122307207
Isospin effect of fragmentation reactions induced by intermediate energy heavy ions and its disappearance
The fragments produced in the reaction of O-18 + Be-9 at 60 MevV/nucleon were measured experimentally. The isotopic distribution of the fragmentation reaction products was well reproduced by using a modified statistical abrasion-ablation model This model predicts that the fragment isotopic distribution at a fixed atomic number Z shifts towards the neutron rich side for the neutron-rich projectile. This isospin effect will decrease with decreasing the fragment atomic number Z and disappear when (Z(proj)-Z)/Z(proj) becomes larger than 0.5. It was shown that the disappearance of the isospin effect of fragmentation reaction is induced by the geometry effect in abrasion stage and the evaporation effect later.
125737170
Search for the top quark decaying to a charged Higgs boson in anti-p p collisions at S**2 (1/2) = 1.8-TeV
53131397
Energy and system-size dependence of two- and four-particle $v_2$ measurements in heavy-ion collisions at RHIC and their implications on flow fluctuations and nonflow
We present STAR measurements of azimuthal anisotropy by means of the two- and four-particle cumulants $v_2$ ($v_2\{2\}$ and $v_2\{4\}$) for Au+Au and Cu+Cu collisions at center of mass energies $\sqrt{s_{_{\mathrm{NN}}}} = 62.4$ and 200 GeV. The difference between $v_2\{2\}^2$ and $v_2\{4\}^2$ is related to $v_{2}$ fluctuations ($\sigma_{v_2}$) and nonflow $(\delta_{2})$. We present an upper limit to $\sigma_{v_2}/v_{2}$. Following the assumption that eccentricity fluctuations $\sigma_{\epsilon}$ dominate $v_2$ fluctuations $\frac{\sigma_{v_2}}{v_2} \approx \frac{\sigma_{\epsilon}}{\epsilon}$ we deduce the nonflow implied for several models of eccentricity fluctuations that would be required for consistency with $v_2\{2\}$ and $v_2\{4\}$. We also present results on the ratio of $v_2$ to eccentricity.
123856190
Existence of a proton halo in Al-23 and its significance
Reaction cross section sigma(R) of proton-rich isotones (N = 10) near Al-23 and Al isotopes (Al23-28) on C target have been measured at intermediate energies around 30 MeV/nucleon. An abnormal increase of the experimental sigma(R) is observed for Al-23 and it suggests that there is an anomalously large matter rms radius in Al-23. Together with the very weakly binding of the last proton (S-p = 0.125 MeV), it indicates that there is a proton halo in Al-23. This conclusion is also supported by the difference factor d which is deduced from the measured and theoretical sigma(R) in the Glauber or Boltzmann-Uehling-Uhlenbeck model and is used for the manifest of halo phenomena. The theoretical calculation based,on the relativistic density dependent Hartree model shows that there is a proton halo when the last proton is in the 2s(1/2) orbit in Al-23. The significance of the proton halo in Al-23 is discussed.
119972193
Measurements of total reaction cross sections for some light nuclei at intermediate energies
Measurements of the total reaction cross section for C12-16, N14-17, and O16-18 on carbon target at intermediate energies were performed on the Radioactive Ion Beam Line of the Heavy ion Research Facility in Lanzhou. A larger enhancement of sigma(R) for C-15 was observed than for its neighbors. Evidence for possible anomalous nuclear structure in C-15 was revealed in the analysis of the total reaction cross section in terms of the difference factor d.
45929403
Sequential Decay Distortion of Goldhaber Model Widths for Spectator Fragments
The primary fragment momentum distributions from AMD-V can be described by a Gaussian shape characterized by a width σ. Figure 1: The three momentum widths, σ , σ , σ , as a removed from a nucleus that originally has A0 nucleons, a nucleus consisting of K nucleons will emerge. For this fragment of K nucleons, Goldhaber [1] showed that the momentum width, σ, could be expressed as: σ = σ0 sqrt [K(A0 K)/(A0 – 1)], where σ0, the reduced momentum width, is related to the intrinsic Fermi motion of a single nucleon, i.e.,: σ0 = sqrt (1/5)PF. Based upon electron scattering ments of Fermi momenta, σ is expected to be ≈ 112-116 MeV/c. However, σ ≈ MeV/c [2]. Some theoretical works [3] have attempted to explain this difference. However, the answers were still absent. In this work, we studied peripheral collisions of 200 MeV/nucleon Ar + Al with AMD-V model [4] and followed with the afterbuner (GEMINI) [5]. In the AMD-V model, initial width of the nucleon momentum distribution is ~ 105 MeV/c for Ar and ~ 101 MeV/c for Al. These values are less than expected from electron scattering measurements, but are still in a reasonable range. The fragment mass numbers and the three momentum widths, σPx, σPy, σPz, are plotted
118434873
Testing the QCD fragmentation mechanism on heavy quarkonium production at LHC
We calculate the fragmentation function for charm quark into J/psi at the QCD next-to-leading-order (NLO) and find that the produced J/psi is of larger momentum fraction than it is at the leading-order. Based on the fragmentation function and partonic processes calculated at the NLO, the transverse momentum distribution on J/psi hadroproduction associated with a charm c (or \bar{c}) jet are predicted. We find that the distribution is enhanced by a factor of 2.0--3.3 at the NLO as p_t increased from 10 GeV to 100 GeV and it is measurable at the LHC with charm tagger. The measurement at the LHC will supply a first chance to directly test the QCD fragmentation mechanism on heavy quarkonium production where the fragmentation function is calculable in perturbative QCD. It is also applied to J/psi (Upsilon) production in the decay of Z^0 (top quark).
18308235
Search for new particles in hadronic events with isolated photons
Abstract A search for the neutral Higgs boson in the processes e + e − → Z → H 0 γ → q q γ and e + e − → Z → Z ∗ H 0 → q q γγ has been performed using 2.8 million hadronic Z decays collected with the L3 detector at LEP from 1991 through 1994. No evidence for these processes has been observed. Upper limits at 95% confidence level for the corresponding cross sections have been set and the results have been compared with theoretical predictions beyond the Standard Model.
109333657
RF Design of X-Band RF Deflector for Femtosecond Diagnostics of LCLS Electron Beam
We designed a successful constant impedance traveling wave X-band rf deflector for electron beam diagnostics at the 14 GeV SLAC Linac Coherent Light Source (LCLS). This is the first practical deflector built with a waveguide coupler. The 1-meter rf deflector produces 24 MeV peak transverse kick when powered with 20 MW of 11.424 GHz rf. The design is based on our experience with high gradient X-band accelerating structures. Several deflectors of this design have been built at SLAC and are currently in use. Here we describe the design and distinguishing features of this device.
120627775
Systematic behavior in the isospin dependence of projectile fragmentation of mirror nuclei with A = 20?60
The cross sections of the fragments that are produced by the 80 A MeV |Tz| = 2 mirror nuclei 20Mg/20O, 24Si/24Ni, 36Ca/36S, 40Ti/40Ar, 44Ca/44Cr and 60Ni/60Ge colliding on the 12C target are calculated using the statistical abrasion?ablation model. The isospin dependence of the projectile fragmentation (or the isospin effect) in the fragment cross section distributions of the A = 20?60 mirror projectile nuclei is studied systematically. The isospin effect in the fragment cross section distributions is found to decrease and even disappear with increasing violence of the collisions. The isospin effect is found strongly related to the different proton and neutron density distributions. It is suggested that the isospin effect in the fragment cross section distributions may serve as an observation to extract the density distributions of asymmetric nucleus.
13062064
Polar outflows in six broad absorption line quasars
Using radio observations by FIRST and NVSS, we build a sample of 151 radio-variable quasars selected from the Sloan Digital Sky Survey Data Release 3 (SDSS DR3). Six (and probably another two) of these objects are classified as broad absorption line (BAL) quasars and show radio flux variations of a few tens of percent within 1.5-5 yr. Such large amplitudes of variations imply brightness temperatures much higher than the inverse Compton limits (10(12) K) in all these BAL quasars, suggesting the presence of relativistic jets beaming toward the observer. The angles between the outflow and the jet are constrained to be less than similar to 20 degrees. Such BAL quasars with polar outflows are beyond the simple unification models of BAL and non-BAL quasars, which hypothesize BAL quasars as otherwise normal quasars seen nearly edge-on.