7,405,692 research outputs found
Hard scattering and jets--from p-p collisions in the 1970's to Au+Au collisions at RHIC
Hard scattering in p-p collisions, discovered at the CERN ISR in 1972 by the
method of leading particles, proved that the partons of Deeply Inelastic
Scattering strongly interacted with each other. Further ISR measurements
utilizing inclusive single or pairs of hadrons established that high pT
particles are produced from states with two roughly back-to-back jets which are
the result of scattering of constituents of the nucleons as described by
Quantum Chromodynamics (QCD), which was developed during the course of these
measurements. These techniques, which are the only practical method to study
hard-scattering and jet phenomena in Au+Au central collisions, are reviewed,
with application to measurements at RHIC.Comment: 4 pages, 5 figures, Proceedings of Hard Probes 2004, International
Conference on Hard and Electromagnetic Probes of High Energy Nuclear
Collisions, Nov 4-10, 2004, to appear in EPJ
Creating Ioffe-Pritchard micro-traps from permanent magnetic film with in-plane magnetization
We present designs for Ioffe-Pritchard type magnetic traps using planar
patterns of hard magnetic material. Two samples with different pattern designs
were produced by spark erosion of 40 m thick FePt foil. The pattern on the
first sample yields calculated axial and radial trap frequencies of 51 Hz and
6.8 kHz, respectively. For the second sample the calculated frequencies are 34
Hz and 11 kHz. The structures were used successfully as a magneto-optical trap
for Rb and loaded as a magnetic trap. A third design, based on
lithographically patterned 250 nm thick FePt film on a Si substrate, yields an
array of 19 traps with calculated axial and radial trap frequencies of 1.5 kHz
and 110 kHz, respectively.Comment: 8 pages, 5 figures Revised and accepted for EPJD, improved picture
Phenomenology of the SU(3)_c X SU(3)_L X U(1)_X model with right-handed neutrinos
A phenomenological analysis of the three-family local gauge group
with right-handed neutrinos is carried
out. Instead of using the minimal scalar sector able to break the symmetry in a
proper way, we introduce an alternative set of four Higgs scalar triplets,
which combined with an anomaly-free discrete symmetry, produces a quark mass
spectrum without hierarchies in the Yukawa coupling contants. We also embed the
structure into a simple gauge group and show some conditions to achieve a low
energy gauge coupling unification, avoiding possible conflict with proton decay
bounds. By using experimental results from the CERN-LEP, SLAC linear collider
and atomic parity violation data, we update constraints on several parameters
of the model.Comment: RevTeX, 10 pages, 4 figures. v2: 13 pages. Substantial changes. New
section about RGE analysis. Experimental data updated. v3: Discussions about
bounds from unitarity violation of the CKM matrix and from FCNC included.
Accepted for publication in Eur. Phys. J.
Melting and evaporation transitions in small Al clusters: canonical Monte-Carlo simulations
A dimer of bound atoms cannot melt, only dissociate. Bulk metals show a well
defined first order transition between their solid and liquid phases. The
appearance of the melting transition is explored for increasing clusters sizes
via the signatures in the specific heat and the root mean square of the bond
lengths (Berry parameter) by means of Monte-Carlo simulations
of Al clusters modelled by Gupta potentials. Clear signatures of a melting
transition appear for atoms. Closed-shell effects are shown for
clusters with up to 56 atoms. The melting transition is compared in detail with
the dissociation transition, which induces a second and possibly much larger
local maximum in the specific heat at higher temperatures. Larger clusters are
shown to fragment into dimers and trimers, which in turn dissociate at higher
temperatures.Comment: 6 pages, 7 figure
Accurate spectroscopy of Sr atoms
We report the frequency measurement with an accuracy in the 100 kHz range of
several optical transitions of atomic Sr : at 689 nm, at 688 nm and at 679 nm. Measurements are performed with
a frequency chain based on a femtosecond laser referenced to primary frequency
standards. They allowed the indirect determination with a 70 kHz uncertainty of
the frequency of the doubly forbidden 5s^2^1S_0- 5s5p^3P_0 transition of
Sr at 698 nm and in a second step its direct observation. Frequency
measurements are performed for Sr and Sr, allowing the
determination of , and isotope shifts, as well as the
hyperfine constants.Comment: 12 pages, 16 figure
Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV
We report the first measurement of charged particle elliptic flow in Pb-Pb
collisions at 2.76 TeV with the ALICE detector at the CERN Large Hadron
Collider. The measurement is performed in the central pseudorapidity region
(||<0.8) and transverse momentum range 0.2< < 5.0 GeV/. The
elliptic flow signal v, measured using the 4-particle correlation method,
averaged over transverse momentum and pseudorapidity is 0.087 0.002
(stat) 0.004 (syst) in the 40-50% centrality class. The differential
elliptic flow v reaches a maximum of 0.2 near = 3
GeV/. Compared to RHIC Au-Au collisions at 200 GeV, the elliptic flow
increases by about 30%. Some hydrodynamic model predictions which include
viscous corrections are in agreement with the observed increase.Comment: 10 pages, 4 captioned figures, published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/389
Probing dense and hot matter with low-mass dileptons and photons
Results on low-mass dileptons, covering the very broad energy range from the
BEVALAC up to SPS are reviewed. The emphasis is on the open questions raised by
the intriguing results obtained so far and the prospects for addressing them in
the near future with the second generation of experiments, in particular HADES,
NA60 and PHENIX.Comment: 6 pages, 8 figures, Proceedings of Hard Probes 2004 Conference,
Ericeira, November 4-10, 2004. Caption of Figure 2 corrected. To be published
in Eur. Phys. J. C. The orginal version is available at www.springerlink.co
Near-threshold production of omega mesons in the pn -> d omega reaction
The first measurement of the p n -> d omega total cross section has been
achieved at mean excess energies of Q = 28 and 57 MeV by using a deuterium
cluster-jet target. The momentum of the fast deuteron was measured in the ANKE
spectrometer at COSY-Juelich and that of the slow "spectator" proton p(sp) from
the p d -> p(sp) d omega reaction in a silicon telescope placed close to the
target. The cross sections lie above those measured for p p -> p p omega but
seem to be below theoretical predictions.Comment: 7 pages, 8 figures; second approach to describe the background has
been added; results changed insignificantly, EPJ in pres
Absolute resonance strengths in the 6,7Li(alpha,gamma)10,11B reactions
The absolute strengths of the Ea=1175keV resonance in the 6Li(a,g)10B
reaction and of the Ea=814 keV resonance in the 7Li(a,g)11B reaction have been
measured to =366+-38 meV and =300+-32 meV,
respectively, in good agreement with previous values.
These resonances can be used to measure the absolute acceptance of the recoil
separator ERNA to a precision of about 10%.Comment: 6 pages, 5 figures, to appear in European Physical Journal
Circular 79
The development of improved cultivars of barley is accomplished through comprehensive
plant breeding programs. Such programs:
1). evaluate genetically-diverse germplasm in order to identify superiorperforming
genotypes;
2). create new genetic recombinations from crosses or other means using selected
parental genotypes;
3). evaluate segregating progeny from these families while exerting selection
pressure for desirable characteristics; and
4). identify superior-performing cultivars in yield trials conducted at multiple
locations over years.
This circular documents the current status of research in cultivar development
associated with the Alaska barley breeding program
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