J.Allen, T.Awes, A.Badal a, S.Baum gart , R.Bellwied, L.Benhabib, C.Bernard, N.Bianchi, F.Blanco, Y.Bortoli, G .Bourdaud, O .Bourrion, B.Boyer, E.Bruna, J.Butterworth, H.Caines, D.Calvo Diaz Aldagalan, G .P.Capitani, Y.Carcagno, A.Casanova Diaz, M .Cherney, G .Conesa Balbastre, T.M .Corm ier, L.Cunqueiro M endez, H.Delagrange, M .DelFranco, M .Dialinas, P.DiNezza, A.Donoghue, M .Elnim r, A.Enokizono, M .Estienne, J.Faivre, A.Fantoni, F.Fichera, B.Foglio, S.Fresneau, J.Fujita, C.Furget, S.G adrat, I.G arishvili, M .G erm ain, N.G iudice, Y.G orbunov, A.G rim aldi, N.G uardone, R.G uernane, C.Hadjidakis, J.Ham blen, J.W .Harris, D.Hasch, M .Heinz, P.T.Hille, D.Hornback, R.Ichou, P.Jacobs, S.Jangal, K .Jayananda, J.L.K lay, A.G .K nospe, S.K ox, J.K ral, P.Laloux, S.LaPointe, P.La Rocca, S.Lewis, Q .Li, F.Librizzi, D.M adagodahettigeDon, I.M artashvili, B.M ayes, T.M illetto, V.M uccifora, H.M uller, J.F.M uraz, C.Nattrass, F.Noto, N.Novitzky, G .O dyniec, A.O rlandi, A.Palm eri, G .S.Pappalardo, A.Pavlinov, W .Pesci, V.Petrov, C.Petta, P.Pichot, L.Pinsky, M .Ploskon, F.Pom pei, A.Pulvirenti, J.Putschke, C.A.Pruneau, J.Rak, J.Rasson, K .F.Read, J.S.Real, A.R.Reolon, F.Riggi, J.Riso, F.Ronchetti, C.Roy, D.Roy, M .Salem i, S.Salur, M .Sharm a, D.Silverm yr, N.Sm irnov, R.Soltz, V.Sparti, J.-S.Stutzm ann, T.J.M .Sym ons, A.Tarazona M artinez, L.Tarini, R.Thom en, A.Tim m ins, M .van Leeuwen, R.Vieira, A.Viticchi e, S.Voloshin, D.W ang, Y.W ang, and R.M .W ard

The inclusive charged particle transverse momentum distribution is measured in proton-proton collisions at root s = 900 GeV at the LHC using the ALICE detector. The measurement is performed in the central pseudorapidity region (vertical bar eta vertical bar < 0.8) over the transverse momentum range 0.15 < p(T) < 10 GeV/c. The correlation between transverse momentum and particle multiplicity is also studied. Results are presented for inelastic (INEL) and non-single-diffractive (NSD) events. The average transverse momentum for vertical bar eta vertical bar < 0.8 is < p(T)>(INEL) = 0.483 +/- 0.001 (stat.) +/- 0.007 (syst.) GeV/c and < p(T)>(NSD) = 0.489 +/- 0.001 (stat.) +/- 0.007 (syst.) GeV/c, respectively. The data exhibit a slightly larger < p(T)> than measurements in wider pseudorapidity intervals. The results are compared to simulations with the Monte Carlo event generators PYTHIA and PHOJET. (C) 2010 Published by Elsevier B.V.

We report on the measurement of two-pion correlation functions from pp collisions at {radical}(s)=900 GeV performed by the ALICE experiment at the Large Hadron Collider. Our analysis shows an increase of the Hanbury Brown-Twiss radius with increasing event multiplicity, in line with other measurements done in particle- and nuclear collisions. Conversely, the strong decrease of the radius with increasing transverse momentum, as observed at the Relativistic Heavy Ion Collider and at Tevatron, is not manifest in our data.

ALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 mu m in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10(5) charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.

The performance of prototypes for the ALICE electromagnetic sampling calorimeter has been studied in test beam measurements at FNAL and CERN. A 4×4 array of final design modules showed an energy resolution of about 11%/E(GeV)⊕1.7% with a uniformity of the response to electrons of 1% and a good linearity in the energy range from 10 to 100GeV. The electromagnetic shower position resolution was found to be described by 1.5mm⊕5.3mm/E(GeV). For an electron identification efficiency of 90% a hadron rejection factor of >600 was obtained.

ALICE (A Large Ion Collider Experiment) at the LHC contains a wide array of detector systems for measuring hadrons, leptons, and photons. ALICE is designed to carry out comprehensive measurements of high energy nucleus-nucleus collisions, in order to study QCD matter under extreme conditions and to study the phase transition between confined matter and the Quark-Gluon Plasma (QGP). Discussion of the full ALICE physics program can be found in [1, 2]. The interaction and energy loss of high energy partons in matter provides a sensitive tomographic probe of the medium generated in high energy nuclear collisions (“jet quenching”) [3–6]. Jet quenching measurements have played a key role at the Relativistic Heavy Ion Collider (RHIC) [7–10] and will be central to the study of nuclear collisions at the LHC. This Technical Design Report describes a large acceptance Electromagnetic Calorimeter (EMCal) that will be installed in the ALICE central detector. The EMCal enhances ALICE's capabilities for jet quenching measurements. The addition of the EMCal enables triggering on high energy jets, reduces significantly the measurement bias for jet quenching studies, improves jet energy resolution, and augments existing ALICE capabilities to measure high momentum photons and electrons. Combined with ALICE's excellent capabilities to track and identify particles from very low pt to high pt the EMCal enables an extensive study of jet quenching at the LHC.