Estimation of Hydrodynamical Model Parameters from the Invariant Spectrum and the Bose-Einstein Correlations of pi-mesons Produced in (pi+/K+)p Interactions at 250 GeV/c

The invariant spectra of pi- mesons produced in (pi+/K+)p interactions at 250 GeV/c are analysed in the framework of the hydrodynamical model of three-dimensionally expanding cylindrically symmetric finite systems. A satisfactory description of experimental data is achieved. The data favour the pattern according to which the hadron matter undergoes predominantly longitudinal expansion and non-relativistic transverse expansion with mean transverse velocity = 0.20(7), and is characterized by a large temperature inhomogeneity in the transverse direction: the extracted freeze-out temperature at the center of the tube and at the transverse rms radius are 140(3) MeV and 82(7) MeV, respectively. The width of the (longitudinal) space-time rapidity distribution of the pion source is found to be Delta eta = 1.36(2). Combining this estimate with results of the Bose-Einstein correlation analysis in the same experiment, one extracts a mean freeze-out time of the source of = 1.4(1) fm/c and its transverse geometrical rms radius, R_G (rms)=1.2(2) fm.Comment: latex, 14 pages, 5 figure

Boost Invariance and Multiplicity Dependence of the Charge Balance Functionin π+p\pi^{+}p and K+pK^{+}p Collisions at s=22\sqrt s= 22 GeV/c

Boost invariance and multiplicity dependence of the charge balance function are studied in \pi^{+}\rp and \rK^{+}\rp collisions at 250 GeV/$c$ incident beam momentum. Charge balance, as well as charge fluctuations, are found to be boost invariant over the whole rapidity region, but both depend on the size of the rapidity window. It is also found that the balance function becomes narrower with increasing multiplicity, consistent with the narrowing of the balance function when centrality and/or system size increase, as observed in current relativistic heavy ion experiments.Comment: 4 pages, 5 figures, Revte

Entropy Analysis in \pi^{+}\rp and \rK^{+}\rp Collisions at s=22\sqrt{s}=22 GeV

The entropy properties are analyzed by Ma's coincidence method in \pi^{+}\rp and \rK^{+}\rp collisions of the NA22 experiment at 250 GeV/$c$ incident momentum. By using the R\'{e}nyi entropies, we test the scaling law and additivity properties in rapidity space. The behavior of the R\'{e}nyi entropies as a function of the average number of particles is investigated. The results are compared with those from the {\sc Pythia} Monte Carlo event generator.Comment: LaTeX, 11 pages, 5 figure to be appeared in Acta Phys. Pol.

Estimation of hydrodynamical model parameters from the invariant spectrum and the Bose-Einstein correlations of π\pi-mesons produced in (π+/K+)p\pi^{+}/K^{+})p interactions at 250 GeV/c

The invariant spectra of pi- mesons produced in (pi+/K+)p interactions at 250 GeV/c are analysed in the framework of the hydrodynamical model of three-dimensionally expanding cylindrically symmetric finite systems. A satisfactory description of experimental data is achieved. The data favour the pattern according to which the hadron matter undergoes predominantly longitudinal expansion and non-relativistic transverse expansion with mean transverse velocity = 0.20(7), and is characterized by a large temperature inhomogeneity in the transverse direction: the extracted freeze-out temperature at the center of the tube and at the transverse rms radius are 140(3) MeV and 82(7) MeV, respectively. The width of the (longitudinal) space-time rapidity distribution of the pion source is found to be Delta eta = 1.36(2). Combining this estimate with results of the Bose-Einstein correlation analysis in the same experiment, one extracts a mean freeze-out time of the source of = 1.4(1) fm/c and its transverse geometrical rms radius, R_G (rms)=1.2(2) fm.The invariant spectra of pi- mesons produced in (pi+/K+)p interactions at 250 GeV/c are analysed in the framework of the hydrodynamical model of three-dimensionally expanding cylindrically symmetric finite systems. A satisfactory description of experimental data is achieved. The data favour the pattern according to which the hadron matter undergoes predominantly longitudinal expansion and non-relativistic transverse expansion with mean transverse velocity = 0.20(7), and is characterized by a large temperature inhomogeneity in the transverse direction: the extracted freeze-out temperature at the center of the tube and at the transverse rms radius are 140(3) MeV and 82(7) MeV, respectively. The width of the (longitudinal) space-time rapidity distribution of the pion source is found to be Delta eta = 1.36(2). Combining this estimate with results of the Bose-Einstein correlation analysis in the same experiment, one extracts a mean freeze-out time of the source of = 1.4(1) fm/c and its transverse geometrical rms radius, R_G (rms)=1.2(2) fm

Self-affine scaling from non-integer phase-space partition in π+p\pi^{+}p and K+pK^{+}p collisions at 250 GeV/cc

A factorial-moment analysis with real (integer and non-integer) phase space partition is applied to $\pi^+$p and K$^+$p collisions at 250 GeV/$c$. Clear evidence is shown for self-affine rather than self-similar power-law scaling in multiparticle production. The three-dimensional self-affine second-order scaling exponent is determined to be 0.061$\pm$0.010.A factorial-moment analysis with real (integer and non-integer) phase space partition is applied to $\pi^+$p and K$^+$p collisions at 250 GeV/$c$. Clear evidence is shown for self-affine rather than self-similar power-law scaling in multiparticle production. The three-dimensional self-affine second-order scaling exponent is determined to be 0.061$\pm$0.010.A factorial-moment analysis with real (integer and non-integer) phase space partition is applied to $\pi^+$p and K$^+$p collisions at 250 GeV/$c$. Clear evidence is shown for self-affine rather than self-similar power-law scaling in multiparticle production. The three-dimensional self-affine second-order scaling exponent is determined to be 0.061$\pm$0.010.A factorial-moment analysis with real (integer and non-integer) phase space partition is applied to π + p and K + p collisions at 250 GeV/ c . Clear evidence is shown for self-affine rather than self-similar power-law scaling in multiparticle production. The three-dimensional self-affine second-order scaling exponent is determined to be 0.061±0.010

Large Self-affine fractality in \p^+p and K+^+p collisions at 250 GeV/cc

Taking into account the anisotropy of phase space in multiparticle production, a self-affine analysis of factorial moments was carried out on the NA22 data for \p^+\Pp and \PK^+\Pp collisions at 250 GeV/$c$. Within the transverse plane, the Hurst exponents measuring the anisotropy are consistent with unit value (i.e. no anisotropy). They are, however, only half that value when the longitudinal direction is compared to the transverse ones. Fractality, indeed, turns out to be self-affine rather than self-similar in multiparticle production. In three-dimensional phase space, power-law scaling is observed to be better realized in self-affine than in self-similar analysis.Comment: 10 pages and 4 figure

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters