Study of W± boson in the ALICE muon spectrometer: considerations and analysis using the HLT tool

W± bosons produced in proton-proton collisions can be observed in the ALICE muon spectrometer via their decay into single muons at a transverse momentum, pt ~ Mw/2 40 GeV/c. However the identification of these single muons is complicated by a large amount of muonic background, especially in the low pt region. Therefore, it is necessary to apply precise pt cuts below the region of interest. This can be done by means of the High Level Trigger (HLT). In this paper we present the performance of detecting high pt muons at the HLT level. In order to improve the momentum resolution of the L0 trigger, fast clusterization of the tracking chambers together with L0 trigger matching and fast tracking reconstruction is applied. This will reduce the background in the high pt muon analysis

Studies of the Giant Dipole Resonance in 27^{27}Al, 40^{40}Ca, 56^{56}Fe, 58^{58}Ni and 208^{208}Pb with high energy-resolution inelastic proton scattering under 0∘^\circ

A survey of the fine structure of the Isovector Giant Dipole Resonance (IVGDR) was performed, using the recently commissioned zero-degree facility of the K600 magnetic spectrometer at iThemba LABS. Inelastic proton scattering at an incident energy of 200 MeV was measured on $^{27}$Al, $^{40}$Ca, $^{56}$Fe, $^{58}$Ni and $^{208}$Pb. A high energy resolution ($\rm{\Delta}\it{E} \simeq$ 40 keV FWHM) could be achieved after utilising faint-beam and dispersion-matching techniques. Considerable fine structure is observed in the energy region of the IVGDR and characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The comparison with Quasiparticle-Phonon Model (QPM) calculations provides insight into the relevance of different giant resonance decay mechanisms. Photoabsorption cross sections derived from the data assuming dominance of relativistic Coulomb excitation are in fair agreement with previous work using real photons.Comment: 15 pages, 15 figure

Proton inelastic scattering to continuum studied with antisymmetrized molecular dynamics

Intermediate energy (p,p$'$x) reaction is studied with antisymmetrized molecular dynamics (AMD) in the cases of $^{58}$Ni target with $E_p = 120$ MeV and $^{12}$C target with $E_p =$ 200 and 90 MeV. Angular distributions for various $E_{p'}$ energies are shown to be reproduced well without any adjustable parameter, which shows the reliability and usefulness of AMD in describing light-ion reactions. Detailed analyses of the calculations are made in the case of $^{58}$Ni target and following results are obtained: Two-step contributions are found to be dominant in some large angle region and to be indispensable for the reproduction of data. Furthermore the reproduction of data in the large angle region \theta \agt 120^\circ for $E_{p'}$ = 100 MeV is shown to be due to three-step contributions. Angular distributions for E_{p'} \agt 40 MeV are found to be insensitive to the choice of different in-medium nucleon-nucleon cross sections $\sigma_{NN}$ and the reason of this insensitivity is discussed in detail. On the other hand, the total reaction cross section and the cross section of evaporated protons are found to be sensitive to $\sigma_{NN}$. In the course of the analyses of the calculations, comparison is made with the distorted wave approach.Comment: 16 pages, 7 Postscript figure

Wavelet signatures of KK-splitting of the Isoscalar Giant Quadrupole Resonance in deformed nuclei from high-resolution (p,p′') scattering off 146,148,150^{146,148,150}Nd

The phenomenon of fine structure of the Isoscalar Giant Quadrupole Resonance (ISGQR) has been studied with high energy-resolution proton inelastic scattering at iThemba LABS in the chain of stable even-mass Nd isotopes covering the transition from spherical to deformed ground states. A wavelet analysis of the background-subtracted spectra in the deformed 146,148,150Nd isotopes reveals characteristic scales in correspondence with scales obtained from a Skyrme RPA calculation using the SVmas10 parameterization. A semblance analysis shows that these scales arise from the energy shift between the main fragments of the K = 0, 1 and K = 2 components.Comment: 7 pages, 6 figure

Binary projectile fragmentation of 12C at an incident energy of 33.3 MeV/nucleon

Direct binary projectile fragmentation is being investigated for the case where a 400 MeV 12C projectile breaks up into an particle and a 8Be fragment in the interaction with a thin 93Nb and 197Au target. While the 8Be fragments were measured at 9 , the correlated particles were detected in an angular range between 16 and 30 on the opposite side of the beam. From the preliminary results presented here one may obtain information on the amount of quasi-elastic fragmentation (both fragments do not suffer any further interactions after they are produced). These experimental results indicate that the quasi-elastic break-up process is the dominant contribution to the measured correlation spectra. As was also observed in earlier work, the most forward quasi-elastically emitted particles have energies exceeding the beam velocity

Measurement of p + d -> 3He + eta in S(11) Resonance

We have measured the reaction p + d -> 3He + eta at a proton beam energy of 980 MeV, which is 88.5 MeV above threshold using the new ``germanium wall'' detector system. A missing--mass resolution of the detector system of 2.6% was achieved. The angular distribution of the meson is forward peaked. We found a total cross section of (573 +- 83(stat.) +- 69(syst.))nb. The excitation function for the present reaction is described by a Breit Wigner form with parameters from photoproduction.Comment: 8 pages, 2 figures, corrected typos in heade

Nuclear Transparency to Intermediate-Energy Protons

Nuclear transparency in the (e,e'p) reaction for 135 < Tp < 800 MeV is investigated using the distorted wave approximation. Calculations using density-dependent effective interactions are compared with phenomenological optical potentials. Nuclear transparency is well correlated with proton absorption and neutron total cross sections. For Tp < 300 MeV there is considerable sensitivity to the choice of optical model, with the empirical effective interaction providing the best agreement with transparency data. For Tp > 300 MeV there is much less difference between optical models, but the calculations substantially underpredict transparency data and the discrepancy increases with A. The differences between Glauber and optical model calculations are related to their respective definitions of the semi-inclusive cross section. By using a more inclusive summation over final states the Glauber model emphasizes nucleon-nucleon inelasticity, whereas with a more restrictive summation the optical model emphasizes nucleon-nucleus inelasticity; experimental definitions of the semi-inclusive cross section lie between these extremes.Comment: uuencoded gz-compressed tar file containing revtex and bbl files and 5 postscript figures, totalling 31 pages. Uses psfi

Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR

Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (mu_B > 500 MeV), effects of chiral symmetry, and the equation-of-state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2022, in the context of the worldwide efforts to explore high-density QCD matter.Comment: 15 pages, 11 figures. Published in European Physical Journal

High-Energy-Resolution Inelastic Electron and Proton Scattering and the Multiphonon Nature of Mixed-Symmetry 2 States in 94 Mo

High-energy-resolution inelastic electron scattering (at the S-DALINAC) and proton scattering (at iThemba LABS) experiments permit a thorough test of the nature of proposed one-and two-phonon symmetric and mixed-symmetric 2 states of the nucleus 94 Mo. The combined analysis reveals the onephonon content of the mixed-symmetry state and its isovector character suggested by microscopic nuclear model calculations. The purity of two-phonon 2 states is extracted. DOI: 10.1103/PhysRevLett.99.092503 PACS numbers: 21.10.Re, 25.30.Dh, 25.40.Ep, 27.60.+j Collective valence-shell excitations are a generic feature of strongly-coupled mesoscopic quantum systems. A prime example of a two-component system is the atomic nucleus formed by protons and neutrons. The microscopic structure of collective nuclear excitations with respect to their proton-neutron content is a central issue of nuclear structure physics with general implications for the physics of composite strongly-coupled quantum systems. Low-energy nuclear valence-shell excitations usually possess the lowest possible isospin quantum number T &lt; jN ÿ Zj=2. Nevertheless, the symmetry character of their proton-neutron coupling can vary. This fact is evident in the framework Recently, one-and two-phonon MSSs were investigated in vibrational nuclei with proton and neutron numbers near closed shells, e.g., in the nuclide 94 Mo [5]. Comprehensive spectroscopic information on low-spin states has been achieved up to an excitation energy of about 4 MeV It is the purpose of this Letter to report a combined study of electron and proton scattering differential cross sections for J 2 one-and two-phonon FSSs and MSSs in 94 Mo. The selectivity of both reactions to one-phonon components in the excited state wave functions allows to extract for the first time the small one-phonon contributions to the two-phonon candidates. The proton-neutron symmetry character can be derived since electron scattering couples to the proton distributions, while proton scattering is dominated by the isoscalar central part of the effective proton-nucleus interaction. We thereby introduce a new approach establishing a multiphonon character of nuclear MSSs based on scattering data complementary to -ray spectroscopy. The (e; e 0 ) experiments were carried out at the highenergy-resolution magnetic spectromete