Heavy quark results from STAR

I report the most recent measurements on open heavy flavor production at RHIC on behalf of the STAR collaboration. The total charm production cross section in midrapidity at RHIC energy is found to approximately scale by number of binary collisions in d + Au, Cu + Cu and Au + Au collisions. The nuclear modification factor of non-photonic electrons is strongly suppressed in central Au + Au collisions, suggesting substantial heavy quark energy loss at RHIC. The bottom decay contribution to non-photonic electrons was studied via the e–h and e–D ⁰ azimuthal angular correlations. The bottom contribution is found to be important at p _T >5 GeV/c, and is consistent with the FONLL calculation within uncertainties. Charm production through gluon jet splitting was measured by studying the D ^*± contents in the fully reconstructed jets in p+p collisions. This rate is consistent with pQCD evaluation of gluon splitting into a pair of charm quarks and subsequent hadronization.     

An optical lattice clock with spin-polarized 87Sr atoms

We present a new evaluation of an ⁸⁷Sr optical lattice clock using spin polarized atoms. The frequency of the ¹S₀→³P₀ clock transition is found to be 429 228 004 229 873.6 Hz with a fractional uncertainty of 2.6×10^-15, a value that is comparable to the frequency difference between the various primary standards throughout the world. This measurement is in excellent agreement with a previous one of similar accuracy [Phys. Rev. Lett. 98, 083002 (2007)].     

Charge radius change in the heavy tin isotopes until A = 132 from laser spectroscopy

Laser spectroscopy measurements have been carried out on the very neutron-rich tin isotopes with the COMPLIS experimental setup. Using the 5s ²5p ²³ P ₀ → 5s ²5p6s ³ P ₁ optical transition, hyperfine spectra of ^126-132Sn and ^{125m, 127m, 129m-131m}Sn where recorded for the first time. The variation of the mean-square charge radius ( δ〈r ²〉) between these nuclei and nuclear moments of the isomers and the odd isotopes were thus measured. An odd-even staggering which inverts at A = 130 is clearly observed. This indicates a small appearance of a plateau on the δ〈r ²〉 which has to be confirmed by measuring the isotope shift beyond A = 132. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: leblanc@ipno.in2p3.fr     

Absolute frequency measurement and high resolution spectroscopy of In 5sS0-5s5p P0 narrowline transition

We measure the frequency of the 5s²¹S₀-5s5p ³P₀ narrowline clock transition at 236.5 nm, for a single, trapped and laser cooled ¹¹⁵In⁺ ion. In the experiment, an ultra-narrow linewidth laser (<1.34 Hz at 3 s integration time) is used to interrogate the clock transition for high resolution spectroscopy. A linewidth of 43 Hz of the clock transition is observed. The uncertainty of the line centroid is 18 Hz, leading to a fractional uncertainty of 1.4×10^-14. The frequency is measured by using an optical frequency comb referenced to a cesium clock. The transition frequency is found to be 1, 267, 402, 452, 901.265 (256) kHz, averaged over 13 days of separate measurement. The accuracy of 2.35×10^-13 is due to the reference cesium clock calibrated against UTC time. We discuss ways for further improvements.     

Degenerate four-wave mixing diagnostics on OH and NH radicals in flames

Degenerate four wave mixing (DFWM) is applied as a diagnostic to study OH and NH radicals in flames. DFWM is a coherent technique which offers the advantages of a highly collimated signal beam permitting efficient rejection of interfering radiation and requiring minimal optical access. Rotational temperatures have been determined from the DFWM spectra and are in close agreement with the temperatures measured using coherent anti-Stokes Raman scattering of nitrogen.Work performed at the Combustion Research Facility, Sandia National Laboratories, supported by the U.S. Department of Energy, Energy Conversion and Utilization Technologies Program and Office of Basic Energy Sciences, Division of Chemical Sciences     

Band gaps and charge distribution in quasi-binary (GaSb) (InAs) crystals

Pseudopotential investigation of energy band gaps and charge distribution in quasi-binary (GaSb)_1-x(InAs)_x crystals has been reported. To the best of our knowledge, there had been no reported theoretical work on these materials. In agreement with experiment, the quasi-binary crystals of interest showed a significant narrowing of the optical band gap compared to the conventional Ga_xIn_1-xAs_ySb_1-y quaternary alloys (with x = 1 - y). Moreover, the absorption at the optical gaps indicated that (GaSb)_1-x(InAs)_x is a direct Γ to Γ band-gap semiconductor within a whole range of the x composition. The information derived from the present study predicts that the band gaps cross very important technological spectral regions and could be useful for thermophotovoltaic applications. Received 30 August 2002 Published online 1st April 2003 RID="a" ID="a"Present address: Physics Department, University of M'sila, 28000 M'sila, Algeria e-mail: N_Bouarissa@yahoo.fr     

Intracavity spectroscopy with modulated multimode lasers

The output of a cw multimode dye laser with an intracavity narrow-band absorber and its pump power modulated shows spectral condensation on both wings of the absorption line. This indicates phase locking of two groups of laser modes. The dispersion of the absorber modifies the mode spacing of the laser such that mode groups on both sides of the absorption line get into resonance with the modulation. These mode groups feel smaller loss and acquire the total laser power. Spectra of the laser output reveal the total absorption coefficient, the homogeneous broadening of the absorber, and the spectral width of individual laser modes.On leave from Lebedev Physical Institute, Academy of Sciences of the USSR, SU-117924 Moscow, USSR     

Raman heterodyne Ramsey spectroscopy in a Samarium atomic beam

A novel optical heterodyne technique for Raman Ramsey spectroscopy of atomic radio-frequency resonances in an atomic beam is reported. The method relies on coherent resonance Raman transitions to optically excite and probe sublevel coherence in atomic ground states using two separated atom-field interaction regions. First experimental results obtained with the use of Zeeman sublevels in the Samarium =570.68 nm (J=1)–(J=0) transition are discussed.     

Second-order isotope shifts in the ground configuration of Nd I

The isotope shift between all stable neodymium isotopes has been measured for 21 transitions in the Nd I spectrum by means of laser-atomic-beam absorption spectroscopy. A parametric analysis of the observed shifts in all the levels of the terms⁵ I,⁵ F, and⁵ S of the ground configuration 4f ⁴6s ² yields not only the magnetic parameterz _4f but, for the first time, also the effective electrostatic parametersa,b, andc. A more accurate value of the nuclear parameter ^148,150 (Nd)=0.369(20) fm² is obtained from the investigation of a 4f ³5d6s ²–4f ³5d6s6p transition. The comparison of non-relativistic Hartree-Fock calculations with the experimental data yields a scaling factorS _I ^* (Nd)=1.50(9) that agrees with the corresponding one from the hyperfine structure analysis.     

Partial charge-changing cross sections for neutron-deficient isotopes from58Ni fragmentation

At the projectile-fragment separator FRS of GSI, relativistic secondary beams of about 520 MeV/nucleon were produced by fragmentation of a primary beam of⁵⁸Ni at 650 MeV/nucleon in a beryllium target. By means of aE—B—TOF measurement, the fragments were identified and their charge-changing probabilities in targets of (CH₂) _n , C, Al, and Pb placed at the exit of the FRS were determined. Whereas a first article dealt with the total charge-changing cross sections, we describe in this second article the element distributions of these secondary fragments, which are found to depend strongly on the isospin of the secondary projectile as well as on the target material. In the case of the lead target, the influence of the electromagnetic dissociation is clearly visible in the one-proton and two-proton removal channels. The preference for the formation of even-Z fragments is much more pronounced for exotic secondary projectiles than for projectiles close to stability. Calculations with a geometrical abrasion-ablation model allow to understand the global features of the experimental data. However, far from stability, the discrepancies between calculations and experimental data increase.On leave of absence from Institute of Experimental Physics, University of Warsaw, PL-00-681 Warszawa, Hoa 69, Poland