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Search Results: 1 - 10 of 297443 matches for " J. Balewski "
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Measurement of Sivers Asymmetries for Di-jets in \sqrt{s}=200 GeV pp Collisions at STAR
J. Balewski
Physics , 2006, DOI: 10.1063/1.2750842
Abstract: Measurement of the transverse spin dependence of the di-jet opening angle in pp collisions at sqrt{s}=200 GeV has been performed by the STAR collaboration. An analyzing power consistent with zero has been observed over a broad range in pseudorapidity sum of the two jets with respect to the polarized beam direction. A non-zero (Sivers) correlation between transverse momentum direction of partons in the initial state and transverse spin orientation of the parent proton has been previously observed in semi-inclusive deep inelastic scattering (SIDIS). The present measurements are much smaller than deduced from predictions made for STAR di-jets based on non-zero quark Sivers functions deduced from SIDIS, and furthermore indicate that gluon Sivers asymmetries are comparably small.
Planck-Scale Gravity Test at PETRA  [PDF]
Vahagn Gharibyan, Klaus Balewski
Journal of Modern Physics (JMP) , 2016, DOI: 10.4236/jmp.2016.79088
Abstract: Quantum or torsion gravity models predict unusual properties of space-time at very short distances. In particular, near the Planck length, around 10-35 m, empty space may behave as a crystal, singly or doubly refractive. This hypothesis, however, remains uncheckable for any direct measurement since the smallest distance accessible in experiment is about 10-19 m at the LHC. Here we propose a laboratory test to measure space birefringence or refractivity induced by gravity. A sensitivity 10-31 m for doubly and 10-28 m for singly refractive vacuum could be reached with PETRA 6 GeV beam exploring UV laser Compton scattering.
F?rster interaction induced phase shift in a pair state interferometer
J. Nipper,J. B. Balewski,A. T. Krupp,S. Hofferberth,R. L?w,T. Pfau
Physics , 2012,
Abstract: We present experiments measuring an interaction induced phase shift of Rydberg atoms at Stark tuned F\"orster resonances. The phase shift features a dispersive shape around the resonance, showing that the interaction strength and sign can be tuned coherently. We use a pair state interferometer to measure the phase shift. Although the coupling between pair states is coherent on the time scale of the experiment, a loss of visibility occurs as a pair state interferometer involves three simultaneously interfering paths and only one of them is phase shifted by the mutual interaction. Despite additional dephasing mechanisms a pulsed F\"orster coupling sequence allows to observe coherent dynamics around the F\"orster resonance.
Highly resolved measurements of Stark-tuned F?rster resonances between Rydberg atoms
J. Nipper,J. B. Balewski,A. T. Krupp,B. Butscher,R. L?w,T. Pfau
Physics , 2012,
Abstract: We report on experiments exploring Stark-tuned F\"orster resonances between Rydberg atoms with unprecedented resolution in the F\"orster defect. The individual resonances are expected to exhibit different angular dependencies, opening the possibility to tune not only the interaction strength but also the angular dependence of the pair state potentials by an external electric field. We achieve a high resolution by optical Ramsey interferometry for Rydberg atoms combined with electric field pulses. The resonances are detected by a loss of visibility in the Ramsey fringes due to resonances in the interaction. We present measurements of the density dependence as well as of the coherence time at and close to F\"orster resonances.
Rydberg trimers and excited dimers bound by internal quantum reflection
V. Bendkowsky,B. Butscher,J. Nipper,J. Balewski,J. P. Shaffer,R. L?w,T. Pfau,W. Li,J. Stanojevic,T. Pohl,J. M. Rost
Physics , 2009, DOI: 10.1103/PhysRevLett.105.163201
Abstract: Quantum reflection is a pure wave phenomena that predicts reflection of a particle at a changing potential for cases where complete transmission occurs classically. For a chemical bond, we find that this effect can lead to non-classical vibrational turning points and bound states at extremely large interatomic distances. Only recently has the existence of such ultralong-range Rydberg molecules been demonstrated experimentally. Here, we identify a broad range of molecular lines, most of which are shown to originate from two different novel sources: a single-photon associated triatomic molecule formed by a Rydberg atom and two ground state atoms and a series of excited dimer states that are bound by a so far unexplored mechanism based on internal quantum reflection at a steep potential drop. The properties of the Rydberg molecules identified in this work qualify them as prototypes for a new type of chemistry at ultracold temperatures.
The Forward GEM Tracker of STAR at RHIC
F. Simon,J. Balewski,R. Fatemi,D. Hasell,J. Kelsey,R. Majka,B. Page,M. Plesko,D. Underwood,N. Smirnov,J. Sowinski,H. Spinka,B. Surrow,G. Visser
Physics , 2008,
Abstract: The STAR experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) is in the process of designing and constructing a forward tracking system based on triple GEM technology. This upgrade is necessary to give STAR the capability to reconstruct and identify the charge sign of W bosons over an extended rapidity range through their leptonic decay mode into an electron (positron) and a neutrino. This will allow a detailed study of the flavor-separated spin structure of the proton in polarized p + p collisions uniquely available at RHIC. The Forward GEM Tracker FGT will consist of six triple GEM disks with an outer radius of ~39 cm and an inner radius of ~10.5 cm, arranged along the beam pipe, covering the pseudo-rapidity range from 1.0 to 2.0 over a wide range of collision vertices. The GEM foils will be produced by Tech-Etch, Inc. Beam tests with test detectors using 10 cm x 10 cm Tech-Etch GEM foils and a two dimensional orthogonal strip readout have demonstrated a spatial resolution of 70 um or better and high efficiency.
Polarization Observables of pp -> pp pi0 Near Threshold
P. Thorngren Engblom,H. O. Meyer,J. T. Balewski,J. Doskow,R. E. Pollock,B. V. Przewoski,T. Rinckel,F. Sperisen,W. W. Daehnick,Swapan K. Saha,W. Haeberli,B. Lorentz,F. Rathmann,B. Schwartz,T. Wise,P. V. Pancella
Physics , 1998,
Abstract: With the aim to study spin dependence of pion production near threshold, an internal target facility and a forward detector have been installed in the Cooler synchrotron ring at IUCF. The detector system comprises scintillators and wire chambers. The target consists of a thin-walled open-ended storage cell into which polarized atomic hydrogen is injected. Using a stored and cooled, polarized proton beam, polarization observables of the reaction pp -> pp pi0 have been studied at energies between 21 and 55 MeV above the pion production threshold in the center of mass system. We report here measurements of the spin correlation parameters Axx and Ayy, and the analyzing power Ay, integrated over the pion polar angle.
Initial singlet and triplet spin state contributions to pp -> pp pi0
P. Thorngren Engblom,H. O. Meyer,J. T. Balewski,W. W. Daehnick,J. Doskow,W. Haeberli,B. Lorentz,P. V. Pancella,R. E. Pollock,B. von Przewoski F. Rathmann,T. Rinckel,Swapan K. Saha,B. Schwartz,A. Wellinghausen,T. Wise.
Physics , 1999, DOI: 10.1016/S0375-9474(99)00604-1
Abstract: The PINTEX facility at the IUCF Cooler ring, dedicated to the study of spin dependence in nucleon-nucleon interactions, has been used to measure polarization observables of the reaction pp -> pp pi0 at beam energies between 325 and 400 MeV. The stored polarized proton beam had spin projections both in the longitudinal and the transverse directions with respect to the beam momentum. We report here on the measurements of the relative transverse and longitudinal spin-dependent cross sections, deltasigma_T/sigma_tot and deltasigma_L/sigma_tot, and how from these observables the initial spin singlet and triplet cross sections are obtained. Considering angular momentum states less or equal to one, the contribution of the Ps partial waves to the cross section can be extracted.
Beam Profile Measurements and Simulations of the PETRA Laser-Wire
J. Carter,I. Agapov,G. A. Blair,G. Boorman,C. Driouichi,F. Poirier,M. T. Price,T. Kamps,K. Balewski,H. Lewin,S. Schreiber,K. Wittenburg,N. Delerue,D. F. Howell,S. T. Boogert,S. Malton
Physics , 2005,
Abstract: The Laser-wire will be an essential diagnostic tool at the International Linear Collider. It uses a finely focussed laser beam to measure the transverse profile of electron bunches by detecting the Compton-scattered photons (or degraded electrons) downstream of where the laser beam intersects the electron beam. Such a system has been installed at the PETRA storage ring at DESY, which uses a piezo-driven mirror to scan the laser-light across the electron beam. Lat- est results of experimental data taking are presented and compared to detailed simulations using the Geant4 based program BDSIM.
Spin Correlation Coefficients in pp-->pnpi+ from 325 to 400 MeV
Swapan K. Saha,W. W. Daehnick,R. W. Flammang,J. T. Balewski,H. O. Meyer,R. E. Pollock,B. v. Przewoski,T. Rinckel,P. Thorngren-Engblom,B. Lorentz,F. Rathmann,B. Schwartz,T. Wise,P. V. Pancella
Physics , 1999, DOI: 10.1016/S0370-2693(99)00845-X
Abstract: The spin correlation coefficient combinations Axx + Ayy, Axx - Ayy and the analyzing powers Ay(theta) were measured for pp-->pnpi+ at beam energies of 325, 350, 375 and 400 MeV. A polarized internal atomic hydrogen target and a stored, polarized proton beam were used. These polarization observables are sensitive to contributions of higher partial waves. A comparison with recent theoretical calculations is provided.
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