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Measurement of the charge ratio of atmospheric muons with the CMS detector

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 692:2 (2010) 83-104

Authors:

V Khachatryan, AM Sirunyan, A Tumasyan, W Adam, T Bergauer, M Dragicevic, J Erö, C Fabjan, M Friedl, R Frühwirth, VM Ghete, J Hammer, S Hänsel, M Hoch, N Hörmann, J Hrubec, M Jeitler, G Kasieczka, W Kiesenhofer, M Krammer, D Liko, I Mikulec, M Pernicka, H Rohringer, R Schöfbeck, J Strauss, A Taurok, F Teischinger, W Waltenberger, G Walzel, E Widl, CE Wulz, V Mossolov, N Shumeiko, J Suarez Gonzalez, L Benucci, L Ceard, EA De Wolf, M Hashemi, X Janssen, T Maes, L Mucibello, S Ochesanu, B Roland, R Rougny, M Selvaggi, H Van Haevermaet, P Van Mechelen, N Van Remortel, V Adler, S Beauceron, S Blyweert, J D'Hondt, O Devroede, A Kalogeropoulos, J Maes, M Maes, S Tavernier, W Van Doninck, P Van Mulders, I Villella, EC Chabert, O Charaf, B Clerbaux, G De Lentdecker, V Dero, APR Gay, GH Hammad, PE Marage, C Vander Velde, P Vanlaer, J Wickens, S Costantini, M Grunewald, B Klein, A Marinov, D Ryckbosch, F Thyssen, M Tytgat, L Vanelderen, P Verwilligen, S Walsh, N Zaganidis, S Basegmez, G Bruno, J Caudron, J De Favereau De Jeneret, C Delaere, P Demin, D Favart, A Giammanco, G Grégoire, J Hollar, V Lemaitre, O Militaru, S Ovyn, D Pagano, A Pin, K Piotrzkowski, L Quertenmont

Abstract:

We present a measurement of the ratio of positive to negative muon fluxes from cosmic ray interactions in the atmosphere, using data collected by the CMS detector both at ground level and in the underground experimental cavern at the CERN LHC. Muons were detected in the momentum range from 5 GeV/. c to 1 TeV/. c. The surface flux ratio is measured to be 1.2766±0.0032(stat.)±0.0032(syst.), independent of the muon momentum, below 100 GeV/. c. This is the most precise measurement to date. At higher momenta the data are consistent with an increase of the charge ratio, in agreement with cosmic ray shower models and compatible with previous measurements by deep-underground experiments. © 2010.
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Measurement of the muon stopping power in lead tungstate

Journal of Instrumentation 5:3 (2010)

Authors:

S Chatrchyan, V Khachatryan, AM Sirunyan, W Adam, B Arnold, H Bergauer, T Bergauer, M Dragicevic, M Eichberger, J Erö, M Friedl, R Frühwirth, VM Ghete, J Hammer, S Hansel, M Hoch, N Hörmann, J Hrubec, M Jeitler, G Kasieczka, K Kastner, M Krammer, D Liko, I De Magrans Abril, I Mikulec, F Mittermayr, B Neuherz, M Oberegger, M Padrta, M Pernicka, H Rohringer, S Schmid, R Schöfbeck, T Schreiner, R Stark, H Steininger, J Strauss, A Taurok, F Teischinger, T Themel, D Uhl, P Wagner, W Waltenberger, G Walzel, E Widl, CE Wulz, V Chekhovsky, O Dvornikov, I Emeliantchik, A Litomin, V Makarenko, I Marfin, V Mossolov, N Shumeiko, A Solin, R Stefanovitch, J Suarez Gonzalez, A Tikhonov, A Fedorov, A Karneyeu, M Korzhik, V Panov, R Zuyeuski, P Kuchinsky, W Beaumont, L Benucci, M Cardaci, EA De Wolf, E Delmeire, D Druzhkin, M Hashemi, X Janssen, T Maes, L Mucibello, S Ochesanu, R Rougny, M Selvaggi, H Van Haevermaet, P Van Mechelen, N Van Remortel, V Adler, S Beauceron, S Blyweert, J D'Hondt, S De Weirdt, O Devroede, J Heyninck, A Kalogeropoulos, J Maes, M Maes, MU Mozer, S Tavernier, W Van Doninck, P Van Mulders, I Villella, O Bouhali, EC Chabert, O Charaf, B Clerbaux, G De Lentdecker

Abstract:

A large sample of cosmic ray events collected by the CMS detector is exploited to measure the specific energy loss of muons in the lead tungstate (PbWO4) of the electromagnetic calorimeter. The measurement spans a momentum range from 5 GeV/c to 1 TeV/c. The results are consistent with the expectations over the entire range. The calorimeter energy scale, set with 120 GeV/c electrons, is validated down to the sub-GeV region using energy deposits, of order 100 MeV, associated with low-momentum muons. The muon critical energy in PbWO4 is measured to be 160+5-68 GeV, in agreement with expectations. This is the first experimental determination of muon critical energy. © 2010 IOP Publishing Ltd and SISSA.
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New experiments with antiprotons

Proceedings of Science 120 (2010)

Authors:

DM Kaplan, A Cronin, L Bartoszek, AP Mills, GM Pia-Centino, TJ Phillips, DC Christian, P Derwent, M Fischler, K Gollwitzer, A Hahn, V Papadimitriou, G Stancari, M Stancari, R Stefanski, J Volk, S Werkema, W Wester, HB White, GP Yeh, W Baldini, RG Greaves, SD Howe, GP Jackson, R Lewis, JM Zlotnicki, K Lau, DM Kaplan, TJ Roberts, J Terry, Y Torun, CG White, A Giri, A Drutskoy, GA Horton-Smith, B Ratra, HK Park, O Piskunova, T Holmstrom, TK Pedlar, HR Gustafson, M Merkin, JB Pearson, J Rosen, M Wayne, F Azfar, T Coan, A Chakravorty, MG Raizen, EC Dukes

Abstract:

Fermilab operates the world's most intense antiproton source. Newly proposed experiments can use those antiprotons either parasitically during Tevatron Collider running or after the Tevatron Collider finishes. For example, the annihilation of 8 GeV antiprotons is expected to yield world-leading sensitivities to hyperon rare decays and CP violation. It could also provide the world's most intense source of tagged D0 mesons, and thus the best near-term opportunity to study charm mixing and, via CP violation, to search for new physics. Other precision measurements that could be made include properties of the X(3872) and the charmonium system. An experiment using a Penning trap and an atom interferometer could make the world's first measurement of the gravitational force on antimatter. These and other potential measurements using antiprotons could lead to a broad physics program at Fermilab in the post-Tevatron era.

No evidence for black hole spin powering of jets in X-ray binaries

Monthly Notices of the Royal Astronomical Society 406:3 (2010) 1425-1434

Authors:

RP Fender, E Gallo, D Russell

Abstract:

In this paper, we consider the reported measurements of black hole spin for black hole X-ray binaries and compare them against the measurements of jet power and speed across all accretion states in these systems. We find no evidence for any correlation between the properties of the jets and the reported spin measurements. These constraints are strongest in the hard X-ray state, which is associated with a continuous powerful jet. We are led to conclude that one or more of the following is correct: (i) the calculated jet power and speed measurements are wrong, (ii) the reported spin measurements are wrong and (iii) there is no strong dependence of the jet properties on the black hole spin. In addition to this lack of observational evidence for a relation between the black hole spin and jet properties in stellar mass black holes, we highlight the fact that there appear to be at least three different ways in which the jet power and/or radiative efficiency from a black hole X-ray binary may vary, two of which are certainly independent of spin because they occur in the same source on relatively short time-scales and the third which does not correlate with any reported measurements of black hole spin. We briefly discuss how these findings may impact upon interpretations of populations of active galactic nuclei in the context of black hole spin and merger history. © 2010 The Authors. Journal compilation © 2010 RAS.
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Observation of long-range, near-side angular correlations in proton-proton collisions at the LHC

Journal of High Energy Physics 2010:9 (2010)

Authors:

V Khachatryan, AM Sirunyan, A Tumasyan, W Adam, T Bergauer, M Dragicevic, J Erö, C Fabjan, M Friedl, R Frühwirth, VM Ghete, J Hammer, S Hänsel, C Hartl, M Hoch, N Hörmann, J Hrubec, M Jeitler, G Kasieczka, W Kiesenhofer, M Krammer, D Liko, I Mikulec, M Pernicka, H Rohringer, R Schöfbeck, J Strauss, A Taurok, F Teischinger, W Waltenberger, G Walzel, E Widl, CE Wulz, V Mossolov, N Shumeiko, J Suarez Gonzalez, L Benucci, L Ceard, EA De Wolf, X Janssen, T Maes, L Mucibello, S Ochesanu, B Roland, R Rougny, M Selvaggi, H Van Haevermaet, P Van Mechelen, N Van Remortel, V Adler, S Beauceron, S Blyweert, J D'Hondt, O Devroede, A Kalogeropoulos, J Maes, M Maes, S Tavernier, W Van Doninck, P Van Mulders, I Villella, EC Chabert, O Charaf, B Clerbaux, G De Lentdecker, V Dero, APR Gay, GH Ham-Mad, T Hreus, PE Marage, C Vander Velde, P Vanlaer, J Wickens, S Costantini, M Grunewald, B Klein, A Marinov, D Ryckbosch, F Thyssen, M Tytgat, L Vanelderen, P Verwilligen, S Walsh, N Zaganidis, S Basegmez, G Bruno, J Caudron, J De Favereau De Jeneret, C Delaere, P Demin, D Favart, A Giammanco, G Grégoire, J Hollar, V Lemaitre, O Militaru, S Ovyn, D Pagano, A Pin, K Piotrzkowski

Abstract:

Results on two-particle angular correlations for charged particles emitted in proton-proton collisions at center-of-mass energies of 0.9, 2.36, and 7TeV are presented, using data collected with the CMS detector over a broad range of pseudorapidity (η) and azimuthal angle (φ). Short-range correlations in Δη, which are studied in minimum bias events, are characterized using a simple "independent cluster" parametrization in order to quantify their strength (cluster size) and their extent in η (cluster decay width). Long-range azimuthal correlations are studied differentially as a function of charged particle multiplicity and particle transverse momentum using a 980 nb-1 data set at 7TeV. In high multiplicity events, a pronounced structure emerges in the two-dimensional correlation function for particle pairs with intermediate px of 1-3 GeV/c, 2.0 < |Δη| < 4.8 and Δφ ≈0. This is the first observation of such a long-range, near-side feature in two-particle correlation functions in pp or pp̄ collisions. © SISSA 2010.
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