I Das

Publications (90)200.76 Total impact

• Article: Transverse Momentum Distribution and Nuclear Modification Factor of Charged Particles in p+Pb Collisions at sqrt[s_{NN}]=5.02 TeV.

  B Abelev, J Adam, D Adamová, A M Adare, M M Aggarwal, G Aglieri Rinella, M Agnello, A G Agocs, A Agostinelli, Z Ahammed, [......], D Zhou, X Zhu, J Zhu, H Zhu, A Zichichi, A Zimmermann, G Zinovjev, Y Zoccarato, M Zynovyev, M Zyzak
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  ABSTRACT: The transverse momentum (p_{T}) distribution of primary charged particles is measured in minimum bias (non-single-diffractive) p+Pb collisions at sqrt[s_{NN}]=5.02 TeV with the ALICE detector at the LHC. The p_{T} spectra measured near central rapidity in the range 0.5<p_{T}<20 GeV/c exhibit a weak pseudorapidity dependence. The nuclear modification factor R_{pPb} is consistent with unity for p_{T} above 2 GeV/c. This measurement indicates that the strong suppression of hadron production at high p_{T} observed in Pb+Pb collisions at the LHC is not due to an initial-state effect. The measurement is compared to theoretical calculations.
  Physical Review Letters 02/2013; 110(8):082302. · 7.37 Impact Factor
• Source

  Available from: Varlen Grabski

  Article: Pseudorapidity Density of Charged Particles in p+Pb Collisions at sqrt[s_{NN}]=5.02 TeV.

  B Abelev, J Adam, D Adamová, A M Adare, M M Aggarwal, G Aglieri Rinella, M Agnello, A G Agocs, A Agostinelli, Z Ahammed, [......], Y Zhou, J Zhu, H Zhu, X Zhu, A Zichichi, A Zimmermann, G Zinovjev, Y Zoccarato, M Zynovyev, M Zyzak
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  ABSTRACT: The charged-particle pseudorapidity density measured over four units of pseudorapidity in nonsingle-diffractive p+Pb collisions at a center-of-mass energy per nucleon pair sqrt[s_{NN}]=5.02 TeV is presented. The average value at midrapidity is measured to be 16.81±0.71 (syst), which corresponds to 2.14±0.17 (syst) per participating nucleon, calculated with the Glauber model. This is 16% lower than in nonsingle-diffractive pp collisions interpolated to the same collision energy and 84% higher than in d+Au collisions at sqrt[s_{NN}]=0.2 TeV. The measured pseudorapidity density in p+Pb collisions is compared to model predictions and provides new constraints on the description of particle production in high-energy nuclear collisions.
  Physical Review Letters 01/2013; 110(3):032301. · 7.37 Impact Factor
• Article: Charge separation relative to the reaction plane in Pb-Pb collisions at sqrt[s_{NN}]=2.76 TeV.

  B Abelev, J Adam, D Adamová, A M Adare, M M Aggarwal, G Aglieri Rinella, A G Agocs, A Agostinelli, S Aguilar Salazar, Z Ahammed, [......], D Zhou, F Zhou, J Zhu, X Zhu, A Zichichi, A Zimmermann, G Zinovjev, Y Zoccarato, M Zynovyev, M Zyzak
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  ABSTRACT: Measurements of charge-dependent azimuthal correlations with the ALICE detector at the LHC are reported for Pb-Pb collisions at sqrt[s_{NN}]=2.76 TeV. Two- and three-particle charge-dependent azimuthal correlations in the pseudorapidity range |η|<0.8 are presented as a function of the collision centrality, particle separation in pseudorapidity, and transverse momentum. A clear signal compatible with a charge-dependent separation relative to the reaction plane is observed, which shows little or no collision energy dependence when compared to measurements at RHIC energies. This provides a new insight for understanding the nature of the charge-dependent azimuthal correlations observed at RHIC and LHC energies.
  Physical Review Letters 01/2013; 110(1):012301. · 7.37 Impact Factor
• Article: Measurement of the Cross Section for Electromagnetic Dissociation with Neutron Emission in Pb-Pb Collisions at sqrt[s_{NN}]=2.76 TeV.

  B Abelev, J Adam, D Adamová, A M Adare, M M Aggarwal, G Aglieri Rinella, A G Agocs, A Agostinelli, S Aguilar Salazar, Z Ahammed, [......], D Zhou, F Zhou, Y Zhou, J Zhu, X Zhu, A Zichichi, A Zimmermann, G Zinovjev, Y Zoccarato, M Zynovyev
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  ABSTRACT: The first measurement of neutron emission in electromagnetic dissociation of ^{208}Pb nuclei at the LHC is presented. The measurement is performed using the neutron zero degree calorimeters of the ALICE experiment, which detect neutral particles close to beam rapidity. The measured cross sections of single and mutual electromagnetic dissociation of Pb nuclei at sqrt[s_{NN}]=2.76 TeV with neutron emission are σ_{singleEMD}=187.4±0.2(stat)_{-11.2}^{+13.2}(syst) b and σ_{mutualEMD}=5.7±0.1(stat)±0.4(syst) b, respectively. The experimental results are compared to the predictions from a relativistic electromagnetic dissociation model.
  Physical Review Letters 12/2012; 109(25):252302. · 7.37 Impact Factor
• Source

  Available from: C. Oppedisano

  Article: Pion, Kaon, and Proton Production in Central Pb-Pb Collisions at sqrt[s_{NN}]=2.76 TeV.

  B Abelev, J Adam, D Adamová, A M Adare, M M Aggarwal, G Aglieri Rinella, A G Agocs, A Agostinelli, S Aguilar Salazar, Z Ahammed, [......], Y Zhou, F Zhou, J Zhu, X Zhu, A Zichichi, A Zimmermann, G Zinovjev, Y Zoccarato, M Zynovyev, M Zyzak
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  ABSTRACT: In this Letter we report the first results on π^{±}, K^{±}, p, and p[over ¯] production at midrapidity (|y|<0.5) in central Pb-Pb collisions at sqrt[s_{NN}]=2.76 TeV, measured by the ALICE experiment at the LHC. The p_{T} distributions and yields are compared to previous results at sqrt[s_{NN}]=200 GeV and expectations from hydrodynamic and thermal models. The spectral shapes indicate a strong increase of the radial flow velocity with sqrt[s_{NN}], which in hydrodynamic models is expected as a consequence of the increasing particle density. While the K/π ratio is in line with predictions from the thermal model, the p/π ratio is found to be lower by a factor of about 1.5. This deviation from thermal model expectations is still to be understood.
  Physical Review Letters 12/2012; 109(25):252301. · 7.37 Impact Factor
• Article: SU-E-T-311: Dose Perturbation Due to Thin Layers of High-Z in HDR Ir-192 Source Dose Delivery.

  H Zhang, I Das
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  ABSTRACT: Purpose: To evaluate the dose perturbation associated with thin layers of high-Z materials in HDR 192I source dose delivery through Monte Carlo simulation and experimental measurement. Methods: Dose perturbation of high-Z thin materials in HDR 192Ir source dose delivery was experimentally and theoretically studied. MCNP5 Monte Carlo simulation code was employed to calculate the dose enhancement effects at upstream and downstream of high-Z materials. The cutoff energy for photon was 1 keV and for electron 5 keV. A parallel plate ion chamber with window thickness of 0.9 mm, was used to measure the dose rates at the downstream of the high-Z thin layer. The high-Z layer was positioned at 0.625 cm from the 192Ir source. The thickness of layer was from 0.1 to 1 mm. The results were normalized by the dose rate in a homogeneous water phantom at the location of the interface. The high-Z materials used were lead, tin and titanium. In addition, the dose enhancement effects of different high-Z materials at the shortest distance from the interface were also calculated and measured to examine the Z dependence. Results: The Monte Carlo simulation results agreed very well with the experimental data. At the surface of the 0.1 mm high-Z interface, Ti, Sn and Pb respectively increase dose rate by 1.2, 1.4 and 2.5 times the dose rate in homogeneous water medium. The dose rate enhancement depends on Z and thickness of the high-Z layer. The dose enhancement increases with Z. However, an increased thickness in the high- Z layer results in less dose enhancement due to attenuation. Conclusions: HDR 192Ir source dose enhancement by a high-Z material thin layer is similar to that reported from a kilo-voltage X-ray beam. Attention should be paid for high-Z thin layers with HDR source clinically as it could cause significant dose enhancement.
  Medical Physics 06/2012; 39(6):3775. · 2.83 Impact Factor
• Article: SU-E-T-230: Field Factor Verification in Small Fields.

  Y Jia, H Zhang, C Desrosiers, I Das
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  ABSTRACT: Purpose: Small field is being commonly used in radiosurgery and IMRT, however dosimetry is challenging due to source size, electronic disequilibrium and detector size. Correction factor, K, has been published for a limited set of detectors and beam energies. Validity of K for several detectors is investigated. Also extrapolation ion chamber could be used using reciprocity theorem for small fields which is attempted in this study. Methods: Various small volume detectors: IBA SFD, PTW TN60012 diode, and PTW Pinpoint N31006, Standard Imaging A16, along with Nuclear Associate N2339IT extrapolation chamber were used to measure output of square fields from 1×1 to 10×10 cm(2) for Varian 6 and 16 MV beams. Measurements were made in a water phantom at 1.5cm depth for 6MV photon and 3.0cm depth for 15MV photon with SSD 100cm. Extrapolation chamber was used in solid water. Published correction factors (Francescon et al, MP, 2011)1, K were used for the detectors used in this study. The K value was derived for extrapolation chamber by modeling based on the difference between its detector output and the average output factor from the diodes and pinpoints. Results: The variation in output as measured from different detector is significant (±7.0%) for field sizes = 3×3 cm(2) and converges after large field sizes for both energies. The output factor for the extrapolation chamber was out of range from diodes/pinpoints in both 6MV and 16 MV beams. After applying detector K, the field size factors agree each other within ±2.2% for all field sizes. Conclusions: The value of K provides reasonably good data for field factors irrespective of detector and the field factors can be matched within 2.2%. A mathematical function for extrapolation chamber also provides field factors comparable to the other detectors.
  Medical Physics 06/2012; 39(6):3756. · 2.83 Impact Factor
• Source

  Available from: Varlen Grabski

  Article: J/ψ production as a function of charged particle multiplicity in pp collisions at s =7 TeV

  ALICE Collaboration, B. Abelev, J. Adam, D. Adamová, A. M. Adare, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, A. Agostinelli, S. Aguilar Salazar, [......], X. Zhang, Y. Zhou, D. Zhou, F. Zhou, X. Zhu, A. Zichichi, A. Zimmermann, G. Zinovjev, Y. Zoccarato, M. Zynovyev
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  ABSTRACT: The ALICE Collaboration reports the measurement of the relative J/ψ yield as a function of charged particle pseudorapidity density dNch/dη in pp collisions at s=7 TeV at the LHC. J/ψ particles are detected for pt>0, in the rapidity interval |y|<0.9 via decay into e+e-, and in the interval 2.5<y<4.0 via decay into μ+μ- pairs. An approximately linear increase of the J/ψ yields normalized to their event average (dN/dy)/<dN/dy> with (dNch/dη)/<dNch/dη> is observed in both rapidity ranges, where dNch/dη is measured within |η|<1 and pt>0. In the highest multiplicity interval with <dNch/dη(bin)>=24.1, corresponding to four times the minimum bias multiplicity density, an enhancement relative to the minimum bias J/ψ yield by a factor of about 5 at 2.5<y<4 (8 at |y|<0.9) is observed.
  Physics Letters B 05/2012; 712:165-175. · 3.95 Impact Factor
• Article: Asymptomatic transmission of Treponema pallidum (syphilis) through deceased donor liver transplantation.

  L Tariciotti, I Das, L Dori, M T P R Perera, S R Bramhall
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  ABSTRACT: A 55-year-old woman underwent liver transplantation (LT) with a graft from a deceased donor. Mandatory pre-donation investigations showed positive syphilis serology that was available only after the transplant, with high Treponema pallidum particle agglutination assay titer compatible with donor syphilis infection. Despite the institution of appropriate post-exposure prophylaxis, the recipient demonstrated latent seroconversion; however, liver graft function improved without evidence of syphilitic hepatitis or other manifestations of the disease. Through this first reported case of asymptomatic transmission of syphilis following LT, we highlight the investigations and treatment strategies for donor-derived syphilis in liver transplant recipients. This report supplements the existing limited evidence on safe use of infected grafts from syphilitic donors through appropriate post-exposure prophylaxis.
  Transplant Infectious Disease 05/2012; 14(3):321-5. · 2.22 Impact Factor
• Article: High voltage characteristic of large area cathode pad chambers for muon spectrometer of ALICE

  M. Danish Azmi, S. Bose, S. Chattopadhyay, D. Das, I. Das, M. Irfan, S. Das, I. A. Khan, S. Pal, L. Das, B. C. Sinha, T. Sinha
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  ABSTRACT: Large area Cathode Pad Chambers (CPC) with inner and outer radii of 23.7 cm and 117 cm respectively have been fabricated and tested for 2nd Tracking station of Muon Spectrometer of ALICE. The active area of this detector has a radiation length of less than 2 % and the frames are fabricated with Peek GF-30. The anode wire plane consists of 474 anode wires of which 53 % have lengths greater than 1 meter. The separation between the wire plane and the grounded cathode plane is 2.5 mm. The high voltage behaviour of the chamber have been tested under two situations. – With no support below the wires to reduce sagging of long wires. – With a G10 strip-support whose dimension is 950 mm × 2 mm × 2.4 mm. The High Voltage (HV) tests show that a better stability is achieved when the strip support is implemented. Therefore this solution has been adopted for operation in ALICE. KeywordsLHC–ALICE–2nd Tracking Station–CPC–MIP Particles
  Indian Journal of Physics and Proceedings of the Indian Association for the Cultivation of Science -New Series- 05/2012; 84(12):1683-1687. · 0.38 Impact Factor
• Source

  Available from: Varlen Grabski

  Article: First proton–proton collisions at the LHC as observed with the ALICE detector: measurement of the charged-particle pseudorapidity density at GeV

  The ALICE Collaboration, K. Aamodt, N. Abel, U. Abeysekara, A. Abrahantes Quintana, A. Acero, D. Adamová, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, [......], X. Zhang, D. Zhou, S. Zhou, J. Zhu, A. Zichichi, A. Zinchenko, G. Zinovjev, M. Zinovjev, Y. Zoccarato, V. Zycháček
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  ABSTRACT: On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), two counter-rotating proton bunches were circulated for the first time concurrently in the machine, at the LHC injection energy of 450GeV per beam. Although the proton intensity was very low, with only one pilot bunch per beam, and no systematic attempt was made to optimize the collision optics, all LHC experiments reported a number of collision candidates. In the ALICE experiment, the collision region was centred very well in both the longitudinal and transverse directions and 284 events were recorded in coincidence with the two passing proton bunches. The events were immediately reconstructed and analyzed both online and offline. We have used these events to measure the pseudorapidity density of charged primary particles in the central region. In the range |η|<0.5, we obtain dN ch/dη=3.10±0.13(stat.)±0.22(syst.) for all inelastic interactions, and dN ch/dη=3.51±0.15(stat.)±0.25(syst.) for non-single diffractive interactions. These results are consistent with previous measurements in proton–antiproton interactions at the same centre-of-mass energy at the CERN Sp [`(p)]\overline{\mathrm{p}} S collider. They also illustrate the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase.
  European Physical Journal C 04/2012; 65(1):111-125. · 3.63 Impact Factor
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  Available from: Daniel Felea

  Article: Production of pions, kaons and protons in pp collisions at with ALICE at the LHC

  The ALICE Collaboration, K. Aamodt, N. Abel, U. Abeysekara, A. Abrahantes Quintana, A. Abramyan, D. Adamová, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, [......], X. Zhang, D. Zhou, S. Zhou, J. Zhu, A. Zichichi, A. Zinchenko, G. Zinovjev, Y. Zoccarato, V. Zycháček, M. Zynovyev
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  ABSTRACT: The production of π +, π −, K+, K−, p, and [`(p)]\overline{\mathrm{p}} at mid-rapidity has been measured in proton-proton collisions at Ös = 900GeV\sqrt{s} = 900~\mathrm{GeV} with the ALICE detector. Particle identification is performed using the specific energy loss in the inner tracking silicon detector and the time projection chamber. In addition, time-of-flight information is used to identify hadrons at higher momenta. Finally, the distinctive kink topology of the weak decay of charged kaons is used for an alternative measurement of the kaon transverse momentum (p t) spectra. Since these various particle identification tools give the best separation capabilities over different momentum ranges, the results are combined to extract spectra from p t=100MeV/c to 2.5 GeV/c. The measured spectra are further compared with QCD-inspired models which yield a poor description. The total yields and the mean p t are compared with previous measurements, and the trends as a function of collision energy are discussed.
  European Physical Journal C 04/2012; 71(6):1-22. · 3.63 Impact Factor
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  Available from: Vladimir Peskov

  Article: Strange particle production in proton–proton collisions at with ALICE at the LHC

  K. Aamodt, A. Abrahantes Quintana, D. Adamová, A. M. Adare, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, S. Aguilar Salazar, Z. Ahammed, N. Ahmad, [......], P. Zelnicek, A. Zenin, I. Zgura, M. Zhalov, X. Zhang, D. Zhou, A. Zichichi, G. Zinovjev, Y. Zoccarato, M. Zynovyev
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  ABSTRACT: The production of mesons containing strange quarks ($\mbox {$\mbox {, φ) and both singly and doubly strange baryons ($\mbox {$\mbox {, $\mbox {$\mbox {, and $\mbox {$\mbox {) are measured at mid-rapidity in pp collisions at _boxclose_boxclose_boxclose\sqrt{s}=0.9TeV{\rm TeV} with the ALICE experiment at the LHC. The results are obtained from the analysis of about 250k minimum bias events recorded in 2009. Measurements of yields (dN/dy) and transverse momentum spectra at mid-rapidity for inelastic pp collisions are presented. For mesons, we report yields (〈dN/dy〉) of 0.184±0.002(stat.)±0.006(syst.) for $\mbox {$\mbox { and 0.021±0.004(stat.)±0.003(syst.) forφ. For baryons, we find 〈dN/dy〉=0.048±0.001(stat.)±0.004(syst.) for $\mbox {$\mbox {, 0.047±0.002(stat.)±0.005(syst.) for $\mbox {$\mbox { and 0.0101±0.0020(stat.)±0.0009(syst.) for $\mbox {$\mbox {. The results are also compared with predictions for identified particle spectra from QCD-inspired models and provide a baseline for comparisons with both future pp measurements at higher energies and heavy-ion collisions.
  European Physical Journal C 04/2012; 71(3):1-24. · 3.63 Impact Factor
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  Available from: Varlen Grabski

  Article: Charged-particle multiplicity measurement in proton–proton collisions at and 2.36 TeV with ALICE at LHC

  The ALICE Collaboration, K. Aamodt, N. Abel, U. Abeysekara, A. Abrahantes Quintana, A. Abramyan, D. Adamová, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, [......], X. Zhang, D. Zhou, S. Zhou, J. Zhu, A. Zichichi, A. Zinchenko, G. Zinovjev, Y. Zoccarato, V. Zycháček, M. Zynovyev
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  ABSTRACT: Charged-particle production was studied in proton–proton collisions collected at the LHC with the ALICE detector at centre-of-mass energies 0.9TeV and 2.36TeV in the pseudorapidity range |η|<1.4. In the central region (|η|<0.5), at 0.9TeV, we measure charged-particle pseudorapidity density dNch/dh = 3.02±0.01(stat.)+0.08-0.05(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=3.02\pm 0.01(\mathit{stat.})^{+0.08}_{-0.05}(\mathit{syst.}) for inelastic interactions, and dNch/dh = 3.58±0.01(stat.)+0.12-0.12(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=3.58\pm0.01(\mathit{stat.})^{+0.12}_{-0.12}(\mathit{syst.}) for non-single-diffractive interactions. At 2.36TeV, we find dNch/dh = 3.77±0.01(stat.)+0.25-0.12(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=3.77\pm0.01(\mathit{stat.})^{+0.25}_{-0.12}(\mathit{syst.}) for inelastic, and dNch/dh = 4.43±0.01(stat.)+0.17-0.12(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=4.43\pm0.01(\mathit{stat.})^{+0.17}_{-0.12}(\mathit{syst.}) for non-single-diffractive collisions. The relative increase in charged-particle multiplicity from the lower to higher energy is 24.7%±0.5%(stat.)+5.7-2.8%(syst.)24.7\%\pm0.5\%(\mathit{stat.})^{+5.7}_{-2.8}\%(\mathit{syst.}) for inelastic and 23.7%±0.5%(stat.)+4.6-1.1%(syst.)23.7\%\pm0.5\%(\mathit{stat.})^{+4.6}_{-1.1}\%(\mathit{syst.}) for non-single-diffractive interactions. This increase is consistent with that reported by the CMS collaboration for non-single-diffractive events and larger than that found by a number of commonly used models. The multiplicity distribution was measured in different pseudorapidity intervals and studied in terms of KNO variables at both energies. The results are compared to proton–antiproton data and to model predictions.
  European Physical Journal C 04/2012; 68(1):89-108. · 3.63 Impact Factor
• Article: Inclusive J/psi production in pp collisions at sqrt(s) = 2.76 TeV

  ALICE Collaboration, B. Abelev, J. Adam, D. Adamova, A. M. Adare, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, A. Agostinelli, S. Aguilar Salazar, [......], X. Zhang, D. Zhou, Y. Zhou, F. Zhou, X. Zhu, A. Zichichi, A. Zimmermann, G. Zinovjev, Y. Zoccarato, M. Zynovyev
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  ABSTRACT: The ALICE Collaboration has measured inclusive J/psi production in pp collisions at a center of mass energy sqrt(s)=2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges |y|<0.9 and 2.5<y<4 and have been obtained by measuring the electron and muon pair decay channels, respectively. The integrated luminosities for the two channels are L^e_int=1.1 nb^-1 and L^mu_int=19.9 nb^-1, and the corresponding signal statistics are N_J/psi^e+e-=59 +/- 14 and N_J/psi^mu+mu-=1364 +/- 53. We present dsigma_J/psi/dy for the two rapidity regions under study and, for the forward-y range, d^2sigma_J/psi/dydp_t in the transverse momentum domain 0<p_t<8 GeV/c. The results are compared with previously published results at sqrt(s)=7 TeV and with theoretical calculations.
  03/2012;
• Article: Suppression of high transverse momentum D mesons in central Pb--Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV

  ALICE Collaboration, B. Abelev, J. Adam, D. Adamová, A. M. Adare, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, A. Agostinelli, S. Aguilar Salazar, [......], D. Zhou, F. Zhou, Y. Zhou, X. Zhu, J. Zhu, A. Zichichi, A. Zimmermann, G. Zinovjev, Y. Zoccarato, M. Zynovyev
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  ABSTRACT: The production of the prompt charm mesons $D^0$, $D^+$, $D^{*+}$, and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at the LHC, at a centre-of-mass energy $\sqrt{s_{NN}}=2.76$ TeV per nucleon--nucleon collision. The $\pt$-differential production yields in the range $2<p_t<16$ GeV/c at central rapidity, $|y|<0.5$, were used to calculate the nuclear modification factor $R_{AA}$ with respect to a proton-proton reference obtained from the cross section measured at $\sqrt{s}=7$ TeV and scaled to $\sqrt{s}=2.76$ TeV. For the three meson species, $R_{AA}$ shows a suppression by a factor 3-4, for transverse momenta larger than 5 GeV/c in the 20% most central collisions. The suppression is reduced for peripheral collisions.
  03/2012;
• Article: Particle-yield modification in jetlike azimuthal dihadron correlations in Pb-Pb collisions at √s(NN)=2.76 TeV.

  K Aamodt, B Abelev, A Abrahantes Quintana, D Adamová, A M Adare, M M Aggarwal, G Aglieri Rinella, A G Agocs, A Agostinelli, S Aguilar Salazar, [......], X Zhang, D Zhou, F Zhou, Y Zhou, X Zhu, A Zichichi, A Zimmermann, G Zinovjev, Y Zoccarato, M Zynovyev
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  ABSTRACT: The yield of charged particles associated with high-p(t) trigger particles (8<p(t)<15 GeV/c) is measured with the ALICE detector in Pb-Pb collisions at √s(NN)=2.76 TeV relative to proton-proton collisions at the same energy. The conditional per-trigger yields are extracted from the narrow jetlike correlation peaks in azimuthal dihadron correlations. In the 5% most central collisions, we observe that the yield of associated charged particles with transverse momenta p(t)>3 GeV/c on the away side drops to about 60% of that observed in pp collisions, while on the near side a moderate enhancement of 20%-30% is found.
  Physical Review Letters 03/2012; 108(9):092301. · 7.37 Impact Factor
• Article: J/ψ polarization in pp collisions at √s=7 TeV.

  B Abelev, A Abrahantes Quintana, D Adamová, A M Adare, M M Aggarwal, G Aglieri Rinella, A G Agocs, A Agostinelli, S Aguilar Salazar, Z Ahammed, [......], X Zhang, F Zhou, D Zhou, Y Zhou, X Zhu, A Zichichi, A Zimmermann, G Zinovjev, Y Zoccarato, M Zynovyev
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  ABSTRACT: The ALICE Collaboration has studied J/ψ production in pp collisions at √s=7 TeV at the LHC through its muon pair decay. The polar and azimuthal angle distributions of the decay muons were measured, and results on the J/ψ polarization parameters λ(θ) and λ(φ) were obtained. The study was performed in the kinematic region 2.5<y<4, 2<p(t)<8 GeV/c, in the helicity and Collins-Soper reference frames. In both frames, the polarization parameters are compatible with zero, within uncertainties.
  Physical Review Letters 02/2012; 108(8):082001. · 7.37 Impact Factor
• Article: J/ψ Polarization in pp Collisions at s=7TeV

  B. Abelev, A. Abrahantes Quintana, D. Adamová, A. M. Adare, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, A. Agostinelli, S. Aguilar Salazar, Z. Ahammed, [......], X. Zhang, F. Zhou, D. Zhou, Y. Zhou, X. Zhu, A. Zichichi, A. Zimmermann, G. Zinovjev, Y. Zoccarato, M. Zynovyev
  [show abstract] [hide abstract]
  ABSTRACT: The ALICE Collaboration has studied J/ψ production in pp collisions at s=7TeV at the LHC through its muon pair decay. The polar and azimuthal angle distributions of the decay muons were measured, and results on the J/ψ polarization parameters λθ and λϕ were obtained. The study was performed in the kinematic region 2.5<y<4, 2<pt<8GeV/c, in the helicity and Collins-Soper reference frames. In both frames, the polarization parameters are compatible with zero, within uncertainties.
  Physical Review Letters 01/2012; 108(8):82001. · 7.37 Impact Factor
• Article: Heavy flavour decay muon production at forward rapidity in proton-proton collisions at s=7 TeV

  ALICE Collaboration, B. Abelev, J. Adam, D. Adamová, A. M. Adare, M. M. Aggarwal, G. Aglieri Rinella, A. G. Agocs, A. Agostinelli, S. Aguilar Salazar, [......], X. Zhang, Y. Zhou, D. Zhou, F. Zhou, X. Zhu, A. Zichichi, A. Zimmermann, G. Zinovjev, Y. Zoccarato, M. Zynovyev
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  ABSTRACT: The production of muons from heavy flavour decays is measured at forward rapidity in proton-proton collisions at s=7 TeV collected with the ALICE experiment at the LHC. The analysis is carried out on a data sample corresponding to an integrated luminosity L=16.5 nb. The transverse momentum and rapidity differential production cross sections of muons from heavy flavour decays are measured in the rapidity range 2.5<y<4, over the transverse momentum range 2<p<12 GeV/c. The results are compared to predictions based on perturbative QCD calculations.
  Physics Letters B 01/2012; 708:265-275. · 3.95 Impact Factor