Analysis of transverse momentum distributions forpp interactions at 360 GeV/c in the framework of a quark-diquark fragmentation model

Using a quark-diquark fragmentation model, in which either the Field-Feynman or the Lund model is coupled with a quark-diquark distribution function, we study transverse momentum distributions,p _T, for the inclusive reactionspp→hadron +anything at 360 GeV/c. We find that a primordial mean transverse momentum 〈k _T〉?0.4 GeV/c can well reproduce thep _T ² distributions of charged hadrons, π⁰,K _s ⁰ , Λ⁰,K ^* and Σ^* and the Feynmanx?p _T correlations. We confirm that a diquark in a proton plays an important rôle in reproducing thex?p _T correlation of Λ⁰.     

High resolution spectroscopy of stable xenon isotopes

In this paper we investigate the hyperfine structure and isotope shift of four near infrared xenon transitions by means of a semiconductor diode laser. Doppler free spectra were obtained by using either a saturation spectroscopy technique in cell or a laser induced fluorescence technique on a collimated atomic metastable beam. The hyperfine coupling constants of ¹²⁹Xe and ¹³¹Xe were determined for the levels 1s₅, 1s₄, 1s₄2, 2p₂, 2p₄ and 2p₆ (Paschen notation). Moreover, a systematic study of the isotope shift was performed for the 1s₃ → 2p₄ and 1s₅ → 2p₆ transitions for which all the stable isotopes ^128–131Xe , ¹³²Xe, ¹³⁴Xe, and ¹³⁶Xe were fully resolved. This revised version was published online in August 2006 with corrections to the Cover Date.     

Neutral transverse momentum spectra in 60 and 200A·GeV16O+nucleus and proton+nucleus reactions

Transverse momentum (p _T) distributions fo inclusive photons and neutral pions at midrapidity are measured with a lead glass calorimeter in 60 and are measured with a lead glass calorimeter in 60 and 200A·Gev¹⁶O+nucleus and and proton+nucleus reactions. Inclusive photon distributions are compared for central and peripheral reactions. The degree of centrality is determined either from the charged particle multiplicity or from the remaining projectile energy in the forward direction. Deviations from a nucleus+nucleus interaction model based upon linear extrapolation from p+p reactions are observed in central¹⁶O+Au data. The variation of theaverage transverse momentum is investigated as function of centrality. The target-mass and energy dependence of π⁰ p _T distributions are presented. For¹⁶O+Au a change of slope in these distributions is observed atp _t ≈0.8 GeV/c compatible with hydrodynamic expansion models.     

Isospin dependence of projectile fragmentation and neutron-skin thickness of neutron-rich nuclei

By investigating the cross section distributions of fragments produced in the 140 A MeV ^40,48Ca+⁹Be and 1 A GeV ^124,136Xe+Pb reactions, the isospin dependence of projectile fragmentation in fragment production is studied. In the framework of the statistical abrasion-ablation model, the 1 A GeV ¹³⁶Xe+²⁰⁸Pb reaction is calculated. By adjusting the diffuseness parameter in neutron density distribution of ¹³⁶Xe, we find the isospin dependence of projectile fragmentation in fragment production is sensitive to the neutron-skin thickness of the projectile nucleus.     

A search for deeply bound pionic states of xenon produced in the 136Xe(d, 3He)135Xeπ-bound reaction

A search for deeply bound pionic states of xenon produced in the ¹³⁶Xe(d, ³He)¹³⁵Xe_π-bound reaction at E _d = 500 MeV is reported. The population of the 1s pionic-atom state of ¹³⁵Xe is observed on the predicted level of the cross section ～ 40 μb/sr. The binding energy of the 1s state, B = 2.9 ± 0.5 MeV, however, is lower than theoretically predicted.     

Di-jet correlation in Au+Au and Cu+Cu Collisions from PHENIX

PHENIX has measured the two-particle azimuth correlation in Au+Au at √s=200 GeV. Jet shape and yield at the away side are found to be strongly modified at intermediate and low p _T, and the modifications vary dramatically with p _T and centrality. At high p _T, away side jet peak reappears but the yield is suppressed. Similar jet strength is found for Au+Au and Cu+Cu collisions with similar number of participant nucleons.     

Kinetic freeze-out s pectra of identified particles produced in p–Pb collisions at $$\sqrt {s_{NN} }$$ = 5.02 TeV

We study the transverse momentum spectra of identified pions (π^– + π⁺), kaons ((K ^– + K ⁺), K ₀ ^s ), protons (p + p?) and lambda hyperons (Λ + Λ?) produced at mid-rapidity (0 < y _cm < 0.5) in most central (0?5)% p–Pb collisions at \(\sqrt {s_{NN} }\) = 5.02 TeV in comparison with a Unified Statistical Thermal Freeze-out Model (USTFM). The measurements for pions are reported upto p _T = 3 GeV, the kaons (K ^– + K ⁺) are reported upto p _T = 2.5 GeV, K ₀ ^s is reported upto p _T = 7 GeV, and the baryons (protons and lambda hyperons) are reported upto p _T = 3.5 GeV. A good agreement is seen between the calculated results and the experimental data points taken from the ALICE experiment. The transverse momentum spectra are found to be flatter for heavy particles than for light particles. Bulk freeze-out properties in terms of kinetic freeze-out temperature and the transverse collective flow velocity are extracted from the fits of the transverse momentum spectra of these hadrons. The effect of resonance decay contributions has also been taken care of.     

Inclusive ϱ0 production in γp interactions at 2.8, 4.7, and 9.3 GeV

Inclusive ?⁰ production in γp → ?⁰ + anything is studied at 2.8, 4.7, and 9.3 GeV, using the SLAC linearly polarized backscattered laser photon beam and the 82 inch hydrogen bubble chamber. Over this energy range the inclusive inelastic ?⁰ cross section rises from 6.0 μb to 20.5 μb. The multiplicity, i.e. the average number of μ⁰ mesons per inelastic hadronic event, has an energy dependence consistent with 1n s.The inclusive cross section is studied as a function of Feynman x, c.m. rapidity, and p_T² variables, and is also broken down into exclusive channels. At 9.3 GeV a forward inelastic peak is observed in the x distribution, containing mainly polarized ?⁰ mesons. The cross section for this inealastic diffractive component is 2.7 ± 0.6 μb. The p_T² distributions are exponential with a slope of 3 ? 4 (GeV/c)^?2, similar to that found in inclusive ?⁰ production in pp and μp reactions.     

Observation of πo mesons with large transverse momentum in high-energy proton-proton collisions

Invariant cross-sections are presented for the inclusive reaction p + p → π^o + anything, Measurements of large transverse momentum π^o's (2.5 GeV/c<p_⊥<9 GeV/c) were made near 90° at the CERN ISR at five centre-of-mass energies (√s = 23.5, 30.6, 44.8, 52.7 and 62.4 GeV. At large p_⊥, the invariant cross-sections are seem to vary with s and p_⊥, in good agreement with a fit of the form Ap_⊥^?nF(p_⊥/√s), with n≈8 and F(p_⊥/√s)≈exp(?26p_⊥/√s).     

Large transverse momentum particle production in αα and pp collisions at the CERN ISR

The production of charged hadrons with high p_T in αα collisions at √s=126 GeV and pp collisions at √s=31 and 63 GeV is compared, and the structure of the events associated with the high-pT particles is studied. The probability of finding associated particles close to the trigger particle increases strongly between √s=31 and 63 GeV for pp collisions. For p_T>2.5GeV/c the αα/pp cross section ratio at the same energy per nucleon is measured to be 18.7 ± 2.0, to be compared with A² = 16, and a higher associated multiplicity is observed for αα.     

Mechanoluminescence of terbium and cerium sulfates in a noble-gas atmosphere

Lines of Ne (3p-3s, 550–800 nm) and Xe (6p-6s, 800–1050 nm; 7p-6s, 475 nm) have been detected in the mechanoluminescence spectrum of terbium and cerium sulfate crystallohydrates. The luminescence of noble gas is observed jointly with the known bands of Ce³⁺ and Tb³⁺ ions and N*₂ lines. The lines corresponding to excited Xe⁺ ions (500–550 nm), indicative of achievement of electric-field strengths on the order of 10⁷ V/cm during mechanoluminescence, are also observed. It is established that, during mechanoluminescence of Tb₂(SO₄)₃ · 8D₂O in an argon atmosphere under a pressure of 1.3 atm, mechanochemical reactions of decomposition of crystallization water (D₂O) molecules cause luminescence of OD radicals; this luminescence is initiated by electron impact occurring during electrization and in discharges in crystals during destruction.     

Production of Kr and Xe isotopes by interaction of197Au with 0.15–24 GeV protons

Cross sections and thick-target recoil properties of several Kr and Xe isotopes formed in the interaction of¹⁹⁷Au with 0.15–24 GeV protons have been determined in order to study their variations with mass product and incident energy. Noble gas isotopic composition and concentration have been obtained by using high sensitivity mass-spectrometry. The measurement of the experimental range, 2W(F+B), and of the forward-to-backward ratio,F/B, permits (with the help of a mathematical formalism based on the two-step model) the determination of some characteristics of nuclear reactions. The results are discussed in terms of fission and spallation mechanisms.     

Inclusive φ-meson production in 93 and 63 GeV hadron interactions

The inclusive reactions h+p→φ+X, (h=π^±,,K^±,p^±), are studied for 0?x_F?0.3 and p⊥ ? 1 GeV at 93 and and 63 GeV incident momentum. Differential cross sections dσ/dp_⊥² anddσ/dx_F are presented and are compared with predictions of the naive parton model.     

Double prompt photon production at high transverse momentum byπ − on protons at 280 GeV/c

A search for pairs of highp _T prompt photons produced in hydrogen by a 280 GeV/c incidentπ ^- beam has been carried out using a fine-grained electromagnetic calorimeter and the Omega spectrometer at the CERN SPS. Clear evidence for the existence of such events is found with a six standard deviation signal forp _T >3.0 GeV/c. The cross-sections are consistent with beyond leading order QCD calculations. A discussion on the determination of α _s is also presented.     

Energy and system size dependence of charged hadron transverse momentum spectra from Cu+Cu and Au+Au collisions at √S NN =62.4 and 200 GeV

The PHOBOS Collaboration has measured transverse momentum distributions of charged hadrons produced in Cu+Cu collisions at √s _NN =200 and 62.4 GeV. The nuclear modification factor R _AA ^N _part is calculated relative to p+p data at both collision energies as a function of collision centrality. For the same number of participating nucleons, R _AA ^N _part is essentially the same in both systems over the full range of p Tthat is measured. In addition, we observe that within experimental uncertainties, the ratio of 200 GeV to 62.4 GeV Cu+Cu yields has only a moderate centrality dependence and is consistent with the value previously measured in Au+Au collisions for a broad range of p _T.     

On gauge invariant nucleon spin decomposition

In the framework of a modified Fisher model, the ratio of the symmetry-energy coefficient to temperature (a _sym /T) is extracted from the fragment produced in the ^{124, 136}Xe induced reactions using the isobaric yield ratio methods based on different approximations. It is found that for nuclei with the same neutron excess (I ?? N ? Z) increases when the mass of the fragment increases, while for isobar a _sym /T decreases when I increases. It is also found that the extracted a _sym /T of the nucleus has very little dependence on the n/p ratio of the projectile, target, and the incident energies in the reaction.     

Particle composition at high transverse momenta in p-p-collisions in the central region at the CERN ISR

Preliminary measurements have been made at centre of mass energies √s = 31 and 44 GeV of the π, K and p production ratios at 90° for p_T between 2.0 and 3.5 GeV/c. The (K+p)/π ratio is given down to p_T = 1.4 GeV/c. No strong energy dependence is observed for these transverse momenta.     

The study of ungerade electronic states of the Xe2 molecules in the region of Xe*(5p 56p, 5d, 7s, 6d) by the resonance multiphoton ionization method

Electronic spectra of the Xe2 molecules in the energy range of 77700?C89300 cm^?1 are recorded. The method of resonance enhanced multiphoton ionization of molecules in a supersonic molecular beam was used, in which excitation of the molecules by three photons was followed by ionization caused by a fourth photon (the (3+1) REMPI method). Analysis of the vibrational structure of observed systems of bands yielded information about the dissociation energy and the molecular constants for ungerade states of molecules. On the basis of the Franck-Condon principle, the equilibrium distances for potential curves were estimated from the relative intensities in vibrational progressions. Data on 16 new electronic states of diatomic xenon molecules with the dissociation limits Xe ₂ ^* ?? XE(5p ^{6 1} S ₀) + Xe*(5p ⁵6p,5d, 7s, 7p) were obtained.     

Sub-Coulomb transfer and fission in collisions of129Xe,132Xe and136Xe with238U

Integral cross sections for fission and for one- and two-neutron transfer reactions in the system¹³²Xe+²³⁸U were measured radiochemically in the energy range 0.7≦E/E _Coul≦1. The excitation functions for fission and transfer are found to be essentially parallel below 0.85×E _Coul. Even at the lowest energies the transfer cross sections exceed the fission cross section by more than one order of magnitude. With the other projectiles¹²⁹Xe and¹³⁶Xe different transfer cross sections illustrating their sensitivity for the ground stateQ-values,Q _gg , are observed while the fission cross sections are the same as in the¹³²Xe +²³⁸U reaction. The fission data are interpreted in terms of a continuous transition between Coulomb fission and several transfer-induced fission processes.