In high-energy nuclear collisions, the conventional Glauber model is commonly used to evaluate the contribution to J/ψ suppression originating from the inelastic interaction with colorless bound nucleons. This requires an effective value
for the J/ψ-nucleon absorption cross-section which is larger than theoretically expected. On the other hand, multiple nucleon-nucleon
collisions, mediated by color exchange interactions, excite their color degrees of freedom. We investigate the importance
of this effect and find that these excited states provide a larger cross-section for J/ψ absorption. We conclude that the related corrections are important to explain the effective value extrapolated from experiment.
Received: 6 November 2000 / Accepted: 5 June 2001 相似文献
The role of electron correlation on different pairing symmetries are discussed in details where the electron correlation has
been treated within the slave boson formalism. It is shown that for a pure s or pure d wave pairing symmetry, the electronic
correlation suppresses the s wave gap magnitude (as well as the ) at a faster rate than that for the d wave gap. On the other hand, a complex order parameter of the form () shows anomalous temperature dependence. For example, if the temperature () at which the d wave component of the complex order parameter vanishes happens to be larger than that for the s wave component
(), then the growth of the d wave component is arrested with the onset of the s wave component of the order parameter. In this
mixed phase however, we find that the suppression in different components of the gap as well as the corresponding due to coulomb correlation are very sensitive to the relative pairing strengths of s and d channels as well as the underlying
lattice. Interestingly enough, in such a scenario (for a case of )the gap magnitude of the d wave component increases with electron correlation but not for certain values of electron correlation. However, this never happens in case of the s wave component. We also calculate
the temperature dependence of the superconducting gap along both the high symmetry directions ( and ) in a mixed symmetry pairing state and the thermal variation of the gap anisotropy [0pt][0pt] with electron correlation. The results
are discussed with reference to experimental observations.
Received: 26 August 1997 / Revised: 31 December 1997 /
Accepted: 28 January 1998 相似文献
Measurements at low transverse momentum will be performed at the LHC for studying particle production mechanisms in pp and heavy-ion collisions. Some of the experimental capabilities for bulk matter physics are presented, focusing on tracking
elements and particle identification. In order to anticipate the study of baryon production for both colliding systems at
multi-TeV energies, measurements for identified species and recent model extrapolations are discussed. Several mechanisms
are expected to compete for hadro-production in the low momentum region. For this reason, experimental observables that could
be used for investigating multi-parton interactions and help understanding the “underlying event” content in the first pp collisions at the LHC are also mentioned. 相似文献
In a hydrodynamic model, we have studied J/ψ production in Au+Au/Cu+Cu collisions at RHIC energy,
GeV. At the initial time, J/ψ’s are randomly distributed in the fluid. As the fluid evolves in time, the free streaming J/ψ’s are dissolved if the local fluid temperature exceeds a threshold temperature TJ/ψ. Sequential melting of charmonium states (χc, ψ′ and J/ψ), with melting temperatures
, TJ/ψ≈2Tc and feed-down fraction F≈0.3, explains the PHENIX data on the centrality dependence of J/ψ suppression in Au+Au collisions. J/ψpT spectra and the nuclear modification factor in Au+Au collisions are also well explained in the model. The model however overpredicts
the centrality dependence of J/ψ suppression in Cu+Cu collisions by 20–30%. The J/ψpT spectra are underpredicted by 20–30%. The model predicts that in central Pb+Pb collisions at LHC energy,
GeV, J/ψ’s are suppressed by a factor of ∼10. The model predicted a J/ψpT distribution in Pb+Pb collisions at LHC is similar to that in Au+Au collisions at RHIC. 相似文献
The current–voltage characteristics and photoresponse of mesa structured {111}‐oriented homoepitaxial CVD diamond p(i)n‐junctions with different intrinsic layer thickness are investigated. When a sufficiently thick intrinsic layer is present, a rectification ratio of 108 at ±10 V could be obtained. Good rectifying diodes show a high photoresponse ratio between 210 nm (above bandgap) and 500 nm (below bandgap), making them suitable for UV detection purposes. The results are compared with similar measurements carried out on polycrystalline CVD diamond pn‐junctions.
In many computer and server communications copper cables and wires are currently being used for data transmission and interconnects.
However, due to significant shortcomings, such as long transmission time, high noise level, unstable electrical properties,
and high power consumption for cooling, researchers are increasingly turning their research interests toward alternatives,
such as fiber optic interconnects and free-space optical communication technologies. In this paper, we present design considerations
for an integrated receiver for high-speed free-space line-of-sight optical interconnects for distortion-free data transmission
in an environment with mechanical vibrations and air turbulences. The receiver consists of an array of high-speed photodiodes
for data communication and an array of quadrant photodiodes for real-time beam tracking in order to compensate for the beam
misalignment caused by vibrations in servers. Different configurations for spatially positioning the quadrant and data photodiodes
are discussed for 4×4 and 9×9 multielement optical detector arrays. We also introduce a new beam tracking device, termed the
strip quadrant photodiodes, in order to accurately track highly focused optical beams with very small beam diameter. 相似文献
A simple model to describe the energetic phase diagram of electron-doped cuprate superconductor is developed. Interband pairing operates between the UHB and the defect states created by doping and supplied by both extincting HB-s. Two defect subbands correspond to the (π,0) and (π/2,π/2) momentum regions. Extended doping quenches the bare normal state gaps (pseudogaps). Maximal transition temperature corresponds to overlapping bands ensemble intersected by the chemical potential. Illustrative results for Tc, pseudo- and superconducting gaps are calculated on the whole doping scale. Major characteristic features on the phase diagram are reproduced. Anticipated manifestation of gaps doping dynamics is discussed. 相似文献