119185315
Effects of the detection efficiency on multiplicity distributions
In this paper we investigate how a finite detection efficiency affects three popular multiplicity distributions, namely the Poisson, the Binomial and the Negative Binomial distributions. We found that a multiplicity-independent detection efficiency does not change the characteristic of a distribution, while a multiplicity-dependent detection efficiency does. We layout a procedure to study the deviation of moments and their derivative quantities from the baseline distribution due to a multiplicity-dependent detection efficiency.
17737818
Non-photonic electron–hadron correlations at STAR
We present STAR's measurements of azimuthal correlations between non-photonic electrons and charged hadrons in p+p, Cu+Cu and Au+Au collisions at GeV. In p+p collisions, from the non-photonic e?h correlation we have extracted the relative B meson semi-leptonic decay contributions to non-photonic electrons up to electron pt ~ 9 GeV/c. In central Cu+Cu and Au+Au collisions where a dense medium is created, we find that the e?h correlation on the away side of the trigger non-photonic electron has been modified in comparison with the expectation from PYTHIA simulations.
14494427
Highlights from STAR: probing the early medium in heavy ion collisions
Abstract We present highlights of recent results from the STAR Collaboration at RHIC, focusing on the properties of the early medium created in heavy ion collisions. We emphasize the strangeness production including the observation of a hypernucleus (the hypertriton), the observation of reaction-plane-dependent angular correlation of charged particles searching for local strong parity violation effects in heavy ion collisions, and the evaluation of the medium viscosity from measurements of elliptic flow. We discuss STAR's plan for the “Critical Point Search” program at RHIC.
122537214
Search for local parity violation with STAR ZDC-SMD
Parity-odd domains are predicted to lead to charge separation of quarks along the orbital momentum of the system created in non-central relativistic heavy ion collisions. A signal consistent with several of the theoretical expectations has been detected by STAR, with a three particle azimuthal correlator which is a -even observable, but still sensitive to the charge separation effect. In this correlator, the first two particles are used to reveal the physics of interest, and the third particle serves as a reference for the reaction plane. In this work, to minimize the non-parity correlation between the third particle and the first two, we utilize the spectator neutrons detected by STAR ZDC-SMDs to define the event plane. The 1st-order event plane thus obtained can also be used to study the global strong parity violation effect, and to provide further systematic checks for this analysis. We report measurements of both -even and -odd observables using the STAR ZDC-SMDs in Au+Au at 200 GeV. The results are presented as a function of collision centrality, particle separation in rapidity and transverse momentum (pT). Systematic checks on the impact from the directed flow will also be discussed.
11542069
Observation of a critical gradient threshold for electron temperature fluctuations in the DIII-D Tokamak.
A critical gradient threshold has been observed for the first time in a systematic, controlled experiment for a locally measured turbulent quantity in the core of a confined high-temperature plasma. In an experiment in the DIII-D tokamak where L(T(e))(-1) = |∇T(e)|/T(e) and toroidal rotation were varied, long wavelength (k(θ)ρ(s) ≲ 0.4) electron temperature fluctuations exhibit a threshold in L(T(e))(-1): below, they change little; above, they steadily increase. The increase in δT(e)/T(e) is concurrent with increased electron heat flux and transport stiffness. Observations were insensitive to rotation. Accumulated evidence strongly enforces the identification of the experimentally observed threshold with ∇T(e)-driven trapped electron mode turbulence.
119253082
Non-photonic electron-hadron correlations and non-photonic electron v2 at STAR/RHIC
Abstract Non-photonic electrons ( p T > 3 GeV / c ) represent the directions of the parent heavy quarks, and their angular correlations with charged hadrons provide a good tool to study the relative contributions from D and B meson decays in p+p collisions, as well as the flavor-dependence of the energy loss mechanism in A+A collisions. We review the disentanglement of charm and bottom contributions to non-photonic electrons in p+p collisions at s = 200 GeV at RHIC. B decay contribution is approximately 50% at the electron transverse momentum of p T > 5 GeV / c from STAR results. Incorporating the energy loss ( R AA ) information of non-photonic electrons, the result indicates a B meson suppression at high p T in heavy ion collisions. We also present non-photonic electron-hadron correlations in d+Au collisions as a baseline reference for the investigation of the heavy quark energy loss in A+A collisions. The interactions between heavy quarks and the QCD medium can lead to a non-zero “elliptic flow” parameter ( v 2 ) of D and B mesons which can be studied through v 2 of non-photonic electrons. Preliminary v 2 measurements for non-photonic electrons are shown to be lower than v 2 of charged hadrons (or K S 0 , Λ ) for 200 GeV Au+Au collisions.
112824375
Energy Recovery Transport Design for Peking University FEL
A free-electron laser based on a superconducting linac is under construction in Peking University. To increase FEL output power, energy recovery is chosen as one of the most potential and popular ways. The design of a beam transport system for energy recovery is presented, which is suitable for the Peking University construction area. Especially, a chicane structure is chosen to change path length at ±20 degree and M56 in the arc is adjusted for fully bunch compression.
110815008
Implementation of a DC Bump at the Storage Ring Injection Straight Section
The NSLS II beam injection works with a DC septum, a pulsed septum and four fast kicker magnets. The kicker power supplies each produce a two revolution period pulsed field, 5.2 {micro}s half sine waveform, using {approx}5kA drive voltage. The corresponding close orbit bump amplitude is {approx}15mm. It is desired that the bump is transparent to the users for top-off injection. However, high voltage and short pulse power supplies have challenges to maintain pulse-to-pulse stability and magnet-to-magnet reproducibility. To minimize these issues, we propose implementing a DC local bump on top of the fast bump to reduce the fast kicker strength by a factor of 2/3. This bump uses two storage ring corrector magnets plus one additional magnet at the septum to create a local bump. Additionally, these magnets could provide a DC bump to simulate the septum position effects on the store beam lifetime. This paper presents the detail design of this DC injection bump and related beam dynamics.
122329723
MODIFIED HAWKING RADIATION FROM A KERR–NEWMAN BLACK HOLE DUE TO BACK-REACTION
Hawking radiation from a general Kerr–Newman black hole is investigated using Damour–Ruffini's method. Considering the back-reaction of particle's energy, charge and angular momentum to the spacetime, we obtain a modified nonthermal spectrum. Maybe the information loss paradox can be explained, furthermore, the result is also consistent with the result obtained using Parikh and Wilczek's method.
118032595
Progress on Analytical Modeling of Coherent Electron Cooling
We report recent progresses on analytical studies of Coherent Electron Cooling. The phase space electron beam distribution obtained from the 1D FEL amplifier is applied to an infinite electron plasma model and the electron density evolution inside the kicker is derived. We also investigate the velocity modulation in the modulator and obtain a closed form solution for the current density evolution for infinite homogeneous electron plasma.
119251875
Annihilation rate of 2++ charmonium and bottomonium
Abstract Two-photon annihilation rates of 2 + tensor charmonium and bottomonium up to third radial excited states are estimated in the relativistic Salpeter method. Full Salpeter equation for 2 + tensor state is solved with a well defined relativistic wave function and we calculated the annihilation amplitude using the Mandelstam formalism. Our estimates of the decay widths are: Γ ( χ c 2 → 2 γ ) = 501 eV , Γ ( χ c 2 ′ → 2 γ ) = 534 eV , Γ ( χ b 2 → 2 γ ) = 7.4 eV and Γ ( χ b 2 ′ → 2 γ ) = 7.7 eV . We also give total decay widths of the lowest states estimated by the two-gluon decay rates, and the results are: Γ tot ( χ c 2 ) = 2.64 MeV , Γ tot ( χ b 2 ) = 0.220 MeV and Γ tot ( χ b 2 ′ ) = 0.248 MeV .