Evidence for a bottom baryon resonance Lambda_b* in CDF data

ArXiv 1308.176 (2013)

Authors:

CDF Collaboration, T Aaltonen, S Amerio, D Amidei, A Anastassov, A Annovi, J Antos, G Apollinari, JA Appel, T Arisawa, A Artikov, J Asaadi, W Ashmanskas, B Auerbach, A Aurisano, F Azfar, W Badgett, T Bae, A Barbaro-Galtieri, VE Barnes, BA Barnett, P Barria, P Bartos, M Bauce, F Bedeschi, S Behari, G Bellettini, J Bellinger, D Benjamin, A Beretvas, A Bhatti, KR Bland, B Blumenfeld, A Bocci, A Bodek, D Bortoletto, J Boudreau, A Boveia, L Brigliadori, C Bromberg, E Brucken, J Budagov, HS Budd, K Burkett, G Busetto, P Bussey, P Butti, A Buzatu, A Calamba, S Camarda, M Campanelli, F Canelli, B Carls, D Carlsmith, R Carosi, S Carrillo, B Casal, M Casarsa, A Castro, P Catastini, D Cauz, V Cavaliere, M Cavalli-Sforza, A Cerri, L Cerrito, YC Chen, M Chertok, G Chiarelli, G Chlachidze, K Cho, D Chokheli, A Clark, C Clarke, ME Convery, J Conway, M Corbo, M Cordelli, CA Cox, DJ Cox, M Cremonesi, D Cruz, J Cuevas, R Culbertson, N d'Ascenzo, M Datta, P de Barbaro, L Demortier, L Marchese, M Deninno, F Devoto, M D'Errico, A Di Canto, B Di Ruzza, JR Dittmann, M D'Onofrio, S Donati, M Dorigo, A Driutti, K Ebina, R Edgar, A Elagin, R Erbacher, S Errede, B Esham, S Farrington, JP Fernández Ramos, R Field, G Flanagan, R Forrest, M Franklin, JC Freeman, H Frisch, Y Funakoshi, C Galloni, AF Garfinkel, P Garosi, H Gerberich, E Gerchtein, S Giagu, V Giakoumopoulou, K Gibson, CM Ginsburg, N Giokaris, P Giromini, G Giurgiu, V Glagolev, D Glenzinski, M Gold, D Goldin, A Golossanov, G Gomez, G Gomez-Ceballos, M Goncharov, O González López, I Gorelov, AT Goshaw, K Goulianos, E Gramellini, S Grinstein, C Grosso-Pilcher, RC Group, J Guimaraes da Costa, SR Hahn, JY Han, F Happacher, K Hara, M Hare, RF Harr, T Harrington-Taber, K Hatakeyama, C Hays, J Heinrich, M Herndon, A Hocker, Z Hong, W Hopkins, S Hou, RE Hughes, U Husemann, M Hussein, J Huston, G Introzzi, M Iori, A Ivanov, E James, D Jang, B Jayatilaka, EJ Jeon, S Jindariani, M Jones, KK Joo, SY Jun, TR Junk, M Kambeitz, T Kamon, PE Karchin, A Kasmi, Y Kato, W Ketchum, J Keung, B Kilminster, DH Kim, HS Kim, JE Kim, MJ Kim, SB Kim, SH Kim, YK Kim, YJ Kim, N Kimura, M Kirby, K Knoepfel, K Kondo, DJ Kong, J Konigsberg, AV Kotwal, M Kreps, J Kroll, M Kruse, T Kuhr, M Kurata, AT Laasanen, S Lammel, M Lancaster, K Lannon, G Latino, HS Lee, JS Lee, S Leo, S Leone, JD Lewis, A Limosani, E Lipeles, A Lister, H Liu, Q Liu, T Liu, S Lockwitz, A Loginov, A Lucà, D Lucchesi, J Lueck, P Lujan, P Lukens, G Lungu, J Lys, R Lysak, R Madrak, P Maestro, S Malik, G Manca, A Manousakis-Katsikakis, F Margaroli, P Marino, M Martínez, K Matera, ME Mattson, A Mazzacane, P Mazzanti, R McNulty, A Mehta, P Mehtala, C Mesropian, T Miao, D Mietlicki, A Mitra, H Miyake, S Moed, N Moggi, CS Moon, R Moore, MJ Morello, A Mukherjee, Th Muller, P Murat, M Mussini, J Nachtman, Y Nagai, J Naganoma, I Nakano, A Napier, J Nett, C Neu, T Nigmanov, L Nodulman, SY Noh, O Norniella, L Oakes, SH Oh, YD Oh, I Oksuzian, T Okusawa, R Orava, L Ortolan, C Pagliarone, E Palencia, P Palni, V Papadimitriou, W Parker, G Pauletta, M Paulini, C Paus, TJ Phillips, G Piacentino, E Pianori, J Pilot, K Pitts, C Plager, L Pondrom, S Poprocki, K Potamianos, F Prokoshin, A Pranko, F Ptohos, G Punzi, N Ranjan, I Redondo Fernández, P Renton, M Rescigno, F Rimondi, L Ristori, A Robson, T Rodriguez, S Rolli, M Ronzani, R Roser, JL Rosner, F Ruffini, A Ruiz, J Russ, V Rusu, WK Sakumoto, Y Sakurai, L Santi, K Sato, V Saveliev, A Savoy-Navarro, P Schlabach, EE Schmidt, T Schwarz, L Scodellaro, F Scuri, S Seidel, Y Seiya, A Semenov, F Sforza, SZ Shalhout, T Shears, PF Shepard, M Shimojima, M Shochet, I Shreyber-Tecker, A Simonenko, K Sliwa, JR Smith, FD Snider, V Sorin, H Song, M Stancari, R St Denis, D Stentz, J Strologas, Y Sudo, A Sukhanov, I Suslov, K Takemasa, Y Takeuchi, J Tang, M Tecchio, PK Teng, J Thom, E Thomson, V Thukral, D Toback, S Tokar, K Tollefson, T Tomura, D Tonelli, S Torre, D Torretta, P Totaro, M Trovato, F Ukegawa, S Uozumi, F Vázquez, G Velev, C Vellidis, C Vernieri, M Vidal, R Vilar, J Vizán, M Vogel, G Volpi, P Wagner, R Wallny, SM Wang, D Waters, WC Wester III, D Whiteson, AB Wicklund, S Wilbur, HH Williams, JS Wilson, P Wilson, BL Winer, P Wittich, S Wolbers, H Wolfe, T Wright, X Wu, Z Wu, K Yamamoto, D Yamato, T Yang, UK Yang, YC Yang, W-M Yao, GP Yeh, K Yi, J Yoh, K Yorita, T Yoshida, GB Yu, I Yu, AM Zanetti, Y Zeng, C Zhou, S Zucchelli

Abstract:

Using data from proton-antiproton collisions at Ecms=1.96 TeV recorded by the CDF II detector at the Fermilab Tevatron, evidence for the excited resonance state Lambda_b* is presented in its Lambda_b0 pi+ pi- decay, followed by the Lambda_b0 -->Lambda_c+ (-->proton K- pi+) pi- decays. The analysis is based on a data sample corresponding to an integrated luminosity of 9.6/fb collected by an online event selection based on charged-particle tracks displaced from the proton-antiproton interaction point. The significance of the observed signal is 3.5 Gaussian sigmas. The mass of the observed state is found to be 5919.22 +- 0.76 MeV in agreement with similar findings in proton-proton collision experiments.

Measurement of the leptonic asymmetry in ttbar events produced in ppbar collisions at sqrt(s)=1.96 TeV

(2013)

Authors:

CDF Collaboration, T Aaltonen, S Amerio, D Amidei, A Anastassov, A Annovi, J Antos, G Apollinari, JA Appel, T Arisawa, A Artikov, J Asaadi, W Ashmanskas, B Auerbach, A Aurisano, F Azfar, W Badgett, T Bae, A Barbaro-Galtieri, VE Barnes, BA Barnett, P Barria, P Bartos, M Bauce, F Bedeschi, S Behari, G Bellettini, J Bellinger, D Benjamin, A Beretvas, A Bhatti, KR Bland, B Blumenfeld, A Bocci, A Bodek, D Bortoletto, J Boudreau, A Boveia, L Brigliadori, C Bromberg, E Brucken, J Budagov, HS Budd, K Burkett, G Busetto, P Bussey, P Butti, A Buzatu, A Calamba, S Camarda, M Campanelli, F Canelli, B Carls, D Carlsmith, R Carosi, S Carrillo, B Casal, M Casarsa, A Castro, P Catastini, D Cauz, V Cavaliere, M Cavalli-Sforza, A Cerri, L Cerrito, YC Chen, M Chertok, G Chiarelli, G Chlachidze, K Cho, D Chokheli, A Clark, C Clarke, ME Convery, J Conway, M Corbo, M Cordelli, CA Cox, DJ Cox, M Cremonesi, D Cruz, J Cuevas, R Culbertson, N d'Ascenzo, M Datta, P de Barbaro, L Demortier, L Marchese, M Deninno, F Devoto, M D'Errico, A Di Canto, B Di Ruzza, JR Dittmann, M D'Onofrio, S Donati, M Dorigo, A Driutti, K Ebina, R Edgar, A Elagin, R Erbacher, S Errede, B Esham, S Farrington, JP Fernández Ramos, R Field, G Flanagan, R Forrest, M Franklin, JC Freeman, H Frisch, Y Funakoshi, C Galloni, AF Garfinkel, P Garosi, H Gerberich, E Gerchtein, S Giagu, V Giakoumopoulou, K Gibson, CM Ginsburg, N Giokaris, P Giromini, G Giurgiu, V Glagolev, D Glenzinski, M Gold, D Goldin, A Golossanov, G Gomez, G Gomez-Ceballos, M Goncharov, O González López, I Gorelov, AT Goshaw, K Goulianos, E Gramellini, S Grinstein, C Grosso-Pilcher, RC Group, J Guimaraes da Costa, SR Hahn, JY Han, F Happacher, K Hara, M Hare, RF Harr, T Harrington-Taber, K Hatakeyama, C Hays, J Heinrich, M Herndon, A Hocker, Z Hong, W Hopkins, S Hou, RE Hughes, U Husemann, M Hussein, J Huston, G Introzzi, M Iori, A Ivanov, E James, D Jang, B Jayatilaka, EJ Jeon, S Jindariani, M Jones, KK Joo, SY Jun, TR Junk, M Kambeitz, T Kamon, PE Karchin, A Kasmi, Y Kato, W Ketchum, J Keung, B Kilminster, DH Kim, HS Kim, JE Kim, MJ Kim, SB Kim, SH Kim, YK Kim, YJ Kim, N Kimura, M Kirby, K Knoepfel, K Kondo, DJ Kong, J Konigsberg, AV Kotwal, M Kreps, J Kroll, M Kruse, T Kuhr, M Kurata, AT Laasanen, S Lammel, M Lancaster, K Lannon, G Latino, HS Lee, JS Lee, S Leo, S Leone, JD Lewis, A Limosani, E Lipeles, A Lister, H Liu, Q Liu, T Liu, S Lockwitz, A Loginov, A Lucà, D Lucchesi, J Lueck, P Lujan, P Lukens, G Lungu, J Lys, R Lysak, R Madrak, P Maestro, S Malik, G Manca, A Manousakis-Katsikakis, F Margaroli, P Marino, M Martínez, K Matera, ME Mattson, A Mazzacane, P Mazzanti, R McNulty, A Mehta, P Mehtala, C Mesropian, T Miao, D Mietlicki, A Mitra, H Miyake, S Moed, N Moggi, CS Moon, R Moore, MJ Morello, A Mukherjee, Th Muller, P Murat, M Mussini, J Nachtman, Y Nagai, J Naganoma, I Nakano, A Napier, J Nett, C Neu, T Nigmanov, L Nodulman, SY Noh, O Norniella, L Oakes, SH Oh, YD Oh, I Oksuzian, T Okusawa, R Orava, L Ortolan, C Pagliarone, E Palencia, P Palni, V Papadimitriou, W Parker, G Pauletta, M Paulini, C Paus, TJ Phillips, G Piacentino, E Pianori, J Pilot, K Pitts, C Plager, L Pondrom, S Poprocki, K Potamianos, F Prokoshin, A Pranko, F Ptohos, G Punzi, N Ranjan, I Redondo Fernández, P Renton, M Rescigno, F Rimondi, L Ristori, A Robson, T Rodriguez, S Rolli, M Ronzani, R Roser, JL Rosner, F Ruffini, A Ruiz, J Russ, V Rusu, WK Sakumoto, Y Sakurai, L Santi, K Sato, V Saveliev, A Savoy-Navarro, P Schlabach, EE Schmidt, T Schwarz, L Scodellaro, F Scuri, S Seidel, Y Seiya, A Semenov, F Sforza, SZ Shalhout, T Shears, PF Shepard, M Shimojima, M Shochet, I Shreyber-Tecker, A Simonenko, K Sliwa, JR Smith, FD Snider, V Sorin, H Song, M Stancari, R St Denis, D Stentz, J Strologas, Y Sudo, A Sukhanov, I Suslov, K Takemasa, Y Takeuchi, J Tang, M Tecchio, PK Teng, J Thom, E Thomson, V Thukral, D Toback, S Tokar, K Tollefson, T Tomura, D Tonelli, S Torre, D Torretta, P Totaro, M Trovato, F Ukegawa, S Uozumi, F Vázquez, G Velev, C Vellidis, C Vernieri, M Vidal, R Vilar, J Vizán, M Vogel, G Volpi, P Wagner, R Wallny, SM Wang, D Waters, WC Wester, D Whiteson, AB Wicklund, S Wilbur, HH Williams, JS Wilson, P Wilson, BL Winer, P Wittich, S Wolbers, H Wolfe, T Wright, X Wu, Z Wu, K Yamamoto, D Yamato, T Yang, UK Yang, YC Yang, W-M Yao, GP Yeh, K Yi, J Yoh, K Yorita, T Yoshida, GB Yu, I Yu, AM Zanetti, Y Zeng, C Zhou, S Zucchelli

Measurement of the leptonic asymmetry in ttbar events produced in ppbar collisions at sqrt(s)=1.96 TeV

ArXiv 1308.112 (2013)

Authors:

CDF Collaboration, T Aaltonen, S Amerio, D Amidei, A Anastassov, A Annovi, J Antos, G Apollinari, JA Appel, T Arisawa, A Artikov, J Asaadi, W Ashmanskas, B Auerbach, A Aurisano, F Azfar, W Badgett, T Bae, A Barbaro-Galtieri, VE Barnes, BA Barnett, P Barria, P Bartos, M Bauce, F Bedeschi, S Behari, G Bellettini, J Bellinger, D Benjamin, A Beretvas, A Bhatti, KR Bland, B Blumenfeld, A Bocci, A Bodek, D Bortoletto, J Boudreau, A Boveia, L Brigliadori, C Bromberg, E Brucken, J Budagov, HS Budd, K Burkett, G Busetto, P Bussey, P Butti, A Buzatu, A Calamba, S Camarda, M Campanelli, F Canelli, B Carls, D Carlsmith, R Carosi, S Carrillo, B Casal, M Casarsa, A Castro, P Catastini, D Cauz, V Cavaliere, M Cavalli-Sforza, A Cerri, L Cerrito, YC Chen, M Chertok, G Chiarelli, G Chlachidze, K Cho, D Chokheli, A Clark, C Clarke, ME Convery, J Conway, M Corbo, M Cordelli, CA Cox, DJ Cox, M Cremonesi, D Cruz, J Cuevas, R Culbertson, N d'Ascenzo, M Datta, P de Barbaro, L Demortier, L Marchese, M Deninno, F Devoto, M D'Errico, A Di Canto, B Di Ruzza, JR Dittmann, M D'Onofrio, S Donati, M Dorigo, A Driutti, K Ebina, R Edgar, A Elagin, R Erbacher, S Errede, B Esham, S Farrington, JP Fernández Ramos, R Field, G Flanagan, R Forrest, M Franklin, JC Freeman, H Frisch, Y Funakoshi, C Galloni, AF Garfinkel, P Garosi, H Gerberich, E Gerchtein, S Giagu, V Giakoumopoulou, K Gibson, CM Ginsburg, N Giokaris, P Giromini, G Giurgiu, V Glagolev, D Glenzinski, M Gold, D Goldin, A Golossanov, G Gomez, G Gomez-Ceballos, M Goncharov, O González López, I Gorelov, AT Goshaw, K Goulianos, E Gramellini, S Grinstein, C Grosso-Pilcher, RC Group, J Guimaraes da Costa, SR Hahn, JY Han, F Happacher, K Hara, M Hare, RF Harr, T Harrington-Taber, K Hatakeyama, C Hays, J Heinrich, M Herndon, A Hocker, Z Hong, W Hopkins, S Hou, RE Hughes, U Husemann, M Hussein, J Huston, G Introzzi, M Iori, A Ivanov, E James, D Jang, B Jayatilaka, EJ Jeon, S Jindariani, M Jones, KK Joo, SY Jun, TR Junk, M Kambeitz, T Kamon, PE Karchin, A Kasmi, Y Kato, W Ketchum, J Keung, B Kilminster, DH Kim, HS Kim, JE Kim, MJ Kim, SB Kim, SH Kim, YK Kim, YJ Kim, N Kimura, M Kirby, K Knoepfel, K Kondo, DJ Kong, J Konigsberg, AV Kotwal, M Kreps, J Kroll, M Kruse, T Kuhr, M Kurata, AT Laasanen, S Lammel, M Lancaster, K Lannon, G Latino, HS Lee, JS Lee, S Leo, S Leone, JD Lewis, A Limosani, E Lipeles, A Lister, H Liu, Q Liu, T Liu, S Lockwitz, A Loginov, A Lucà, D Lucchesi, J Lueck, P Lujan, P Lukens, G Lungu, J Lys, R Lysak, R Madrak, P Maestro, S Malik, G Manca, A Manousakis-Katsikakis, F Margaroli, P Marino, M Martínez, K Matera, ME Mattson, A Mazzacane, P Mazzanti, R McNulty, A Mehta, P Mehtala, C Mesropian, T Miao, D Mietlicki, A Mitra, H Miyake, S Moed, N Moggi, CS Moon, R Moore, MJ Morello, A Mukherjee, Th Muller, P Murat, M Mussini, J Nachtman, Y Nagai, J Naganoma, I Nakano, A Napier, J Nett, C Neu, T Nigmanov, L Nodulman, SY Noh, O Norniella, L Oakes, SH Oh, YD Oh, I Oksuzian, T Okusawa, R Orava, L Ortolan, C Pagliarone, E Palencia, P Palni, V Papadimitriou, W Parker, G Pauletta, M Paulini, C Paus, TJ Phillips, G Piacentino, E Pianori, J Pilot, K Pitts, C Plager, L Pondrom, S Poprocki, K Potamianos, F Prokoshin, A Pranko, F Ptohos, G Punzi, N Ranjan, I Redondo Fernández, P Renton, M Rescigno, F Rimondi, L Ristori, A Robson, T Rodriguez, S Rolli, M Ronzani, R Roser, JL Rosner, F Ruffini, A Ruiz, J Russ, V Rusu, WK Sakumoto, Y Sakurai, L Santi, K Sato, V Saveliev, A Savoy-Navarro, P Schlabach, EE Schmidt, T Schwarz, L Scodellaro, F Scuri, S Seidel, Y Seiya, A Semenov, F Sforza, SZ Shalhout, T Shears, PF Shepard, M Shimojima, M Shochet, I Shreyber-Tecker, A Simonenko, K Sliwa, JR Smith, FD Snider, V Sorin, H Song, M Stancari, R St Denis, D Stentz, J Strologas, Y Sudo, A Sukhanov, I Suslov, K Takemasa, Y Takeuchi, J Tang, M Tecchio, PK Teng, J Thom, E Thomson, V Thukral, D Toback, S Tokar, K Tollefson, T Tomura, D Tonelli, S Torre, D Torretta, P Totaro, M Trovato, F Ukegawa, S Uozumi, F Vázquez, G Velev, C Vellidis, C Vernieri, M Vidal, R Vilar, J Vizán, M Vogel, G Volpi, P Wagner, R Wallny, SM Wang, D Waters, WC Wester III, D Whiteson, AB Wicklund, S Wilbur, HH Williams, JS Wilson, P Wilson, BL Winer, P Wittich, S Wolbers, H Wolfe, T Wright, X Wu, Z Wu, K Yamamoto, D Yamato, T Yang, UK Yang, YC Yang, W-M Yao, GP Yeh, K Yi, J Yoh, K Yorita, T Yoshida, GB Yu, I Yu, AM Zanetti, Y Zeng, C Zhou, S Zucchelli

Abstract:

We measure the asymmetry in the charge-weighted rapidity of the lepton in semileptonic ttbar decays recorded with the CDF II detector using the full Tevatron Run II sample, corresponding to an integrated luminosity of 9.4/fb. A parametrization of the asymmetry as a function of the charge-weighted rapidity is used to correct for the finite acceptance of the detector and recover the production-level asymmetry. The result of afb(lep) = 0.094 +0.032 -0.029 is to be compared to the standard model next-to-leading-order prediction of afb(lep) = 0.038 +-0.003.

Measurement of the inclusive jet cross-section in pp collisions at √s = 2.76 TeV and comparison to the inclusive jet cross-section at √s = 7 TeV using the ATLAS detector

European Physical Journal C 73:8 (2013)

Authors:

G Aad, T Abajyan, B Abbott, J Abdallah, SA Khalek, AA Abdelalim, O Abdinov, R Aben, B Abi, M Abolins, OSA Zeid, H Abramowicz, H Abreu, BS Acharya, L Adamczyk, DL Adams, TN Addy, J Adelman, S Adomeit, P Adragna, T Adye, S Aefsky, JA Aguilar-Saavedra, M Agustoni, M Aharrouche, SP Ahlen, F Ahles, A Ahmad, M Ahsan, G Aielli, TPA Åkesson, G Akimoto, AV Akimov, MS Alam, MA Alam, J Albert, S Albrand, M Aleksa, IN Aleksandrov, F Alessandria, C Alexa, G Alexander, G Alexandre, T Alexopoulos, M Alhroob, M Aliev, G Alimonti, J Alison, BMM Allbrooke, PP Allport, SE Allwood-Spiers, J Almond, A Aloisio, R Alon, A Alonso, F Alonso, A Altheimer, BA Gonzalez, MG Alviggi, K Amako, C Amelung, VV Ammosov, SPA Dos Santos, A Amorim, N Amram, C Anastopoulos, LS Ancu, N Andari, T Andeen, CF Anders, G Anders, KJ Anderson, A Andreazza, V Andrei, ML Andrieux, 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, S Aoun, LA Bella, R Apolle, G Arabidze, I Aracena, Y Arai, ATH Arce, S Arfaoui, JF Arguin, S Argyropoulos, E Arik

Abstract:

The inclusive jet cross-section has been measured in proton–proton collisions at √s = 2.76 TeV in a dataset corresponding to an integrated luminosity of 0.20 pb−1 collected with the ATLAS detector at the Large Hadron Collider in 2011. Jets are identified using the anti-kt algorithm with two radius parameters of 0.4 and 0.6. The inclusive jet double-differential cross-section is presented as a function of the jet transverse momentum pT and jet rapidity y, covering a range of 20 ≤ pT < 430 GeV and |y| < 4.4. The ratio of the cross-section to the inclusive jet cross-section measurement at √s = 7 TeV, published by the ATLAS Collaboration, is calculated as a function of both transverse momentum and the dimensionless quantity xT = 2pT/ √s, in bins of jet rapidity. The systematic uncertainties on the ratios are significantly reduced due to the cancellation of correlated uncertainties in the two measurements. Results are compared to the prediction from next-to-leading order perturbative QCD calculations corrected for non-perturbative effects, and next-to-leading order Monte Carlo simulation. Furthermore, the ATLAS jet cross-section measurements at √s = 2.76 TeV and √s = 7 TeV are analysed within a framework of next-to-leading order perturbative QCD calculations to determine parton distribution functions of the proton, taking into account the correlations between the measurements.

Herschel-atlas: A binary HyLIRG pinpointing a cluster of starbursting protoellipticals

Astrophysical Journal 772:2 (2013)

Authors:

RJ Ivison, AM Swinbank, I Smail, AI Harris, RS Bussmann, A Cooray, P Cox, H Fu, A Kovács, M Krips, D Narayanan, M Negrello, R Neri, J Peñarrubia, J Richard, DA Riechers, K Rowlands, JG Staguhn, TA Targett, S Amber, AJ Baker, N Bourne, F Bertoldi, M Bremer, JA Calanog, DL Clements, H Dannerbauer, A Dariush, G De Zotti, L Dunne, SA Eales, D Farrah, S Fleuren, A Franceschini, JE Geach, RD George, JC Helly, R Hopwood, E Ibar, MJ Jarvis, JP Kneib, S Maddox, A Omont, D Scott, S Serjeant, MWL Smith, MA Thompson, E Valiante, I Valtchanov, J Vieira, P Van Der Werf

Abstract:

Panchromatic observations of the best candidate hyperluminous infrared galaxies from the widest Herschel extragalactic imaging survey have led to the discovery of at least four intrinsically luminous z = 2.41 galaxies across an ≈100 kpc region - a cluster of starbursting protoellipticals. Via subarcsecond interferometric imaging we have measured accurate gas and star formation surface densities. The two brightest galaxies span ∼3 kpc FWHM in submillimeter/radio continuum and CO J = 4-3, and double that in CO J = 1-0. The broad CO line is due partly to the multitude of constituent galaxies and partly to large rotational velocities in two counter-rotating gas disks - a scenario predicted to lead to the most intense starbursts, which will therefore come in pairs. The disks have M dyn of several × 1011 M o, and gas fractions of ∼40%. Velocity dispersions are modest so the disks are unstable, potentially on scales commensurate with their radii: these galaxies are undergoing extreme bursts of star formation, not confined to their nuclei, at close to the Eddington limit. Their specific star formation rates place them ≳ 5 × above the main sequence, which supposedly comprises large gas disks like these. Their high star formation efficiencies are difficult to reconcile with a simple volumetric star formation law. N-body and dark matter simulations suggest that this system is the progenitor of a B(inary)-type ≈1014.6- o cluster. © 2013. The American Astronomical Society. All rights reserved.