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1.
I. Fröhlich F. Balestra Y. Bedfer R. Bertini L. C. Bland A. Brenschede F. Brochard M. P. Bussa Seonho Choi M. L. Colantoni R. Dressler M. Dzemidzic J.-Cl Faivre A. Ferrero L. Ferrero J. Foryciarz V. Frolov R. Garfagnini A. Grasso S. Heinz W. W. Jacobs W. Kühn A. Maggiora M. Maggiora A. Manara D. Panzieri H.-W. Pfaff G. Piragino A. Popov J. Ritman P. Salabura V. Tchalyshev F. Tosello S. E. Vigdor G. Zosi 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):331-334
Angular distributions for the exclusive reaction
observed via the
decay channel have been measured at
GeV, 2.50 GeV and 2.85 GeV (excess energies Q = 324 MeV, 412 MeV and 554 MeV). The polar angle of the
shows an anisotropy with respect to the beam direction for the lowest energy, which vanishes for the higher energies. The anisotropy of the pp polar angle increases slightly with the beam energy.Received: 30 September 2002, Published online: 22 October 2003PACS:
13.75.Cs Nucleon-nucleon interactions (including antinucleons, deuterons, etc.) - 14.40.Aq
, K, and
mesons - 25.40.Ve Other reactions above meson production thresholds (energies > 400 MeV)Y. Bedfer: Present address: DAPNIA/SPhN, CEA Saclay, France.A. Brenschede: Present address: Syngenio AG, StuttgartF. Brochard: Present address: LPHNHE, Ecole Polytechnique 91128 Palaiseau, France.Seonho Choi: Present address: Temple University, Philadelphia, PA, USA.R. Dressler: Present address: Paul Scherrer Institut, Villigen, CH-5232.J. Foryciarz: Present address: Motorola Polska Software Center, Kraków, Poland.H.-W. Pfaff: Present address: d-fine GmbH, Eschborn. 相似文献
2.
A. Khoukaz I. Geck C. Quentmeier H.-H. Adam A. Budzanowski R. Czyżykiewicz D. Grzonka L. Jarczyk K. Kilian P. Kowina N. Lang T. Lister P. Moskal W. Oelert C. Piskor-Ignatowicz T. Rożek R. Santo G. Schepers T. Sefzick S. Sewerin M. Siemaszko J. Smyrski A. Strzałkowski A. Täschner P. Winter M. Wolke P. Wüstner W. Zipper 《The European Physical Journal A - Hadrons and Nuclei》2004,20(2):345-350
The
-meson production in the reaction
has been studied at excess energies of Q = 26.5, 32.5 and 46.6 MeV using the internal beam facility COSY-11 at the cooler synchrotron COSY. The total cross-sections as well as one angular distribution for the highest Q-value are presented. The excitation function of the near-threshold data can be described by a pure s-wave phase space distribution with the inclusion of the proton-proton final-state interaction and Coulomb effects. The obtained angular distribution of the
-mesons is also consistent with pure s-wave production.Received: 11 August 2003, Revised: 14 November 2003, Published online: 6 April 2004PACS:
13.60.Le Meson production - 13.75.-n Hadron-induced low- and intermediate-energy reactions and scattering (energy
GeV) - 13.85.Lg Total cross-sections - 25.40.-h Nucleon-induced reactions 相似文献
3.
Kinematically complete measurements of the
reaction were performed for beam energies in the range 292-298 MeV. We detected both protons in coincidence by using the large-acceptance COSY-TOF spectrometer and an external proton beam at COSY-JÃ&frac;lich; thus, we measured total and differential cross-sections and energy distributions. A strong enhancement was observed in the Dalitz plots due to the final-state interaction between the two outgoing protons; the data are well reproduced by Monte Carlo simulations using a standard scattering length of a0=-7.83 fm and effective range of r0=2.8 fm. Our measured total cross-sections are roughly
larger than those of recent internal-target experiments at IUCF and CELSIUS. This discrepancy may be due to the final-state interaction pushing some events into the very small-angle region which is almost inaccessible to an internal-target experiment. In the angular distributions we found only very slight deviations from isotropy. The analysis of our momentum distributions yielded a small fraction of
for Ps or Pp wave contributions.PACS:
13.75.Cs Nucleon-nucleon interactions (including antinucleons, deuterons, etc.) - 25.10.+s Nuclear reactions involving few-nucleon systems - 25.40.Ep Inelastic proton scattering - 29.20.Dh Storage rings 相似文献
4.
J. G. Messchendorp 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):417-419
Preliminary differential cross-sections of the reactions
and
with A = 1
H, 12
C, and
nat
Pb are presented. A significant nuclear-mass dependence of the
invariant-mass distribution is found in the
channel. The dependence is not observed in the
channel. The in-medium observation in the
channel is consistent with an in-medium modification of the
interaction in the I = J = 0 channel, changing width and pole position of a
resonant state.Received: 30 September 2002, Published online: 22 October 2003PACS:
13.60.Le Meson production - 21.65. + f Nuclear matterJ.G. Messchendorp: For the TAPS and A2 Collaborations 相似文献
5.
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
6.
V. Yu. Grishina L. A. Kondratyuk M. Büscher W. Cassing 《The European Physical Journal A - Hadrons and Nuclei》2004,21(3):507-520
Using an effective Lagrangian approach as well as the Quark-Gluon Strings Model, we analyze near-threshold production of a
0(980)-mesons in the reaction
as well as the background of non-resonant
-pair production. We argue that the reaction
at an energy release
MeV is dominated by the intermediate production of the a
0(980)-resonance. At larger energies the non-resonant
-pair production --where the kaons are produced in a relative P-wave-- becomes important. The effects of final-state interactions are evaluated in a unitarized scattering length approach and found to be in the order of a 20% suppression close to threshold. Thus, in present experiments at the Cooler Synchrotron COSY-Jülich for
MeV the a
0
+ signal can reliably be separated from the non-resonant
background.Received: 26 February 2004, Published online: 21 September 2004PACS:
25.10. + s Nuclear reactions involving few-nucleon systems - 13.75.-n Hadron-induced low- and intermediate-energy reactions and scattering (energy
GeV) 相似文献
7.
In this brief pedagogical overview the physical basis of the deviation of the nucleon shape from spherical symmetry will be presented along with the experimental methods used to determine it by the
reaction. The fact that non-spherical electric (E2) and Coulomb quadrupole (C2) amplitudes have been observed will be demonstrated. We have measured these multipoles for the
system as a function of Q2 from the photon point through 4 GeV2 with modest precision. Their precise magnitude remains model dependent due to the contributions of the background amplitudes, although rapid progress is being made to reduce these uncertainties. A discussion of what is required to perform a model-independent analysis is presented. All of the data to date are consistent with an oblate shape for the proton and a prolate shape for the
.Received: 1 November 2002, Published online: 15 July 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=0 相似文献
8.
D. V. Bugg 《The European Physical Journal C - Particles and Fields》2004,36(2):161-168
A partial wave analysis of PS185 data for
is presented. A 3
S
1 cusp is identified in the inverse process
at threshold, using detailed balance to deduce cross sections from
. Partial wave amplitudes for
3
P
0, 3
F
3, 3
D
3 and 3
G
3 exhibit a behaviour very similar to resonances observed in Crystal Barrel data. With this identification, the
data then provide evidence for a new I = 0, J
PC
= 1- resonance with mass
MeV,
MeV, coupling to both 3
S
1 and 3
D
1.Received: 4 June 2004, Published online: 9 July 2004 相似文献
9.
P. Pedroni 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):401-404
First measurements of pion photoproduction using circularly polarized photons on longitudinally polarized protons were carried out at MAMI (Mainz) in the energy range
-800 MeV. Results of the helicity dependence of the total inclusive photoabsorption cross-section and of the pion photoproduction channels will be presented. These data provide new input for multipole analyses and determine the main contribution to the Gerasimov-Drell-Hearn integral and the forward spin polarizability
.Received: 30 September 2002, Published online: 22 October 2003PACS:
13.60.Le Meson production - 14.20.Gk Baryon resonances with S = 0P. Pedroni: For the GDH and A2 Collaborations 相似文献
10.
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
11.
We compute the cross section for exclusive double-diffractive
production at the Tevatron,
, and the LHC. We evaluate both the gg and
-channel exchange contributions to the process. The observation of exclusive
production at the Tevatron will provide a check on the model predictions and offer an opportunity to confirm the expectations for exclusive double-diffractive Higgs production at the LHC.Received: 10 September 2004, Revised: 8 October 2004, Published online: 1 December 2004 相似文献
12.
M. J. Vicente Vacas 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):479-481
The
interaction in the scalar isoscalar channel is studied as a function of the baryonic density in the framework of a chiral unitary approach which successfully reproduces vacuum
-
phase shifts. We present some results on the
-meson pole, which is generated dynamically in our model, in nuclear matter. Finally, we analyze the (
) reaction on nucleons and nuclei in the kinematical region where the scalar isoscalar
scattering amplitude is influenced by the low mass of the
in nuclei, and thus, presents a large enhancement close to the position of its pole. Indeed, we find, that the final-state interaction of the pions modified by the nuclear medium produces a large shift of strength of the two-pion invariant-mass distribution in the (
) channel consistent with recent experimental data.Received: 30 September 2002, Published online: 22 October 2003PACS:
14.40.-n Properties of specific particles: Mesons - 25.20.-x Photonuclear reactions - 21.65. + f Nuclear matter 相似文献
13.
S. D. Bass 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):327-329
The light-mass exotics with J
PC
= 1- + observed at BNL and CERN may have a simple explanation as dynamically generated resonances in
rescattering in the final-state interaction. This dynamics is mediated by the same anomalous glue which also generates the large mass of the
. OZI-violating processes are also potentially important to
production in proton-proton collisions close to threshold.Received: 30 September 2002, Published online: 22 October 2003PACS:
12.39.Mk Glueball and nonstandard multi-quark/gluon states - 13.75.Lb Meson-meson interactions - 13.75.Cs Nucleon-nucleon interactions (including antinucleons, deuterons, etc.) 相似文献
14.
A. M. Gasparyan V. Yu Grishina L. A. Kondratyuk W. Cassing 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):305-307
Using the Quark-Gluon Strings Model (QGSM) combined with Regge phenomenology we consider the reactions
and
which are dominated by the contributions of the K
* and D
* Regge trajectories, respectively. The spin structure of the amplitudes is described by introducing Reggeized Born terms. It is found that the existing data for the reaction
are in reasonable agreement with the model predictions. To describe the absolute values of the cross-sections it is necessary to introduce also suppression factors which can be related to absorption corrections. Furthermore, assuming the SU(4) symmetry to hold for Regge residues and the universality of absorption corrections we calculate the cross-section of the reaction
. Employing the latter results from
reactions we then estimate the contributions of the pion exchange mechanism to the cross-sections of the reactions
and
and compare them with the contributions of the K and D exchanges. We find that the NN reactions are dominated not by pion exchange but by K and D exchanges, respectively. Moreover, assuming the SU(4) symmetry to hold approximately for the coupling constants
=
we analyze also the production of leading
-hyperons in the reaction
. It is shown that the non-perturbative mechanism should give an essential contribution to the
yield for
.Received: 30 September 2002, Published online: 22 October 2003PACS:
13.85.Fb Inelastic scattering: two-particle final states - 13.85.Hd Inelastic scattering: many-particle final states - 14.20.Lq Charmed baryons - 14.40.Lb Charmed mesons 相似文献
15.
Measurements of on-shell ZZ production are described, using data from the DELPHI experiment at LEP in e
+
e
- collisions at centre-of-mass energies between 183 and 209 GeV, corresponding to an integrated luminosity of about 665 pb-1. Results obtained in each of the final states
,
,
,
,
, l
+
l
-
l
+
l
-, and
(with
) are presented. The measured production cross-sections are consistent with the Standard Model expectations. These results update and supersede those already published at 183 and 189 GeV.Received: 3 March 2002, Revised: 28 May 2003, Published online: 19 September 2003 相似文献
16.
J. W. Martin 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):425-427
I address the experimental feasibility of two measurements related to the photoproduction of pions, in the context of the G0 experiment. The first involves an extraction of the parity-violating pion-nucleon coupling constant
via a measurement of parity-violating threshold pion photoproduction. The second involves an extraction of
, which parameterizes parity-violating photoproduction of pions on the
-resonance. The second process might have an anomalously large asymmetry, from a model based on hyperon decays.Received: 30 September 2002, Published online: 22 October 2003PACS:
11.30.Er Charge conjugation, parity, time reversal, and other discrete symmetries - 13.60.Le Meson production - 14.20.Gk Baryon resonances with S = 0J.W. Martin: For the G0 Collaboration 相似文献
17.
First results on quark-hadron duality in the spin sector from the HERMES experiment are reported in the range
GeV2 and
GeV2. A complete set of measurements of the generalised GDH integrals for the deuteron, proton and neutron is also shown in the same Q2 range and in the full W2 range.Received: 1 November 2002, Published online: 15 July 2003PACS:
13.60.Hb Total and inclusive cross-sections (including deep-inelastic processes) - 12.38.Qk Experimental tests - 13.88.+e Polarization in interactions and scattering - 25.20.Dc Photon absorption and scatteringA. Fantoni: On behalf of the HERMES Collaboration 相似文献
18.
S. M. Lietti C. A. de S. Pires 《The European Physical Journal C - Particles and Fields》2004,35(1):137-143
In this work, we investigate the sensitivity of the process
at LHC for the photonic 3- and 4-point functions that appear in non-commutative QED. We show that this process serves to study the behavior of the space-space as well as of the space-time non-commutativity. We also show that this process can probe the non-commutative scale
in the range of a few TeV.Received: 9 February 2004, Revised: 27 February 2004, Published online: 8 April 2004 相似文献
19.
Di-jet production is studied in collisions of quasi-real photons at e + e- centre-of-mass energies
from 189 to 209 GeV at LEP. The data were collected with the OPAL detector. Jets are reconstructed using an inclusive
-clustering algorithm for all cross-section measurements presented. A cone jet algorithm is used in addition to study the different structure of the jets resulting from either of the algorithms. The inclusive di-jet cross-section is measured as a function of the mean transverse energy
of the two leading jets, and as a function of the estimated fraction of the photon momentum carried by the parton entering the hard sub-process,
, for different regions of
. Angular distributions in di-jet events are measured and used to demonstrate the dominance of quark and gluon initiated processes in different regions of phase space. Furthermore the inclusive di-jet cross-section as a function of
and
is presented, where
is the jet pseudo-rapidity. Different regions of the
-
-space are explored to study and control the influence of an underlying event. The results are compared to next-to-leading order perturbative QCD calculations and to the predictions of the leading order Monte Carlo generator PYTHIA.Received: 20 December 2002, Published online: 17 October 2003 相似文献
20.
Approximately 438 pb-1 of e + e- data from the OPAL detector, taken with the LEP collider running at centre-of-mass energies of 192-209 GeV, are analyzed to search for evidence of chargino pair production,
, or neutralino associated production,
. Limits are set at the 95% confidence level on the product of the cross-section for the process
and its branching ratios to topologies containing jets and missing energy, or jets with a lepton and missing energy, and on the product of the cross-section for
and its branching ratio to jets. R-parity conservation is assumed throughout this paper. When these results are interpreted in the context of the Constrained Minimal Supersymmetric Standard Model, limits are also set on the masses of the
and
, and regions of the parameter space of the model are ruled out. Nearly model-independent limits are also set at the 95% confidence level on
with the assumption that each chargino decays via a W boson, and on
with the
assumed to decay via a Z0.Received: 15 December 2003, Revised: 16 February 2004, Published online: 23 April 2004 相似文献