilities of increasing order.
Under suitable conditions on the loss of memory of the chains, this representation implies that the coupled chain can be represented
as a concatenation of i.i.d. sequences of bivariate finite random strings of symbols. The perfect simulation algorithm is
based on the fact that we can identify the first regeneration point to the left of the origin almost surely. 相似文献
18.
Sukanta Dutta Ashok Goyal Mamta 《The European Physical Journal C - Particles and Fields》2009,63(2):305-315
We study the one-loop new physics effects to the CP even triple neutral gauge boson vertices γ
⋆
γ
Z, γ
⋆
Z
Z, Z
⋆
Z
γ and Z
⋆
ZZ in the context of Little Higgs models. We compute the contribution of the additional fermions in Little Higgs models in the
framework of direct product groups where [SU(2)×U(1)]2 gauge symmetry is embedded in SU(5) global symmetry and also in the framework of the simple group where SU(N)×U(1) gauge symmetry breaks down to SU(2)
L
×U(1). We calculate the contribution of the fermions to these couplings when T parity is invoked. In addition, we re-examine the MSSM contribution at the chosen point of SPS1a′ and compare with the SM
and Little Higgs models. 相似文献
19.
M. Miyabe M. Oba H. Iimura K. Akaoka Y. Maruyama I. Wakaida 《Applied Physics A: Materials Science & Processing》2010,101(1):65-70
A cerium oxide sample was ablated by 2nd harmonic radiation of Nd:YAG laser at a power density of 0.1 GW/cm2. Time evolution of the ablation plume was investigated by laser absorption time-of-flight (TOF) measurement. It was found
that the ablated ionic plume in vacuum consisted of two components having different velocities whereas the ablated neutral
atoms had mainly a single component. The flow velocity perpendicular to the sample surface in vacuum was determined to be
3.5 km/s for neutral atoms, and 4.7 km/s and 9.3 km/s for singly charged ions. From the detailed plume evolution in ambient
atmosphere with several pressures we obtained some experimental conditions suitable for isotope analysis of atomic cerium. 相似文献
20.
Paul Sorensen 《The European Physical Journal C - Particles and Fields》2009,61(4):829-833
Recent data from heavy ion collisions at RHIC show strong near-side correlations extending over several units of rapidity.
This ridge-like correlation exhibits an abrupt onset with collision centrality. In this talk, I argue that the centrality
and beam-energy dependence of these near-angle correlations could provide access to information about the Quark Gluon Plasma
phase boundary and the Equation of State of nuclear matter. A beam-energy-scan at RHIC will better reveal the true source
of these correlations and should be a high priority at RHIC. 相似文献