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Measurement of top quark polarization in top-antitop events from proton-proton collisions at √s = 7 TeV using the ATLAS detector

Physical Review Letters 111:23 (2013)

Authors:

G Aad, T Abajyan, B Abbott, J Abdallah, SA Khalek, O Abdinov, R Aben, B Abi, M Abolins, OS Abou-Zeid, H Abramowicz, H Abreu, Y Abulaiti, BS Acharya, L Adamczyk, DL Adams, TN Addy, J Adelman, S Adomeit, T Adye, S Aefsky, T Agatonovic-Jovin, JA Aguilar-Saavedra, M Agustoni, SP Ahlen, A Ahmad, M Ahsan, G Aielli, TPA Ã…kesson, G Akimoto, AV Akimov, MA Alam, J Albert, S Albrand, MJA Verzini, M Aleksa, IN Aleksandrov, F Alessandria, C Alexa, G Alexander, G Alexandre, T Alexopoulos, M Alhroob, M Aliev, G Alimonti, L Alio, J Alison, BMM Allbrooke, LJ Allison, PP Allport, SE Allwood-Spiers, J Almond, A Aloisio, R Alon, A Alonso, F Alonso, A Altheimer, BA Gonzalez, MG Alviggi, K Amako, YA Coutinho, C Amelung, VV Ammosov, SPA Dos Santos, A Amorim, S Amoroso, N Amram, C Anastopoulos, LS Ancu, N Andari, T Andeen, CF Anders, G Anders, KJ Anderson, A Andreazza, V Andrei, XS Anduaga, S Angelidakis, P Anger, A Angerami, F Anghinolfi, AV Anisenkov, N Anjos, A Annovi, A Antonaki, M Antonelli, A Antonov, J Antos, F Anulli, M Aoki, LA Bella, R Apolle, G Arabidze, I Aracena, Y Arai, ATH Arce, S Arfaoui, JF Arguin, S Argyropoulos, E Arik

Abstract:

This Letter presents measurements of the polarization of the top quark in top-antitop quark pair events, using 4:7 fb–1of proton-proton collision data recorded with the ATLAS detector at the Large Hadron Collider at √s = 7 TeV. Final states containing one or two isolated leptons (electrons or muons) and jets are considered. Two measurements of αℓP, the product of the leptonic spin-analyzing power and the top quark polarization, are performed assuming that the polarization is introduced by either a CP conserving or a maximally CP violating production process. The measurements obtained, αℓPCPC=–0.035 ± 0.014(stat) ± 0:037(syst) and αℓPCPV= 0.020 ± 0:016(stat)+0.013–0.017(syst), are in good agreement with the standard model prediction of negligible top quark polarization.

Measuring the transition to homogeneity with photometric redshift surveys

(2013)

Authors:

D Alonso, A Bueno Belloso, FJ Sánchez, J García-Bellido, E Sánchez

The Youngest Known X-ray Binary: Circinus X-1 and its Natal Supernova Remnant

(2013)

Authors:

S Heinz, P Sell, RP Fender, PG Jonker, WN Brandt, DE Calvelo-Santos, AK Tzioumis, MA Nowak, NS Schulz, R Wijnands, M van der Klis

Herschel observations and a model for IRAS 08572+3915: A candidate for the most luminous infrared galaxy in the local (z < 0.2) Universe

Monthly Notices of the Royal Astronomical Society: Letters 437:1 (2013)

Authors:

A Efstathiou, C Pearson, D Farrah, D Rigopoulou, J Gracía-Carpio, A Verma, HWW Spoon, J Afonso, J Bernard-Salas, DL Clements, A Cooray, D Cormier, M Etxaluze, J Fischer, E Gonźalez-Alfonso, P Hurley, V Lebouteiller, SJ Oliver, M Rowan-Robinson, E Sturm

Abstract:

We present Herschel photometry and spectroscopy, carried out as part of the Herschel ultraluminous infrared galaxy (ULIRG) survey, and a model for the infrared to submillimetre emission of the ULIRG IRAS 08572+3915. This source shows one of the deepest known silicate absorption features and no polycyclic aromatic hydrocarbon emission. The model suggests that this object is powered by an active galactic nucleus (AGN) with a fairly smooth torus viewed almost edge-on and a very young starburst. According to our model, the AGN contributes about 90 per cent of the total luminosity of 1.1 × 1013 L⊙, which is about a factor of 5 higher than previous estimates. The large correction of the luminosity is due to theanisotropy of the emission of the best-fitting torus. Similar corrections may be necessary for other local and high-z analogues. This correction implies that IRAS 08572+3915 at a redshift of 0.058 35 may be the nearest hyperluminous infrared galaxy and probably the most luminous infrared galaxy in the local (z < 0.2) Universe. IRAS 08572+3915 shows a low ratio of [C II] to IR luminosity (log L[C II]/LIR < -3.8) and a [OI]63 μm to [CII]158 μm line ratio of about 1 that supports the model presented in this Letter ©2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Jet and underlying event properties as a function of charged-particle multiplicity in proton-proton collisions at √s = 7 TeV

European Physical Journal C 73:12 (2013) 1-26

Authors:

S Chatrchyan, V Khachatryan, AM Sirunyan, A Tumasyan, W Adam, T Bergauer, M Dragicevic, J Erö, C Fabjan, M Friedl, R Frühwirth, VM Ghete, N Hörmann, J Hrubec, M Jeitler, W Kiesenhofer, V Knünz, M Krammer, I Krätschmer, D Liko, I Mikulec, D Rabady, B Rahbaran, C Rohringer, H Rohringer, R Schöfbeck, J Strauss, A Taurok, W Treberer-Treberspurg, W Waltenberger, CE Wulz, V Mossolov, N Shumeiko, J Suarez Gonzalez, S Alderweireldt, M Bansal, S Bansal, T Cornelis, EA De Wolf, X Janssen, A Knutsson, S Luyckx, L Mucibello, S Ochesanu, B Roland, R Rougny, Z Staykova, H Van Haevermaet, P Van Mechelen, N Van Remortel, A Van Spilbeeck, F Blekman, S Blyweert, J D'Hondt, A Kalogeropoulos, J Keaveney, S Lowette, M Maes, A Olbrechts, S Tavernier, W Van Doninck, P Van Mulders, GP Van Onsem, I Villella, C Caillol, B Clerbaux, G De Lentdecker, L Favart, APR Gay, T Hreus, A Léonard, PE Marage, A Mohammadi, L Perniè, T Reis, T Seva, L Thomas, C Vander Velde, P Vanlaer, J Wang, V Adler, K Beernaert, L Benucci, A Cimmino, S Costantini, S Dildick, G Garcia, B Klein, J Lellouch, A Marinov, J Mccartin, AA Ocampo Rios, D Ryckbosch, M Sigamani, N Strobbe, F Thyssen, M Tytgat, S Walsh, E Yazgan, N Zaganidis

Abstract:

Characteristics of multi-particle production in proton-proton collisions at √s = 7 TeV are studied as a function of the charged-particle multiplicity, N ch. The produced particles are separated into two classes: those belonging to jets and those belonging to the underlying event. Charged particles are measured with pseudorapidity {pipe}η{pipe}<2.4 and transverse momentum p T>0.25 GeV/c. Jets are reconstructed from charged-particles only and required to have p T>5 GeV/c. The distributions of jet p T, average p T of charged particles belonging to the underlying event or to jets, jet rates, and jet shapes are presented as functions of N ch and compared to the predictions of the pythia and herwig event generators. Predictions without multi-parton interactions fail completely to describe the N ch-dependence observed in the data. For increasing N ch, pythia systematically predicts higher jet rates and harder p T spectra than seen in the data, whereas herwig shows the opposite trends. At the highest multiplicity, the data-model agreement is worse for most observables, indicating the need for further tuning and/or new model ingredients. © 2013 CERN for the benefit of the CMS collaboration.