共查询到20条相似文献,搜索用时 78 毫秒
1.
E. F. Lütz S. S. Rocha A. R. Taurines G. F. Marranghello M. Dillig C. A. Z. Vasconcellos 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):483-485
We investigate dense hadronic matter in a relativistic mean-field approach. For a generalized baryon-meson Lagrangian effective field theory, we confront expansions from naive dimensional analysis for the nonlinear self-couplings of the
,
fields with estimates from microscopic
pair creation models from Quantum Chromodynamics. Upon adjusting the model parameters to ordinary nuclear matter, we discuss implications of the approach to dense hadronic matter and in particular to neutron stars.Received: 30 September 2002, Published online: 22 October 2003PACS:
11.10.-z Field theory - 21.65. + f Nuclear matter - 26.60. + c Nuclear matter aspects of neutron stars 相似文献
2.
V. A. Khoze W. J. Stirling P. H. Williams 《The European Physical Journal C - Particles and Fields》2003,31(1):91-101
We consider the hadronic radiation patterns for the generic process of
forward jet production at the LHC, where the (centrally produced)
originate either from a Higgs, a Z or from standard QCD production processes. A numerical technique for evaluating the radiation patterns for non-trivial final states is introduced and shown to agree with the standard analytic results for more simple processes. Significant differences between the radiation patterns for the Higgs signal and the background processes are observed and quantified. This suggests that hadronic radiation patterns could be used as an additional diagnostic tool in Higgs searches in this channel at the LHC.Received: 25 July 2003, Published online: 26 September 2003 相似文献
3.
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
4.
A simple coalescence model based on the same diagrammatic approach of antimatter production in hadronic collisions as used previously for antideuterons is used here for the hadroproduction of mass-3 antinuclei. It is shown that the model is able to reproduce the existing experimental data on the
and
production without any additional parameter.Received: 28 January 2003, Revised: 10 July 2003, Published online: 18 November 2003PACS:
24.10.-i Nuclear reaction models and methods 相似文献
5.
The ratio is measured by comparing the production rates of the π0 in the two decay channels. The analysis is based on approximately four million hadronic decays of the Z boson recorded by
the ALEPH detector in the years 1991 to 1995. The value of is determined to be . A recalculation of the Particle Data Group world average gives rise to a slightly improved error, and moves the world average
closer to the theoretical value. 相似文献
6.
The hadronic annihilation branching-ratios in quasi-two-body final states have been obtained from the observation of the reactions
,
at rest in hydrogen targets at different densities. The enhancement or suppression of specific hadronic channels connected to dynamical selection rules is observed in the production of different resonances both in protonium S and P-waves, systematically investigated for the first time. Besides the well known
and
enhancement from 3S1 and 1S0 partial waves, the dominance of one isospin source in
production, well established from S-waves, is confirmed also in P-waves (1S0, I = 0; 3S1, I = 1; 1P1, I = 0; 3P1, I = 0; 3P2, I = 1). In addition, the experimental data clearly show a strong suppression of
and
final states from P-wave which has a remarkable coincidence with
pattern production.Received: 4 February 2004, Published online: 5 May 2004 相似文献
7.
8.
P. Aurenche J. -P. Guillet M. Fontannaz 《Zeitschrift fur Physik C Particles and Fields》1994,64(4):621-630
We discuss in detail the photon structure function beyond the leading logarithm approximation. Of special concern is the factorization scheme and the hadronic input; we show how to naturally absorb large terms due to the
factorization scheme in a modified hadronic component. The effect of the charm quark mass threshold is also discussed in relation to the phenomenology. A comparison with data shows that the modified hadronic component can be reasonably described by a VDM-type input.URA 14-36 du CNRS, associée à l'Ecole Normale Supérieure de Lyon, et au Laboratoire d'Annecy-le-Vieux de Physique des Particules 相似文献
9.
K. Christensen N. Farid G. Pruessner M. Stapleton 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):331-336
We derive general properties of the finite-size scaling of
probability density functions and show that when the apparent
exponent
of a probability density is less than 1, the
associated finite-size scaling ansatz has a scaling exponent τ
equal to 1, provided that the fraction of events in the universal
scaling part of the probability density function is non-vanishing in
the thermodynamic limit.
We find the general result that τ≥1 and
.
Moreover, we show that if the scaling function
approaches a
non-zero constant for small arguments,
, then
.
However, if the scaling function vanishes for small arguments,
, then τ= 1, again assuming a
non-vanishing fraction of universal events.
Finally, we apply the formalism developed to examples from the literature,
including some where misunderstandings of the theory of scaling have led to erroneous conclusions. 相似文献
10.
The decay chain
is identified in a sample of 3.9 million hadronic Z decays collected with the OPAL detector at LEP. The branching ratio BR
is measured to be
for the J
P
=1+ (D0
1) state. For decays into the J
P
=2+ (D2
*0) state, an upper limit of 1.4 x 10-3 is placed on the branching ratio at the 95% confidence level.Received: 20 December 2002, Revised: 15 April 2003, Published online: 12 September 2003 相似文献
11.
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
12.
We investigate the QED Compton process (QEDCS) in
and
, together with the major background coming from virtual Compton scattering (VCS), where the photon is emitted from the hadronic vertex. We suggest new kinematical constraints which suppress the VCS background and are furthermore suitable for the extraction of the equivalent photon content of the proton at the HERA collider. We show that the cross section, commonly expressed in terms of the proton structure functions, is reasonably well described by the equivalent photon approximation of the proton, also in the inelastic channel in the proposed kinematical region.Received: 5 February 2004, Revised: 8 March 2004, Published online: 9 June 2004 相似文献
13.
C. N. Papanicolas 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):141-145
The conjectured deformation of hadrons and its experimental verification offer a particularly fertile ground for understanding the intricate dynamics of their constituents and QCD at the confiment scale. The detailed study of the
transition is viewed as the preferred method of experimental investigation of this central issue in hadronic physics. A brief overview of the field is presented, followed by a presentation of the most recent results from Bates
program. The new Bates/OOPS data at Q
2 = 0.127 GeV/c
2) yield
and
and they exclude a spherical nucleon and/or
. The magnitude and the origin of the deformation is the focus of the ongoing and planned investigations.Received: 30 September 2002, Published online: 22 October 2003PACS:
13.60.Le Meson production - 13.88. + e Polarization in interactions and scattering - 13.40.Gp Electromagnetic form factors - 14.20.Gk Baryon resonances with S = 0C.N. Papanicolas: Invited plenary talk 相似文献
14.
J. Ellis F. Moortgat G. Moortgat-Pick J. M. Smillie J. Tattersall 《The European Physical Journal C - Particles and Fields》2009,60(4):633-651
We study the potential observation at the LHC of CP-violating effects in stop production and subsequent cascade decays,
,
,
, within the Minimal Supersymmetric Standard Model. We study T-odd asymmetries based on triple products between the different
decay products. There may be a large CP asymmetry at the parton level, but there is a significant dilution at the hadronic
level after integrating over the parton distribution functions. Consequently, even for scenarios where large CP intrinsic
asymmetries are expected, the measurable asymmetry is rather small. High luminosity and precise measurements of masses, branching
ratios and CP asymmetries may enable measurements of the CP-violating parameters in cascade decays at the LHC. 相似文献
15.
We prove the collinear factorization theorem for the process
at the twist-3 level in the covariant gauge by means of the Ward identity, concentrating on the two-parton case. It is shown that soft divergences cancel and collinear divergences are grouped into the pseudo-scalar and pseudo-tensor two-parton twist-3 pion distribution amplitudes. The delicate summation of a complete set of diagrams for achieving factorization in momentum, spin, and color spaces is emphasized. The proof is then extended to the exclusive semileptonic decay
, assuming the hard scale to be of
, where
is a hadronic scale and M
B
the B meson mass. We explain the distinction between the factorization of collinear divergences for a pion distribution amplitude and of soft divergences for a B meson distribution amplitude. The gauge invariance and universality of the two-parton twist-3 pion distribution amplitudes are confirmed. The proof presented here can accommodate the leading twist-2 case. We then compare our proof with that performed in the framework of soft-collinear effective theory.Received: 8 June 2004, Revised: 10 December 2004, Published online: 3 March 2005PACS:
12.38.Bx 相似文献
16.
Chao-Hsi Chang Jiao-Kai Chen Zhen-Yun Fang Bing-Quan Hu Xing-Gang Wu 《The European Physical Journal C - Particles and Fields》2007,50(4):969-978
The light top-squark may be the lightest squark, and its lifetime may be ‘long enough’ in a kind of SUSY models that have not been ruled out yet
experimentally, so colorless ‘supersymmetric hadrons (superhadrons)’ (q is a quark excluding the t-quark) may be formed as long as the light top-squark can be produced. The fragmentation function of into heavy ‘supersymmetric hadrons (superhadrons)’ (Q̄=c̄ or b̄) and hadronic production of the superhadrons are investigated quantitatively. The fragmentation function is
calculated precisely. Due to the difference in spin of the SUSY component, the asymptotic behavior of the fragmentation function
is different from those of the existing ones. The fragmentation function is also applied to compute the production of heavy
superhadrons at the hadronic colliders Tevatron and LHC in the so-called fragmentation approach. The resultant cross-section
for the heavy superhadrons is too small to observe at Tevatron, but large enough at LHC, when all the relevant parameters
in the SUSY models are taken within the favored region for the heavy superhadrons. The production of ‘light superhadrons’
(q=u,d,s) is also roughly estimated with the same SUSY parameters. It is pointed out that the production cross-sections of
the light superhadrons may be much greater than those of the heavy superhadrons, so that even at Tevatron the light superhadrons may be produced
in great quantities.
PACS 12.38.Bx; 13.87.Fh; 12.60.Jv; 14.80.Ly 相似文献
17.
M. Boglione M. R. Pennington 《The European Physical Journal C - Particles and Fields》2003,30(4):503-512
A guide to the composition of the enigmatic f
0(980) and a
0(980) states is their formation in
-radiative decays. Precision data are becoming available from the KLOE experiment at the DA
NE machine at Frascati, as well as results from SND and CMD-2 at VEPP-2M at Novosibirsk. We show how the coupling of the f
0(980) to this channel can be extracted from these, independently of the background provided by
production. To do this we use the fact that the behaviour of both the f
0(980) and
cannot be determined by these data alone, but is strongly constrained by experimental results from other hadronic processes as required by unitarity. We find that the resulting coupling for the
is
GeV with a background that is quite unlike that assumed if unitarity is neglected. This provides an object lesson in how unitarity teaches us to add resonances. Not surprisingly the result is crucially dependent on the pole position of the f
0(980), for which there are still sizeable uncertainties. At present this leads to an uncertainty in the
branching ratio which can only be fixed by further precision data on the f
0(980). Nevertheless, the
is now the same order of magnitude as the experimental
.Received: 25 March 2003, Published online: 5 September 2003 相似文献
18.
A study of
quark hadronisation is presented using inclusively reconstructed B hadrons in about four million hadronic Z decays recorded in 1992-2000 with the OPAL detector at LEP. The data are compared to different theoretical models, and fragmentation function parameters of these models are fitted. The average scaled energy of weakly decaying B hadrons is determined to be
Received: 31 July 2002, Published online: 3 July 2003 相似文献
19.
We report the OPE-based predictions for a number of lepton energy and hadronic mass moments in the inclusive semileptonic
decays with a lower cut on the charged lepton energy. We rely on the direct OPE approach where no expansion in the charm mass is employed and the theoretical input is a limited set of underlying OPE parameters including mb and mc. A Wilsonian treatment with a hard cutoff is applied using running low-scale masses
and a kinetic expectation value
. This leaves for perturbative corrections only genuinely short-distance effects and makes them numerically small. Predictions are also given for the modified hadronic moments of the kinematic variable
which is a combination of MX2 and EX. The measurement of such moments would allow a more reliable extraction to be made of higher-order non-perturbative heavy quark parameters from experiment.Received: 13 January 2004, Published online: 3 March 2004N. Uraltsev: On leave of absence from St. Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg 188300, Russia. 相似文献
20.
P. F. Yu J. G. Cai J. M. Liu G. T. Shen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(1):151-158
We investigate the phase decoherence effects on
the entanglement of a two-qubit anisotropic Heisenberg
model
with a nonuniform magnetic field in the x–z-plane. As a
measure of the entanglement, the concurrence of the system is
calculated. It is shown that when the magnetic field is along the
z-axis, the nonuniform and uniform components of the field have
no influence on the entanglement for the cases of
and
, respectively. But when
the magnetic field is not along the z-axis, both the uniform and
the nonuniform components of the field will introduce the
decoherence effects. It is found that the effects of the
Heisenberg chain's anisotropy in the Z-direction on the
entanglement are dependent on the direction of the field.
Moreover, the larger the initial concurrence is, the higher value
it will exhibit during the time evolution of the system for a
proper set of the parameters ν, Δ, θ, γ
, B and b. 相似文献