P. D. Barnes
A5016753083- Particle accelerators and beam dynamics
- High-Energy Particle Collisions Research
- Particle Accelerators and Free-Electron Lasers
- Particle physics theoretical and experimental studies
- Superconducting Materials and Applications
- Quantum Chromodynamics and Particle Interactions
- Gyrotron and Vacuum Electronics Research
- Dark Matter and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Particle Detector Development and Performance
- Radio Frequency Integrated Circuit Design
- Nuclear reactor physics and engineering
- Physics of Superconductivity and Magnetism
- Nuclear Physics and Applications
- Magnetic confinement fusion research
- Nuclear physics research studies
- Radiation Detection and Scintillator Technologies
- Electron and X-Ray Spectroscopy Techniques
- Copper Interconnects and Reliability
- Electromagnetic Compatibility and Noise Suppression
- Relativity and Gravitational Theory
- Advanced Electron Microscopy Techniques and Applications
- Quantum Mechanics and Applications
- Scientific Computing and Data Management
- Computational Physics and Python Applications
University of Michigan–Ann Arbor
2020-2023
Los Alamos National Laboratory
1997-2019
Ithaca College
2007
Cornell University
2002-2006
Tokyo University of Science
2005
PHENIX laboratory
2005
Banaras Hindu University
2005
China Institute of Atomic Energy
2005
Abilene Christian University
2005
Institute of Particle Physics
2005
Bose-Einstein correlations of identically charged pion pairs were measured by the PHENIX experiment at mid-rapidity in Au+Au collisions $\sqrt{s_{\rm NN}}$ = 200 GeV. The Bertsch-Pratt radius parameters determined as a function transverse momentum pair and centrality collision. Using \it{full} Coulomb correction, ratio $R_{\rm out}/R_{\rm side}$ is smaller than unity for $<k_{\rm T}>$ from 0.25 to 1.2 GeV/c all centralities. However, using recently developed partial correction methods, we...
Transverse single-spin asymmetries to probe the transverse-spin structure of proton have been measured for neutral pions and nonidentified charged hadrons from polarized proton-proton collisions at midrapidity s=200 GeV. The data cover a transverse momentum (pT) range 1.0–5.0 GeV/c 0.5–5.0 hadrons, Feynman-x value approximately zero. seen in this previously unexplored kinematic region are consistent with zero within errors few percent. In addition, inclusive hadron cross section 0.5<pT<7.0...
Differential elliptic flow (${v}_{2}$) for $\ensuremath{\phi}$ mesons and (anti)deuterons $(\overline{d})d$ is measured $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=200\text{ }\text{ }\mathrm{GeV}$. The ${v}_{2}$ follows the trend of lighter ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ ${K}^{\ifmmode\pm\else\textpm\fi{}}$ mesons, suggesting that ordinary hadrons interacting with standard hadronic cross sections are not primary driver development. values suggest additive...
We report the measurement of transverse momentum dependence inclusive $J/\ensuremath{\psi}$ polarization in $p+p$ collisions at $\sqrt{s}=200\text{ }\text{ }\mathrm{GeV}$ performed by PHENIX Experiment Relativistic Heavy Ion Collider. The is studied helicity, Gottfried-Jackson, and Collins-Soper frames for ${p}_{T}<5\text{ }\mathrm{GeV}/c$ $|y|<0.35$. helicity Gottfried-Jackson consistent with zero all momenta, a slight (1.8 sigma) trend towards longitudinal momenta above $2\text{...
The standard model (SM) of particle physics is spectacularly successful, yet the measured value muon anomalous magnetic moment ${(g\ensuremath{-}2)}_{\ensuremath{\mu}}$ deviates from SM calculations by $3.6\ensuremath{\sigma}.$ Several theoretical models attribute this to existence a ``dark photon,'' an additional U(1) gauge boson, which weakly coupled ordinary photons. PHENIX experiment at Relativistic Heavy Ion Collider has searched for dark photon, $U$, in...
The PHENIX collaboration presents first measurements of low-momentum ($0.4<{p}_{T}<3\text{ }\text{ }\mathrm{GeV}/c$) direct-photon yields from $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=39$ and 62.4 GeV. For both beam energies the are substantially enhanced with respect to expectations prompt processes, similar observed in $\sqrt{{s}_{NN}}=200$. Analyzing photon yield as a function experimental observable $d{N}_{\mathrm{ch}}/d\ensuremath{\eta}$ reveals that ($>1\text{...
If the Peccei-Quinn field containing QCD axion undergoes rotations in early universe, dimension-five operator responsible for neutrino masses can generate a lepton asymmetry that ultimately gives rise to observed baryon of Universe. This lepto-axiogenesis scenario requires flat potential radial direction field, naturally realized supersymmetric models. We carefully compute efficiency this mechanism Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) and Kim-Shifman-Vainshtein-Zakharov (KSVZ) models...
New measurements are presented for charged hadron azimuthal correlations at midrapidity in Au+Au collisions (square root)s(NN) = 62.4 and 200 GeV. They compared to earlier obtained 130 GeV Pb + 17.2 Sizeable anisotropies observed with centrality transverse momentum (pT) dependence characteristic of elliptic flow (upsilon2). For a broad range centralities, the magnitudes trends differential anisotropy, upsilon2(pT), change very little over collision energy 62-200 GeV, indicating saturation...
The invariant differential cross section for inclusive electron production in $p+p$ collisions at $\sqrt{s}=200\text{ }\text{ }\mathrm{GeV}$ has been measured by the PHENIX experiment BNL Relativistic Heavy Ion Collider over transverse momentum range $0.4\ensuremath{\le}{p}_{T}\ensuremath{\le}5.0\text{ }\mathrm{GeV}/c$ central rapidity region ($|\ensuremath{\eta}|\ensuremath{\le}0.35$). contribution to spectrum from semileptonic decays of hadrons carrying heavy flavor, i.e., charm quarks or,...
We report the first measurement of transverse single-spin asymmetries in J/ψ production from transversely polarized p+p collisions at s=200 GeV with data taken by PHENIX experiment 2006 and 2008. The was performed over rapidity ranges 1.2<|y|<2.2 |y|<0.35 for momenta up to 6 GeV/c. Relativistic Heavy Ion Collider is dominated processes involving initial-state gluons, can provide access gluon dynamics within nucleon. Such may also shed light on long-standing question QCD mechanism....
To achieve luminosities of 30-100 times CESR, 1-2 A current must be stored. CESR B-factory parameter list calls for 50 MV two rings, to supplied by 16 cells operating at 10 MV/m gradient. With a new cell shape, the impedances dangerous higher order modes (HOM) are drastically reduced. All HOMs propagate out cavity via beam pipe, which is specially shaped. This allows HOM power couplers placed completely outside cryostat. ferrite absorber on pipe lowers all Qs approximately 100, sufficient...
We report a measurement of $e^+e^-$ pairs from semileptonic heavy-flavor decays in $p$+$p$ collisions at $\sqrt{s_{NN}}=200$~GeV. The pair yield $b\bar{b}$ and $c\bar{c}$ is separated by exploiting double differential fit done simultaneously dielectron invariant mass $p_T$. used three different event generators, {\sc pythia}, mc@nlo}, powheg}, to simulate the spectra production. data can be well described all generators within detector acceptance. However, when using extrapolate $4\pi$,...
We study lepto-axiogenesis in theories where the right-handed neutrino is light enough that its dynamics affect determination of baryon asymmetry. When compared with high-scale Majorana mass may be treated as an effective dimension-five operator, we find predicted saxion lower. Two distinct scenarios emerge. In first, processes generate asymmetry are equilibrium down to neutrino. second, relevant never reach equilibrium; number freezes in. comment on implications for supersymmetric spectra...
The standard model (SM) of particle physics is spectacularly successful, yet the measured value muon anomalous magnetic moment $(g-2)_\mu$ deviates from SM calculations by 3.6$\sigma$. Several theoretical models attribute this to existence a "dark photon," an additional U(1) gauge boson, which weakly coupled ordinary photons. PHENIX experiment at Relativistic Heavy Ion Collider has searched for dark photon, $U$, in $\pi^0,\eta \rightarrow \gamma e^+e^-$ decays and obtained upper limits...
A hidden sector that kinetically mixes with the minimal supersymmetric standard model provides simple and well-motivated dark matter candidates possess many of properties a traditional weakly interacting massive particle (WIMP). These constructions can also provide natural explanation for why is at weak scale even if it resides in sector. In sector, pattern symmetry breaking generally makes particles their superpartners lie around same mass scale, opening novel possibilities variety...
Weak-scale secluded sector dark matter can reproduce the observed relic density with thermal freeze-out within that sector. If nature is supersymmetric, three portals to visible - a gauge portal, Higgs and gaugino portal are present. We present gamma ray spectra relevant for indirect detection of annihilation in such setups. Since symmetries stabilize matter, $R$-parity unnecessary, we investigate impact violation on spectra. limits from Fermi Large Area Telescope observations dwarf galaxies...
Six 1300 MHz superconducting niobium 2-cell cavities are manufactured in-house for the prototype of Cornell ERL injector to boost energy a high current, low emittance beam produced by DC gun. Designed current acceleration, these have new characteristics as compared previously developed low-current such those TTF Precision manufacture is emphasized better straightness cavity axis so avoid unwanted dilution. We present manufacturing, processing and vertical test performance cavities. also...
We describe the low power and high performance of planar waveguide windows designed fabricated by Thomson Tubes tested at LNS. These are intended for use in phase III upgrade CESR.
The new superconducting RF system consisting of four single-cell cavity modules is an important part the CESR Luminosity Upgrade. We describe commissioning first three accelerating modules. This includes in situ testing and conditioning, pulsed power beam processing windows, various cryogenic feedback loops, measuring spacing phasing with beam, high-current operation.
The beam tubes on the CESR-B cavity have been designed so that all of higher order modes (HOM's) will propagate out cavity. To damp these to Q values /spl sim/100, we proposed use HOM loads are an integral part tube, though located outside cryostat. absorbing medium is ferrite tiles which bonded inside a 304 series stainless steel water-cooled jacket. bonding agent alloy melts at sim/220/spl deg/C. This provides good thermal, as well electrical, conductivity. Calculations indicate provide...
The CESR luminosity upgrade plan calls for shortening bunch length to 1 cm. Such can be achieved by installing two more superconducting cavities increase total RF voltage. system necessary accommodate this change is discussed.
The prototype superconducting cavity system for CESR-Phase III was tested in CESR August 1994. performance of the very gratifying. operated gradients 4.5-6 MV/m and accelerated beam currents up to 220 mA. This current is a factor 3 above world record 67 mA SRF[1]. high circulating did not increase heat load or present any danger cavity. No instability attributable SRF encountered. A maximum 155 kW rf power transferred 120 beam. window subjected 125 reflected processed easily. In travelling...