共查询到20条相似文献,搜索用时 31 毫秒
1.
V.A. Khoze A.D. Martin M.G. Ryskin 《The European Physical Journal C - Particles and Fields》2002,24(3):459-468
The rich structure of photon-exchange processes at hadron colliders is studied. We discuss central vector meson production
, W production and production. Each process has distinct, and large, soft pp rescattering effects, which can be directly observed by detecting the outgoing protons. This allows a probe of the optical
density of the proton, which plays a crucial role in the evaluation of the rapidity gap survival probabilities in diffractive-like
processes at hadron colliders. We note that an alternative mechanism for production is odderon, instead of photon, exchange; and that the ratio of odderon to photon contributions is enhanced (suppressed)
for vector meson production.
Received: 1 February 2002 / Revised version: 4 April 2002 / Published online: 22 May 2002 相似文献
2.
V.A. Khoze A.D. Martin M.G. Ryskin 《The European Physical Journal C - Particles and Fields》2002,23(2):311-327
We study the double-diffractive production of various heavy systems (e.g. Higgs, dijet, and SUSY particles) at LHC and Tevatron collider energies. In each case we compute the probability that the rapidity gaps,
which occur on either side of the produced system, survive the effects of soft rescattering and QCD bremsstrahlung effects.
We calculate both the luminosity for different production mechanisms, and a wide variety of subprocess cross sections. The
results allow numerical predictions to be readily made for the cross sections of all these processes at the LHC and the Tevatron
collider. For example, we predict that the cross section for the exclusive double-diffractive production of a 120 GeV Higgs boson at the LHC is about 3 fb, and that the QCD background in the decay mode is about 4 times smaller than the Higgs signal if the experimental missing-mass resolution is 1 GeV. For completeness
we also discuss production via or WW fusion.
Received: 7 November 2001 / Revised version: 11 December 2001 / Published online: 25 January 2002 相似文献
3.
V.A. Khoze A.D. Martin M.G. Ryskin 《The European Physical Journal C - Particles and Fields》2000,14(3):525-534
Double diffractive Higgs production at pp (or ) colliders continues to attract attention as a potential signal in the search for the boson. We present improved perturbative
QCD estimates of the event rates for both the exclusive and inclusive double diffractive Higgs processes, paying particular
attention to the survival probability of the rapidity gaps. We find that the major uncertainty is in the prediction for the
survival probability associated with soft rescattering. We show that an analogous process, the double diffractive production
of a pair of jets with large values of , has an event rate which makes it accessible at the Tevatron. Observation of this process can therefore be used as a luminosity
monitor for two-gluon exchange processes, such as the production of a Higgs boson with rapidity gaps on either side.
Received: 8 February 2000 / Published online: 14 April 2000 相似文献
4.
V. A. Khoze A. D. Martin M. G. Ryskin 《The European Physical Journal C - Particles and Fields》2004,34(3):327-334
We study the central diffractive production of the (three neutral) Higgs bosons, with a rapidity gap on either side, in an MSSM scenario with CP-violation. We consider the
and
decay for the light H1 boson and the four b-jet final state for the heavy H2 and H3 bosons, and discuss the corresponding backgrounds. A direct indication of the existence of CP-violation can come from the observation of either an azimuthal asymmetry in the angular distribution of the tagged forward protons (for the exclusive
process) or of a
contribution in the azimuthal correlation between the transverse energy flows in the proton fragmentation regions for the process with the diffractive dissociation of both incoming protons (
). We emphasise the advantage of reactions with the rapidity gaps (that is, production by pomeron-pomeron fusion) to probe CP-parity and to determine the quantum numbers of the produced central object.Received: 16 January 2004, Published online: 31 March 2004 相似文献
5.
6.
L. Stroe G. Lhersonneau A. Andrighetto P. Dendooven J. Huikari H. Penttilä K. Peräjärvi L. Tecchio Y. Wang 《The European Physical Journal A - Hadrons and Nuclei》2003,17(1):57-63
Cross-sections for the production of neutron-rich nuclei obtained by neutron-induced fission of natural uranium have been
measured. The neutrons were generated by bombarding a 13C target with 55 MeV protons. The results, position of the maximum in the (Z, A)-plane, width and magnitude, are very comparable with those where the neutrons are generated by bombardment of natural 12C graphite with 50 MeV deuterons. Depending on the geometry of the converter/target assembly the isotope yields, however,
are a factor of 2-3 lower due to less efficient production of neutrons per primary projectile, especially at small forward
angles.
Received: 8 November 2002 / Accepted: 20 December 2002 / Published online: 15 April 2003 相似文献
7.
E. Caurier F. Nowacki A. Poves 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):145-150
Recent shell model calculations for the neutron-rich nuclei around the magic numbers N = 20, N = 28 and N = 40 are reviewed. We stress two points: i) The crucial role played by the monopole part of the effective interaction that
determines the evolution of the spherical mean field. In particular, the reduction in the quasiparticle gaps at the magic
numbers can erode or even erase the shell closures. ii) The rich variety of structures that can be found in these situations,
with coexisting deformed and spherical states, rapid changes of behaviour with N or Z, and the massive occurrence of intruder states as ground states.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: alfredo.poves@uam.es 相似文献
8.
bstract The azimuthal asymmetry of a minijet system produced at the early stage of nucleon-nucleon and nuclear collisions in a central
rapidity window is studied. We show that, in pp collisions, the minijet-transverse-energy production in a central rapidity window is essentially unbalanced in azimuth because
of asymmetric contributions in which only one minijet hits the acceptance window. We further study the angular pattern of
the transverse-energy flow generated by semihard degrees of freedom at the early stage of high-energy nuclear collisions and
its dependence on the number of semihard collisions in the models either including or neglecting soft contributions to the
inelastic cross section at RHIC and LHC energies, as well as on the choice of infrared cutoff.
From Yadernaya Fizika, Vol. 65, No. 5, 2002, pp. 918–929.
Original English Text Copyright ? 2002 by Leonidov, Ostrovsky.
This article was submitted by the authors in English. 相似文献
9.
G. Moortgat-Pick H. Fraas 《The European Physical Journal C - Particles and Fields》2002,25(2):189-197
The consequences of CP and CPT invariance for production and subsequent decay of Dirac and Majorana fermions in polarized fermion-antifermion annihilation
are analytically studied. We derive general symmetry relations for the production spin density matrix and for the three-particle
decay matrices and obtain constraints for the polarization and the spin-spin correlations of Dirac and Majorana fermions.
We prove that only for Majorana fermions the energy and opening angle distribution factorizes exactly into contributions from
production and decay if CP is conserved.
Received: 6 November 2001 / Revised version: 23 April 2002 / Published online: 12 July 2002 相似文献
10.
A. Türler 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):271-274
In the past ten years, nuclear chemists have made considerable progress in developing fast on-line separation techniques,
which allowed to chemically characterize the first four transactinide elements Rf (rutherfordium, Z = 104), Db (dubnium, Z = 105), Sg (seaborgium, Z = 106), and recently also Bh (bohrium, Z = 107). In all cases the isolated nuclides were unambiguously identified by observing genetically linked decay chains. Nuclides
with production cross-sections of less than 100 pb and half-lives as short as a few seconds have been chemically isolated.
Thus, chemists have discovered or significantly contributed to the characterization of the nuclear-decay properties of a number
of transactinide nuclei. New techniques with greatly improved overall efficiencies should allow chemists to extend their studies
to even heavier elements such as Hs (hassium, Z = 108) and to the recently discovered superheavy elements with Z = 112 and 114, which can be produced only with picobarn cross-sections.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: andreas.tuerler@psi.ch 相似文献
11.
A.D. Martin R.G. Roberts W.J. Stirling R.S. Thorne 《The European Physical Journal C - Particles and Fields》2000,14(1):133-145
W and Z bosons will be produced copiously at the LHC proton-proton collider. We study the parton distribution dependence of the total
production cross sections and rapidity distributions, paying particular attention to the uncertainties arising from uncertainties
in the parton distributions themselves. Variations in the gluon, the strong coupling, the sea quarks and the overall normalisation
are shown to lead to small but non-negligible variations in the cross section predictions. Ultimately, therefore, the measurement
of these cross sections will provide a powerful cross check on our knowledge of parton distributions and their evolution.
Received: 23 November 1999 / Published online: 6 April 2000 相似文献
12.
A.V. Leonidov D.M. Ostrovsky 《The European Physical Journal C - Particles and Fields》2000,16(4):683-693
The azimuthal asymmetry of a minijet system produced at the early stage of nucleon–nucleon and nuclear collisions in a central
rapidity window is studied. We show that in pp collisions the minijet transverse energy production in a central rapidity window is essentially unbalanced in the azimuth
due to asymmetric contributions in which only one minijet hits the acceptance window. We further study the angular pattern
of the transverse energy flow generated by the semihard degrees of freedom at the early stage of high energy nuclear collisions
and its dependence on the number of semihard collisions in the models both including and neglecting soft contributions to
the inelastic cross section at RHIC and LHC energies as well as on the choice of the infrared cutoff.
Received: 19 January 1999 / Revised version: 18 February 2000 / Published online: 26 July 2000 相似文献
13.
A. De Roeck V.A. Khoze A.D. Martin R. Orava M.G. Ryskin 《The European Physical Journal C - Particles and Fields》2002,25(3):391-403
We summarize the possible processes which may be used to search for a Higgs boson, of mass in the range 114-130 GeV, at the
LHC. We discuss, in detail, two processes with rapidity gaps: exclusive Higgs production with tagged outgoing protons and
production by Weak Boson Fusion, in each case taking as the signal. We make an extensive study of all possible backgrounds, and discuss the relevant experimental issues. We emphasize the special features of these signals, and of their
background processes, and show that they could play an important role in identifying a light Higgs boson at the LHC.
Received: 5 July 2002 / Published online: 30 August 2002 相似文献
14.
The cross-sections for the reactions of muonium (anti-muonium) production in the high-energy electron (positron) scattering
by nuclei e
-(e
+) + Z↦Z + M
0(ˉM) + μ-(μ+) are calculated in dependence on energy and polarization of the initial electron (positron) and polarization of the final
μ-(μ+)-meson. Since this is a coherent phenomenon the cross-sections are proportional to Z2. For Z ∼ 100, due to the factor Z2, the cross-sections are large enough to be measured at the energies available for the HERA Collider at DESY. The results
are discussed in connection with a test of CPT invariance.
Received: 24 September 2002 / Accepted: 12 March 2003 / Published online: 27 May 2003 相似文献
15.
E. Roeckl 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):139-144
This review focusses on recent results obtained by using fusion-evaporation reactions for the production of N ≃ Z nuclei, the on-line mass separator of GSI for the preparation of the radioactive samples, and charged-particle and γ-ray
detectors for performing decay spectroscopy. The experimental results on prompt and β-delayed disintegration modes are discussed
in comparison with theoretical model predictions.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: e.roeckl@gsi.de 相似文献
16.
V.A. Khoze A.D. Martin M.G. Ryskin 《The European Physical Journal C - Particles and Fields》2001,21(1):99-103
We show that the broad transverse momentum distribution of the Higgs boson produced by WW fusion can provide a viable way to identify decays at the LHC, if particular kinematical configurations with large rapidity gaps are selected. We estimate the event
rate of the signal and of the QCD background. We also discuss Higgs boson detection via the and decay modes.
Received: 25 April 2001 / Published online: 29 June 2001 相似文献
17.
18.
H. Naik R.J. Singh R.H. Iyer 《The European Physical Journal A - Hadrons and Nuclei》2003,16(4):495-507
Charge distribution studies for heavy-mass fission products were carried out in the fast-neutron-induced fission of 232Th, 238U, 240Pu and 244Cm using radiochemical and gamma-ray spectrometric techniques. The width parameter( σZ/σA), the most probable charge/mass ( Z
P/A
P), the charge polarization (ΔZ) and the slope of charge polarization [ δ(ΔZ)/δA
′] as a function of the fragment mass (A
′) were deduced. The average charge dispersion parameter ( 〈σZ〉) and proton odd-even effect ( δp) were also obtained for these fissioning systems. The 〈σZ〉 and δp values in the fissioning systems 241Pu * and 245Cm * were determined for the first time. The δ(ΔZ)/δA
′ value is also determined for the first time in the fissioning systems 239U * , 241Pu * and 245Cm * . These data along with the literature data for even-Z fissioning systems such as 230Th * , 232Th * , 233U * , 234U * , 236U * , 238U * , 239Pu * , 240Pu*, 242Pu * , 246Cm * , 250Cf * and 252Cf(SF) are discussed in terms of nuclear structure effect and dynamics of descent from the saddle to the scission point. The
role of the excitation energy in low-energy fission is also discussed.
Received: 26 July 2002 / Accepted: 3 December 2002 / Published online: 3 April 2003
RID="a"
ID="a"Present address: Emeritus Scientist (CSIR) Bhabha Atomic Research Centre, Nuclear Recycle Group, WIP Building, Trombay, Mumbai-400085, India;
e-mail: rhiyer@magnum. barc.ernet.in
Communicated by D. Schwalm 相似文献
19.
M. Bender T. Cornelius G.A. Lalazissis J.A. Maruhn W. Nazarewicz P.-G. Reinhard 《The European Physical Journal A - Hadrons and Nuclei》2002,14(1):23-28
Recent mass measurements show a substantial weakening of the binding-energy difference δ2p(Z, N) = E(Z - 2, N) - 2E(Z, N) + E(Z + 2, N) in the neutron-deficient Pb isotopes. As δ2p is often attributed to the size of the proton magic gap, it might be speculated that reduction in δ2p is related to a weakening of the spherical Z = 82 shell. We demonstrate that the observed trend is described quantitatively by self-consistent mean-field models in terms
of deformed ground states of Hg and Po isotopes.
Received: 25 October 2001 / Accepted: 28 February 2002 相似文献
20.
The configuration-dependent cranked Nilsson-Strutinsky approach has been employed to study the properties and band structures
at high spin in the Z = N odd-odd nuclei 46V and 50Mn. The observed bands are explained and terminating states are confirmed by the calculations. The calculated and observed
bands are in good agreement without normalization, especially for terminating states. Possible bands with rotation around
the intermediate axis and the effect of γ-deformation on the total energy of several interesting configurations are discussed.
Received: 2 April 2002 / Accepted: 27 January 2003 / Published online: 15 April 2003 相似文献