4,901 research outputs found
Glassiness in a model without energy barriers
We propose a microscopic model without energy barriers in order to explain
some generic features observed in structural glasses. The statics can be
exactly solved while the dynamics has been clarified using Monte Carlo
calculations. Although the model has no thermodynamic transition it captures
some of the essential features of real glasses, i.e., extremely slow
relaxation, time dependent hysteresis effects, anomalous increase of the
relaxation time and aging. This suggests that the effect of entropy barriers
can be an important ingredient to account for the behavior observed in real
glasses.Comment: 11 Pages + 3 Figures, Revtex, uufiles have been replaced since figure
2 was corrupted in the previous submissio
Spacings of Quarkonium Levels with the Same Principal Quantum Number
The spacings between bound-state levels of the Schr\"odinger equation with
the same principal quantum number but orbital angular momenta
differing by unity are found to be nearly equal for a wide range of power
potentials , with . Semiclassical approximations are in accord with this behavior. The
result is applied to estimates of masses for quarkonium levels which have not
yet been observed, including the 2P states and the 1D
states.Comment: 20 pages, latex, 3 uuencoded figures submitted separately (process
using psfig.sty
Charmonium states in QCD-inspired quark potential model using Gaussian expansion method
We investigate the mass spectrum and electromagnetic processes of charmonium
system with the nonperturbative treatment for the spin-dependent potentials,
comparing the pure scalar and scalar-vector mixing linear confining potentials.
It is revealed that the scalar-vector mixing confinement would be important for
reproducing the mass spectrum and decay widths, and therein the vector
component is predicted to be around 22%. With the state wave functions obtained
via the full-potential Hamiltonian, the long-standing discrepancy in M1
radiative transitions of and are alleviated
spontaneously. This work also intends to provide an inspection and suggestion
for the possible among the copious higher charmonium-like states.
Particularly, the newly observed X(4160) and X(4350) are found in the
charmonium family mass spectrum as MeV and MeV, which strongly favor the assignments
respectively. The corresponding radiative transitions, leptonic and two-photon
decay widths have been also predicted theoretically for the further
experimental search.Comment: 16 pages,3 figure
The CMS Tracker Readout Front End Driver
The Front End Driver, FED, is a 9U 400mm VME64x card designed for reading out
the Compact Muon Solenoid, CMS, silicon tracker signals transmitted by the
APV25 analogue pipeline Application Specific Integrated Circuits. The FED
receives the signals via 96 optical fibers at a total input rate of 3.4 GB/sec.
The signals are digitized and processed by applying algorithms for pedestal and
common mode noise subtraction. Algorithms that search for clusters of hits are
used to further reduce the input rate. Only the cluster data along with trigger
information of the event are transmitted to the CMS data acquisition system
using the S-LINK64 protocol at a maximum rate of 400 MB/sec. All data
processing algorithms on the FED are executed in large on-board Field
Programmable Gate Arrays. Results on the design, performance, testing and
quality control of the FED are presented and discussed
Monitoring the CMS strip tracker readout system
The CMS Silicon Strip Tracker at the LHC comprises a sensitive area of approximately 200 m2 and 10 million readout channels. Its data acquisition system is based around a custom analogue front-end chip. Both the control and the readout of the front-end electronics are performed by off-detector VME boards in the counting room, which digitise the raw event data and perform zero-suppression and formatting. The data acquisition system uses the CMS online software framework to configure, control and monitor the hardware components and steer the data acquisition. The first data analysis is performed online within the official CMS reconstruction framework, which provides many services, such as distributed analysis, access to geometry and conditions data, and a Data Quality Monitoring tool based on the online physics reconstruction. The data acquisition monitoring of the Strip Tracker uses both the data acquisition and the reconstruction software frameworks in order to provide real-time feedback to shifters on the operational state of the detector, archiving for later analysis and possibly trigger automatic recovery actions in case of errors. Here we review the proposed architecture of the monitoring system and we describe its software components, which are already in place, the various monitoring streams available, and our experiences of operating and monitoring a large-scale system
Fine structure splittings of excited P and D states in charmonium
It is shown that the fine structure splittings of the and
excited states in charmonium are as large as those of the state if the
same is used. The predicted mass
GeV appears to be 120 MeV lower that the center of gravity of the
multiplet and lies below the threshold. Our value of
is approximately 80 MeV lower than that from the paper by Godfrey and Isgur
while the differences in the other masses are \la 20 MeV. Relativistic
kinematics plays an important role in our analysis.Comment: 12 page
Commissioning and Calibrating the CMS Silicon Strip Tracker
The data acquisition system for the CMS Silicon Strip Tracker (SST) is based around a custom analogue front-end ASIC, an analogue optical link system and an off-detector VME board that performs digitization, zero-suppression and data formatting. A complex procedure is required to optimally configure, calibrate and synchronize the 107 channels of the SST readout system. We present an overview of this procedure, which will be used to commission and calibrate the SST during the integration, Start-Up and operational phases of the experiment. Recent experiences from the CMS Magnet Test Cosmic Challenge and system tests at the Tracker Integration Facility are also reported
Inherent Structures in models for fragile and strong glass
An analysis of the dynamics is performed, of exactly solvable models for
fragile and strong glasses, exploiting the partitioning of the free energy
landscape in inherent structures. The results are compared with the exact
solution of the dynamics, by employing the formulation of an effective
temperature used in literature. Also a new formulation is introduced, based
upon general statistical considerations, that performs better. Though the
considered models are conceptually simple there is no limit in which the
inherent structure approach is exact.Comment: 19 pages, 4 figure
Bohr-Sommerfeld quantization and meson spectroscopy
We use the Bohr-Sommerfeld quantization approach in the context of
constituent quark models. This method provides, for the Cornell potential,
analytical formulae for the energy spectra which closely approximate numerical
exact calculations performed with the Schrodinger or the spinless Salpeter
equations. The Bohr-Sommerfeld quantization procedure can also be used to
calculate other observables such as r.m.s. radius or wave function at the
origin. Asymptotic dependence of these observables on quantum numbers are also
obtained in the case of potentials which behave asymptotically as a power-law.
We discuss the constraints imposed by these formulae on the dynamics of the
quark-antiquark interaction.Comment: 13 page
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