Prof Subir Sarkar: Publications

IceCube

IceCube at Oxford

I am a member since 2004 of the IceCube collaboration which discovered cosmic high energy neutrinos and identified some of their astrophysical sources.

IceCube @ Oxford

The integrated Sachs-Wolfe imprints of cosmic superstructures: a problem for ΛCDM

ArXiv 1109.4126 (2011)

Authors:

Seshadri Nadathur, Shaun Hotchkiss, Subir Sarkar

Abstract:

A crucial diagnostic of the ΛCDM cosmological model is the integrated Sachs-Wolfe (ISW) effect of large-scale structure on the cosmic microwave background (CMB). The ISW imprint of superstructures of size \sim100\;h^{-1} Mpc at redshift $z\sim0.5$ has been detected with $>4σ$ significance, however it has been noted that the signal is much larger than expected. We revisit the calculation using linear theory predictions in ΛCDM cosmology for the number density of superstructures and their radial density profile, and take possible selection effects into account. While our expected signal is larger than previous estimates, it is still inconsistent by $>3σ$ with the observation. If the observed signal is indeed due to the ISW effect then huge, extremely underdense voids are far more common in the observed universe than predicted by ΛCDM.

The integrated Sachs-Wolfe imprints of cosmic superstructures: a problem for \Lambda CDM

(2011)

Authors:

Seshadri Nadathur, Shaun Hotchkiss, Subir Sarkar

Observation of an Anisotropy in the Galactic Cosmic Ray arrival direction at 400 TeV with IceCube

ArXiv 1109.1017 (2011)

Authors:

IceCube Collaboration, R Abbasi, Y Abdou, T Abu-Zayyad, M Ackermann, J Adams, JA Aguilar, M Ahlers, MM Allen, D Altmann, K Andeen, J Auffenberg, X Bai, M Baker, SW Barwick, R Bay, JL Bazo Alba, K Beattie, JJ Beatty, S Bechet, JK Becker, K-H Becker, ML Benabderrahmane, S BenZvi, J Berdermann, P Berghaus, D Berley, E Bernardini, D Bertrand, DZ Besson, D Bindig, M Bissok, E Blaufuss, J Blumenthal, DJ Boersma, C Bohm, D Bose, S Böser, O Botner, AM Brown, S Buitink, KS Caballero-Mora, M Carson, D Chirkin, B Christy, F Clevermann, S Cohen, C Colnard, DF Cowen, AH Cruz Silva, MV D'Agostino, M Danninger, J Daughhetee, JC Davis, C De Clercq, T Degner, L Demirörs, F Descamps, P Desiati, G de Vries-Uiterweerd, T DeYoung, JC Díaz-Vélez, M Dierckxsens, J Dreyer, JP Dumm, M Dunkman, J Eisch, RW Ellsworth, O Engdegård, S Euler, PA Evenson, O Fadiran, AR Fazely, A Fedynitch, J Feintzeig, T Feusels, K Filimonov, C Finley, T Fischer-Wasels, BD Fox, A Franckowiak, R Franke, TK Gaisser, J Gallagher, L Gerhardt, L Gladstone, T Glüsenkamp, A Goldschmidt, JA Goodman, D Góra, D Grant, T Griesel, A Groß, S Grullon, M Gurtner, C Ha, A Haj Ismail, A Hallgren, F Halzen, K Han, K Hanson, D Heinen, K Helbing, R Hellauer, S Hickford, GC Hill, KD Hoffman, B Hoffmann, A Homeier, K Hoshina, W Huelsnitz, J-P Hülß, PO Hulth, K Hultqvist, S Hussain, A Ishihara, E Jacobi, J Jacobsen, GS Japaridze, H Johansson, K-H Kampert, A Kappes, T Karg, A Karle, P Kenny, J Kiryluk, F Kislat, SR Klein, J-H Köhne, G Kohnen, H Kolanoski, L Köpke, S Kopper, DJ Koskinen, M Kowalski, T Kowarik, M Krasberg, G Kroll, N Kurahashi, T Kuwabara, M Labare, K Laihem, H Landsman, MJ Larson, R Lauer, J Lünemann, J Madsen, A Marotta, R Maruyama, K Mase, HS Matis, K Meagher, M Merck, P Mészáros, T Meures, S Miarecki, E Middell, N Milke, J Miller, T Montaruli, R Morse, SM Movit, R Nahnhauer, JW Nam, U Naumann, DR Nygren, S Odrowski, A Olivas, M Olivo, A O'Murchadha, S Panknin, L Paul, C Pérez de los Heros, J Petrovic, A Piegsa, D Pieloth, R Porrata, J Posselt, CC Price, PB Price, GT Przybylski, K Rawlins, P Redl, E Resconi, W Rhode, M Ribordy, M Richman, JP Rodrigues, F Rothmaier, C Rott, T Ruhe, D Rutledge, B Ruzybayev, D Ryckbosch, H-G Sander, M Santander, S Sarkar, K Schatto, T Schmidt, A Schönwald, A Schukraft, A Schultes, O Schulz, M Schunck, D Seckel, B Semburg, SH Seo, Y Sestayo, S Seunarine, A Silvestri, GM Spiczak, C Spiering, M Stamatikos, T Stanev, T Stezelberger, RG Stokstad, A Stößl, EA Strahler, R Ström, M Stüer, GW Sullivan, Q Swillens, H Taavola, I Taboada, A Tamburro, A Tepe, S Ter-Antonyan, S Tilav, PA Toale, S Toscano, D Tosi, N van Eijndhoven, J Vandenbroucke, A Van Overloop, J van Santen, M Vehring, M Voge, C Walck, T Waldenmaier, M Wallraff, M Walter, Ch Weaver, C Wendt, S Westerhoff, N Whitehorn, K Wiebe, CH Wiebusch, DR Williams, R Wischnewski, H Wissing, M Wolf, TR Wood, K Woschnagg, C Xu, DL Xu, XW Xu, JP Yanez, G Yodh, S Yoshida, P Zarzhitsky, M Zoll

Abstract:

In this paper we report the first observation in the Southern hemisphere of an energy dependence in the Galactic cosmic ray anisotropy up to a few hundred TeV. This measurement was performed using cosmic ray induced muons recorded by the partially deployed IceCube observatory between May 2009 and May 2010. The data include a total of 33$\times 10^{9}$ muon events with a median angular resolution of $\sim3^{\circ}$ degrees. A sky map of the relative intensity in arrival direction over the Southern celestial sky is presented for cosmic ray median energies of 20 and 400 TeV. The same large-scale anisotropy observed at median energies around 20 TeV is not present at 400 TeV. Instead, the high energy skymap shows a different anisotropy structure including a deficit with a post-trial significance of -6.3$σ$. This anisotropy reveals a new feature of the Galactic cosmic ray distribution, which must be incorporated into theories of the origin and propagation of cosmic rays.

Searches for periodic neutrino emission from binary systems with 22 and 40 strings of IceCube

ArXiv 1108.3023 (2011)

Authors:

IceCube Collaboration, R Abbasi, Y Abdou, T Abu-Zayyad, M Ackermann, J Adams, JA Aguilar, M Ahlers, MM Allen, D Altmann, K Andeen, J Auffenberg, X Bai, M Baker, SW Barwick, R Bay, JL Bazo Alba, K Beattie, JJ Beatty, S Bechet, JK Becker, K-H Becker, ML Benabderrahmane, S BenZvi, J Berdermann, P Berghaus, D Berley, E Bernardini, D Bertrand, DZ Besson, D Bindig, M Bissok, E Blaufuss, J Blumenthal, DJ Boersma, C Bohm, D Bose, S Böser, O Botner, AM Brown, S Buitink, KS Caballero-Mora, M Carson, D Chirkin, B Christy, F Clevermann, S Cohen, C Colnard, DF Cowen, AH Cruz Silva, MV D'Agostino, M Danninger, J Daughhetee, JC Davis, C De Clercq, T Degner, L Demirörs, F Descamps, P Desiati, G de Vries-Uiterweerd, T DeYoung, JC Díaz-Vélez, M Dierckxsens, J Dreyer, JP Dumm, M Dunkman, J Eisch, RW Ellsworth, O Engdegård, S Euler, PA Evenson, O Fadiran, AR Fazely, A Fedynitch, J Feintzeig, T Feusels, K Filimonov, C Finley, T Fischer-Wasels, BD Fox, A Franckowiak, R Franke, TK Gaisser, J Gallagher, L Gerhardt, L Gladstone, T Glüsenkamp, A Goldschmidt, JA Goodman, D Góra, D Grant, T Griesel, A Groß, S Grullon, M Gurtner, C Ha, A Haj Ismail, A Hallgren, F Halzen, K Han, K Hanson, D Heinen, K Helbing, R Hellauer, S Hickford, GC Hill, KD Hoffman, B Hoffmann, A Homeier, K Hoshina, W Huelsnitz, J-P Hülß, PO Hulth, K Hultqvist, S Hussain, A Ishihara, E Jacobi, J Jacobsen, GS Japaridze, H Johansson, K-H Kampert, A Kappes, T Karg, A Karle, P Kenny, J Kiryluk, F Kislat, SR Klein, J-H Köhne, G Kohnen, H Kolanoski, L Köpke, S Kopper, DJ Koskinen, M Kowalski, T Kowarik, M Krasberg, G Kroll, N Kurahashi, T Kuwabara, M Labare, K Laihem, H Landsman, MJ Larson, R Lauer, J Lünemann, J Madsen, A Marotta, R Maruyama, K Mase, HS Matis, K Meagher, M Merck, P Mészáros, T Meures, S Miarecki, E Middell, N Milke, J Miller, T Montaruli, R Morse, SM Movit, R Nahnhauer, JW Nam, U Naumann, DR Nygren, S Odrowski, A Olivas, M Olivo, A O'Murchadha, S Panknin, L Paul, C Pérez de los Heros, J Petrovic, A Piegsa, D Pieloth, R Porrata, J Posselt, PB Price, GT Przybylski, K Rawlins, P Redl, E Resconi, W Rhode, M Ribordy, M Richman, JP Rodrigues, F Rothmaier, C Rott, T Ruhe, D Rutledge, B Ruzybayev, D Ryckbosch, H-G Sander, M Santander, S Sarkar, K Schatto, T Schmidt, A Schönwald, A Schukraft, A Schultes, O Schulz, M Schunck, D Seckel, B Semburg, SH Seo, Y Sestayo, S Seunarine, A Silvestri, GM Spiczak, C Spiering, M Stamatikos, T Stanev, T Stezelberger, RG Stokstad, A Stößl, EA Strahler, R Ström, M Stüer, GW Sullivan, Q Swillens, H Taavola, I Taboada, A Tamburro, A Tepe, S Ter-Antonyan, S Tilav, PA Toale, S Toscano, D Tosi, N van Eijndhoven, J Vandenbroucke, A Van Overloop, J van Santen, M Vehring, M Voge, C Walck, T Waldenmaier, M Wallraff, M Walter, Ch Weaver, C Wendt, S Westerhoff, N Whitehorn, K Wiebe, CH Wiebusch, DR Williams, R Wischnewski, H Wissing, M Wolf, TR Wood, K Woschnagg, C Xu, DL Xu, XW Xu, JP Yanez, G Yodh, S Yoshida, P Zarzhitsky, M Zoll

Abstract:

In this paper we present the results of searches for periodic neutrino emission from a catalog of binary systems. Such modulation, observed in the photon flux, would be caused by the geometry of these systems. In the analysis, the period is fixed by these photon observations, while the phase and duration of the neutrino emission are treated as free parameters to be fit with the data. If the emission occurs during ~20% or less of the total period, this analysis achieves better sensitivity than a time-integrated analysis. We use the IceCube data taken from May 31, 2007 to April 5, 2008 with its 22-string configuration, and from April 5, 2008 to May 20, 2009 with its 40-string configuration. No evidence for neutrino emission is found, with the strongest excess occurring for Cygnus X-3 at 2.1 sigma significance after accounting for trials. Neutrino flux upper limits for both periodic and time-integrated emission are provided.

The Lateral Trigger Probability function for the Ultra-High Energy Cosmic Ray Showers detected by the Pierre Auger Observatory

Astroparticle Physics 35 (2011) 266-276

Authors:

TPA Collaboration, P Abreu, M Aglietta, EJ Ahn, IFM Albuquerque, D Allard, I Allekotte, J Allen, P Allison, JA Castillo, J Alvarez-Muñiz, M Ambrosio, A Aminaei, L Anchordoqui, S Andringa, T Antičić, A Anzalone, C Aramo, E Arganda, F Arqueros, H Asorey, P Assis, J Aublin, M Ave, M Avenier, G Avila, T Bäcker, M Balzer, KB Barber, AF Barbosa, R Bardenet, SLC Barroso, B Baughman, J Bäuml, JJ Beatty, BR Becker, KH Becker, A Bellétoile, JA Bellido, S BenZvi, C Berat, X Bertou, PL Biermann, P Billoir, F Blanco, M Blanco, C Bleve, H Blümer, M Boháčová, D Boncioli, C Bonifazi, R Bonino, N Borodai, J Brack, P Brogueira, WC Brown, R Bruijn, P Buchholz, A Bueno, RE Burton, KS Caballero-Mora, L Caramete, R Caruso, A Castellina, O Catalano, G Cataldi, L Cazon, R Cester, J Chauvin, SH Cheng, A Chiavassa, JA Chinellato, A Chou, J Chudoba, RW Clay, MR Coluccia, R Conceição, F Contreras, H Cook, MJ Cooper, J Coppens, A Cordier, S Coutu, CE Covault, A Creusot, A Criss, J Cronin, A Curutiu, S Dagoret-Campagne, R Dallier, S Dasso, K Daumiller, BR Dawson, RMD Almeida, MD Domenico, CD Donato, SJD Jong, GDL Vega, WJMDM Junior, JRTDM Neto, ID Mitri, VD Souza, KDD Vries, G Decerprit, LD Peral, MD Río, O Deligny, H Dembinski, N Dhital, CD Giulio, JC Diaz, MLD Castro, PN Diep, C Dobrigkeit, W Docters, JC D'Olivo, PN Dong, A Dorofeev, JCD Anjos, MT Dova, D D'Urso, I Dutan, J Ebr, R Engel, M Erdmann, CO Escobar, J Espadanal, A Etchegoyen, PFS Luis, IF Tapia, H Falcke, G Farrar, AC Fauth, N Fazzini, AP Ferguson, A Ferrero, B Fick, A Filevich, A Filipčič, S Fliescher, CE Fracchiolla, ED Fraenkel, U Fröhlich, B Fuchs, R Gaior, RF Gamarra, S Gambetta, B García, DG Gámez, D Garcia-Pinto, A Gascon, H Gemmeke, K Gesterling, PL Ghia, U Giaccari, M Giller, H Glass, MS Gold, G Golup, FG Albarracin, MG Berisso, P Gonçalves, D Gonzalez, JG Gonzalez, B Gookin, D Góra, A Gorgi, P Gouffon, SR Gozzini, E Grashorn, S Grebe, N Griffith, M Grigat, AF Grillo, Y Guardincerri, F Guarino, GP Guedes, A Guzman, JD Hague, P Hansen, D Harari, S Harmsma, JL Harton, A Haungs, T Hebbeker, D Heck, AE Herve, C Hojvat, N Hollon, VC Holmes, P Homola, JR Hörandel, A Horneffer, M Hrabovský, T Huege, A Insolia, F Ionita, A Italiano, C Jarne, S Jiraskova, M Josebachuili, K Kadija, KH Kampert, P Karhan, P Kasper, B Kégl, B Keilhauer, A Keivani, JL Kelley, E Kemp, RM Kieckhafer, HO Klages, M Kleifges, J Kleinfeller, J Knapp, D-H Koang, K Kotera, N Krohm, O Krömer, D Kruppke-Hansen, F Kuehn, D Kuempel, JK Kulbartz, N Kunka, GL Rosa, C Lachaud, P Lautridou, MSAB Leão, D Lebrun, P Lebrun, MALD Oliveira, A Lemiere, A Letessier-Selvon, I Lhenry-Yvon, K Link, R López, AL Agüera, K Louedec, JL Bahilo, L Lu, A Lucero, M Ludwig, H Lyberis, MC Maccarone, C Macolino, S Maldera, D Mandat, P Mantsch, AG Mariazzi, J Marin, V Marin, IC Maris, HRM Falcon, G Marsella, D Martello, L Martin, H Martinez, OM Bravo, HJ Mathes, J Matthews, JAJ Matthews, G Matthiae, D Maurizio, PO Mazur, G Medina-Tanco, M Melissas, D Melo, E Menichetti, A Menshikov, P Mertsch, C Meurer, S Mićanović, MI Micheletti, W Miller, L Miramonti, L Molina-Bueno, S Mollerach, M Monasor, DM Ragaigne, F Montanet, B Morales, C Morello, E Moreno, JC Moreno, C Morris, M Mostafá, CA Moura, S Mueller, MA Muller, G Müller, M Münchmeyer, R Mussa, G Navarra, JL Navarro, S Navas, P Necesal, L Nellen, A Nelles, J Neuser, PT Nhung, L Niemietz, N Nierstenhoefer, D Nitz, D Nosek, L Nožka, M Nyklicek, J Oehlschläger, A Olinto, P Oliva, VM Olmos-Gilbaja, M Ortiz, N Pacheco, DP Selmi-Dei, M Palatka, J Pallotta, N Palmieri, G Parente, E Parizot, A Parra, RD Parsons, S Pastor, T Paul, M Pech, J Pękala, R Pelayo, IM Pepe, L Perrone, R Pesce, E Petermann, S Petrera, P Petrinca, A Petrolini, Y Petrov, J Petrovic, C Pfendner, N Phan, R Piegaia, T Pierog, P Pieroni, M Pimenta, V Pirronello, M Platino, VH Ponce, M Pontz, P Privitera, M Prouza, EJ Quel, S Querchfeld, J Rautenberg, O Ravel, D Ravignani, B Revenu, J Ridky, S Riggi, M Risse, P Ristori, H Rivera, V Rizi, J Roberts, C Robledo, WRD Carvalho, G Rodriguez, JR Martino, JR Rojo, I Rodriguez-Cabo, MD Rodríguez-Frías, G Ros, J Rosado, T Rossler, M Roth, B Rouillé-d'Orfeuil, E Roulet, AC Rovero, C Rühle, F Salamida, H Salazar, G Salina, F Sánchez, CE Santo, E Santos, EM Santos, F Sarazin, B Sarkar, S Sarkar, R Sato, N Scharf, V Scherini, H Schieler, P Schiffer, A Schmidt, F Schmidt, O Scholten, H Schoorlemmer, J Schovancova, P Schovánek, F Schröder, S Schulte, D Schuster, SJ Sciutto, M Scuderi, A Segreto, M Settimo, A Shadkam, RC Shellard, I Sidelnik, G Sigl, HHS Lopez, A Śmiałkowski, R Šmída, GR Snow, P Sommers, J Sorokin, H Spinka, R Squartini, S Stanic, J Stapleton, J Stasielak, M Stephan, E Strazzeri, A Stutz, F Suarez, T Suomijärvi, AD Supanitsky, T Šuša, MS Sutherland, J Swain, Z Szadkowski, M Szuba, A Tamashiro, A Tapia, M Tartare, O Taşcău, CGT Ruiz, R Tcaciuc, D Tegolo, NT Thao, D Thomas, J Tiffenberg, C Timmermans, DK Tiwari, W Tkaczyk, CJT Peixoto, B Tomé, A Tonachini, P Travnicek, DB Tridapalli, G Tristram, E Trovato, M Tueros, R Ulrich, M Unger, M Urban, JFV Galicia, I Valiño, L Valore, AMVD Berg, E Varela, BV Cárdenas, JR Vázquez, RA Vázquez, D Veberič, V Verzi, J Vicha, M Videla, L Villaseñor, H Wahlberg, P Wahrlich, O Wainberg, D Warner, AA Watson, M Weber, K Weidenhaupt, A Weindl, S Westerhoff, BJ Whelan, G Wieczorek, L Wiencke, B Wilczyńska, H Wilczyński, M Will, C Williams, T Winchen, MG Winnick, M Wommer, B Wundheiler, T Yamamoto, T Yapici, P Younk, G Yuan, A Yushkov, B Zamorano, E Zas, D Zavrtanik, M Zavrtanik, I Zaw, A Zepeda, MZ Silva, M Ziolkowski

Abstract:

In this paper we introduce the concept of Lateral Trigger Probability (LTP) function, i.e., the probability for an extensive air shower (EAS) to trigger an individual detector of a ground based array as a function of distance to the shower axis, taking into account energy, mass and direction of the primary cosmic ray. We apply this concept to the surface array of the Pierre Auger Observatory consisting of a 1.5 km spaced grid of about 1600 water Cherenkov stations. Using Monte Carlo simulations of ultra-high energy showers the LTP functions are derived for energies in the range between 10^{17} and 10^{19} eV and zenith angles up to 65 degs. A parametrization combining a step function with an exponential is found to reproduce them very well in the considered range of energies and zenith angles. The LTP functions can also be obtained from data using events simultaneously observed by the fluorescence and the surface detector of the Pierre Auger Observatory (hybrid events). We validate the Monte-Carlo results showing how LTP functions from data are in good agreement with simulations.

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