Searches for Neutrinos from Gamma Ray Bursts with AMANDA-II and IceCube Brennan Hughey for the IceCube Collaboration Abstract: The hadronic fireball model predicts a neutrino flux in the TeV to several PeV range simultaneous with the prompt photon emission of GRBs. The discovery of high energy neutrinos in coincidence with a gamma ray burst would help confirm the role of GRBs as accelerators of high energy cosmic rays. We summarize the methods employed by the AMANDA experiment in the search for neutrinos from GRBs and present results from several analyses. 3. Detection Channels 1. Overview 2. GRB Properties The AMANDA detector Predicted diffuse  upper bounds from GRBs for several models are shown on the right: Precursor Emission [1] Afterglow Emission [2] Prompt emission models (coincident with -ray flux): Waxman-Bahcall flux [3] Supranova model [4] Murase-Nagataki (set A flux) [5] + p →  → + → + +  → e+ + e + +  Gamma ray bursts (GRBs) are the most energetic explosions ever observed. They are predicted to produce high energy neutrinos, primarily through interactions between protons and gamma rays. Neutrinos are expected to arrive at Earth in coincidence with gamma-ray emission, although precursor and afterglow spectra have been predicted as well. The AMANDA-II detector, in operation since the year 2000, is situated in the ice deep below the South Pole station. It is composed of 677 optical modules on 19 strings. A 10-string version of the detector, called AMANDA B-10, operated from 1997-1999. Each optical module contains a photomultiplier tube which detects the Cherenkov radiation emitted by the decay products of weak force interactions between the neutrino and ice particles. (a) Muon Track (b) Cascade Event Proton-gamma interactions within relativistic jet . . . . GRB . . Artist’s conception (Image copyright NASA) . . .  . Bursts are divided into two classes based on the bimodal distribution of their durations as observed by the BATSE experiment [6]. It is thought that the different classes may arise from different progenitors. . . . . There are two primary detection channels in AMANDA, muon track events (a) and more spherically shaped particle showers, referred to as cascades (b). Muon neutrino candidates are separated from the dominant atmospheric muon background by directionality (the Earth filters out upgoing muons) while cascade events are distinguished by their unique shape. Effective areas are smaller for cascades compared to muons, but cascades can be used to search for neutrino signals from GRBs anywhere in the sky rather than just those below the horizon. . Long Bursts . . Short Bursts . Weak force interactions with nucleons in the ice . Optical Module m m- m m Z0 W+ u particle shower u particle shower AMANDA-II detector at South Pole Figure obviously not to scale 5. Rolling Search 4. Satellite-Coincident Searches Neutrino searches have been performed in coincidence with several satellites: Number Observed Number Expected 2 event windows in short burst search 311 313±18 2 event windows in long burst search 1000 1016±32 3 event windows in long burst search 20 21.6±4.8 312 bursts detected by BATSE (aboard the CGRO satellite) in the years 1997-2000 were examined using the AMANDA muon channel and 73 bursts from the year 2000 were examined using the cascade channel. BATSE ceased operations in March of 2000. 95 bursts detected by the IPN3 network were examined in addition to the BATSE bursts from the years 2000-2003. This network of gamma-ray detectors has included HETE-II, BeppoSax, Konus-Wind and Ulysses, among other satellites. The rolling search analysis was conducted using two time windows, opitmized for short and long burst classes. A total of 7 quality parameters were used to separate high energy cascade signal events from the background. Results of the analysis are consistent with no signal being observed, with the distribution of windows containing more than one event matching closely the predicted Poissonian background (see table). A rolling time window search, which looks for a clustering of events consistent with a neutrino signal from a GRB or other transient phenomenon, has been conducted using the cascade channel for the 2001, 2002 and 2003 data sets. This analysis is complementary to satellite-coincident searches, since it is designed to look for bursts with weak gamma emission or entirely photon-dark transients. Background event rates for each burst are established using off-time windows lasting an hour before and after the burst. The ten minutes surrounding the burst itself are kept blinded to allow for future analyses. No events have been observed in coincidence with any burst analyzed thus far. The Swift satellite, launched in November 2004, provides detailed information on each GRB and is being used for neutrino-coincidence searches with both AMANDA and the partially constructed IceCube array. 8. IceCube 6. Limits 7. Individually Modeled Spectra The first 9 strings of IceCube were deployed in the 2004-2005 and 2005-2006 austral summer seasons. IceCube will eventually be a cubic kilometer in size and have an effective areas nearly two orders of magnitude larger than AMANDA. Within the first few years of operation, IceCube will be able to either positively identify a GRB neutrino source or place limits constraining the current theoretical models of neutrino emission. (a) (b) Limits relative to a Waxman- Bahcall GRB flux for muon (a) and all flavor (b) analyses are shown below. All flavor limits assume e:: flavor ratios are 1:1:1. (b) Cascade all flavor limits e +  +  (a)  limits (c) references [1] S. Razzaque, P. Meszaros and E. Waxman Physical Review D, 68, 083001 2003. [2] E. Waxman and J. Bahcall, Astrophysics Journal 541, 707-711 2000. [3] E. Waxman and J. Bahcall, Phys. Rev. Lett. 80, 3690 1997. [4] S. Razzaque, P. Meszaros and E. Waxman Phys. Rev. Lett. 90, 1103 2003. [5] K. Murase and S. Nagataki, Physical Review D 73, 063 2002. [6] W.S. Paciesas et al. Astrophysics Journal, 122, 465 1999. Recent analyses are utilizing more sophisticated modeling of each GRB. By using parameters measured by Swift and other satellites, it is possible to predict unique neutrino spectra for each burst. (a): Spectra for prompt emission from individual bursts from the short burst class. (b): Predicted prompt neutrino emission for “monster burst” GRB030329 assuming isotropic emission (black) and beamed emission (blue), compared to the Waxman-Bahcall reference spectrum (red). (c): Expected events for the 3 models in AMANDA (solid) and IceCube (dashed).