132 research outputs found
Time domain deBroglie wave interferometry along a magnetic guide
Time domain deBroglie wave interferometry [Cahn et al, Phys. Rev. Lett. 79,
784] is applied to Rb87 atoms in a magnetic guide. A standing wave light field
is carefully aligned along the guiding direction of the magnetic trapping
potential from a soft-ferromagnetic 4-foil structure. A sequence of two
standing wave pulses is applied to the magnetically trapped atoms. The
backscattered light at the atomic density grating revival time is collected and
detected via a heterodyning technique. In addition to the observed recoil
oscillations that fit the interferometer theory for atoms in free space, we
observe a decay of the interferometer contrast on a millisecond time scale with
unexpected millisecond-scale oscillations. We find that the oscillating decay
is explained by a residual variation of the linear trapping potential along the
standing wave direction.Comment: 22 pages, 7 figure
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
Parton distributions incorporating QED contributions
We perform a global parton analysis of deep inelastic and related hard-scattering data,
including O( QED) corrections to the parton evolution. Although the quality of the fit is
essentially unchanged, there are two important physical consequences. First, the different
DGLAP evolution of u and d type quarks introduces isospin violation, i.e. up 6= dn, which
is found to be unambiguously in the direction to reduce the NuTeV sin2 W anomaly.
A second consequence is the appearance of photon parton distributions
(x,Q2) of the
proton and the neutron. In principle these can be measured at HERA via the deep inelastic
scattering processes eN â e
X; our predictions are in agreement with the present data
Amicable pairs and aliquot cycles for elliptic curves
An amicable pair for an elliptic curve E/Q is a pair of primes (p,q) of good
reduction for E satisfying #E(F_p) = q and #E(F_q) = p. In this paper we study
elliptic amicable pairs and analogously defined longer elliptic aliquot cycles.
We show that there exist elliptic curves with arbitrarily long aliqout cycles,
but that CM elliptic curves (with j not 0) have no aliqout cycles of length
greater than two. We give conjectural formulas for the frequency of amicable
pairs. For CM curves, the derivation of precise conjectural formulas involves a
detailed analysis of the values of the Grossencharacter evaluated at a prime
ideal P in End(E) having the property that #E(F_P) is prime. This is especially
intricate for the family of curves with j = 0.Comment: 53 page
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
The Universal Kummer Threefold
The universal Kummer threefold is a 9-dimensional variety that represents the
total space of the 6-dimensional family of Kummer threefolds in 7-dimensional
projective space. We compute defining polynomials for three versions of this
family, over the Satake hypersurface, over the G\"opel variety, and over the
reflection representation of type E7. We develop classical themes such as theta
functions and Coble's quartic hypersurface using current tools from
combinatorics, geometry, and commutative algebra. Symbolic and numerical
computations for genus 3 moduli spaces appear alongside toric and tropical
methods.Comment: 50 pages; v2: added Remark 4.3, strengthened Lemma 8.3; v3: added
references and added supplementary files to sourc
Planck intermediate results I : Further validation of new Planck clusters with XMM-Newton
Peer reviewe
Planck Intermediate Results II: Comparison of SunyaevâZeldovich measurements from Planck and from the Arcminute Microkelvin Imager for 11 galaxy clusters
A comparison is presented of SunyaevâZeldovich measurements for 11 galaxy clusters as obtained by Planck and by the ground-based interferom- eter, the Arcminute Microkelvin Imager. Assuming a universal spherically-symmetric Generalised Navarro, Frenk & White (GNFW) model for the cluster gas pressure profile, we jointly constrain the integrated Compton-Y parameter (Y500) and the scale radius (Ξ500) of each cluster. Our resulting constraints in the Y500 â Ξ500 2D parameter space derived from the two instruments overlap significantly for eight of the clusters, although, overall, there is a tendency for AMI to find the SunyaevâZeldovich signal to be smaller in angular size and fainter than Planck. Significant discrepancies exist for the three remaining clusters in the sample, namely A1413, A1914, and the newly-discovered Planck cluster PLCKESZ G139.59+24.18. The robustness of the analysis of both the Planck and AMI data is demonstrated through the use of detailed simulations, which also discount confusion from residual point (radio) sources and from diffuse astrophysical foregrounds as possible explanations for the discrepancies found. For a subset of our cluster sample, we have investigated the dependence of our results on the assumed pressure profile by repeating the analysis adopting the best-fitting GNFW profile shape which best matches X-ray observations. Adopting the best-fitting profile shape from the X-ray data does not, in general, resolve the discrepancies found in this subset of five clusters. Though based on a small sample, our results suggest that the adopted GNFW model may not be sufficiently flexible to describe clusters universally
- âŠ