Lightest Nuclei in UHECR versus Tau Neutrino Astronomy

📝 Abstract

UHECR may be either nucleons or nuclei; in the latter case the Lightest Nuclei, as He, Li, Be, explains at best the absence of Virgo signals and the crowding of events around Cen-A bent by galactic magnetic fields. This model fit the observed nuclear mass composition discovered in AUGER. However UHECR nucleons above GZK produce EeV neutrinos while Heavy Nuclei, as Fe UHECR do not produce much. UHECR He nuclei at few tens EeV suffer nuclear fragmentation (producing low energetic neutrino at tens PeVs) but it suffer anyway photo-pion GZK suppression (leading to EeV neutrinos) once above one-few 10^{20} eV. Both these cosmogenic UHE secondary neutrinos signals may influence usual predicted GZK Tau Neutrino Astronomy in significant and detectable way; the role of resonant antineutrino electron-electron leading to Tau air-shower may also rise.

💡 Analysis

UHECR may be either nucleons or nuclei; in the latter case the Lightest Nuclei, as He, Li, Be, explains at best the absence of Virgo signals and the crowding of events around Cen-A bent by galactic magnetic fields. This model fit the observed nuclear mass composition discovered in AUGER. However UHECR nucleons above GZK produce EeV neutrinos while Heavy Nuclei, as Fe UHECR do not produce much. UHECR He nuclei at few tens EeV suffer nuclear fragmentation (producing low energetic neutrino at tens PeVs) but it suffer anyway photo-pion GZK suppression (leading to EeV neutrinos) once above one-few 10^{20} eV. Both these cosmogenic UHE secondary neutrinos signals may influence usual predicted GZK Tau Neutrino Astronomy in significant and detectable way; the role of resonant antineutrino electron-electron leading to Tau air-shower may also rise.

📄 Content

arXiv:0902.3290v1 [astro-ph.HE] 19 Feb 2009 Lightest Nuclei in UHECR versus Tau Neutrino Astronomy D.Fargiona, D. D’Armiento, P. Paggi, S. Patri’ aPhysics Department and INFN, Rome University 1, Sapienza, Ple.A.Moro 2 UHECR may be either nucleons [2] or nuclei; in the latter case the Lightest Nuclei, as He4 or He3, Li, Be , explains at best the absence of Virgo signals and the crowding of events around Cen-A bent by galactic magnetic fields [3]. This model fit the observed nuclear mass composition discovered in AUGER. However UHECR nucleons above GZK produce EeV neutrinos while Heavy Nuclei, as Fe UHECR do not produce much. UHECR He nuclei at few 1019eV suffer nuclear fragmentation (producing low energetic neutrino at tens PeVs) but it suffer anyway photo-pion GZK suppression (leading to EeV neutrinos) once above one-few 1020eV . Both these cosmogenic UHE secondary neutrinos signals may influence usual predicted GZK [9],[12] Tau Neutrino Astronomy [4] in significant and detectable way; the role of resonant antineutrino electron-electron leading to Tau air-shower may also rise. 1. UHECR Lightest Nuclei versus UHE ν Astrophysical UHE neutrinos is being searched, since four decades, at TeV-PeV energy via neu- trino muons in underground detectors. Their sig- nal is greatly polluted from above (and below) by CR secondary muons (and atmospheric muon neutrinos into muons) and partially suppressed at PeVs, by Earth size opacity. Horizontal Muons at hundreds TeV, originated by astrophysical UHE neutrinos are also polluted by leading prompt at- mospheric signals. However, since four decades, the rise of highest energy neutrino Astronomy is generally expected also by the cosmogenic EeV neutrinos, secondaries of GZK [9],[12] cut-offon Ultra High Cosmic Rays (UHECR). These ones are difficult to observe in km3 detector. But since a decade [4] the UHE Tau Neutrino Astron- omy have been foreseen and suggested in present and future detectors. Indeed Tau Air-shower As- tronomy is an amplified Neutrino Astronomy ob- servable. Indeed an air-shower is not a single track, but a wide (even many km2) area rain- ing of billions secondaries at once. One doesn’t need to collect and count all of them to real- ize such an event beyond a mountain or Earth screen. One need just a spread sample at once. As for UHECR. Moreover hadronic air-shower be- low zenith angle 75o are originated far and far and they are filtered : their peak electromagnetic component is exhausted at horizons leaving just late diluted (and sharp) inclined muon bundles. On the contrary neutrino, either interacting in air or, better, escaping the Earth by ντ →τ may lead to electromagnetic-rich horizontal (upward) air-showers. Tau decay in flight are better than neutrino interacting in air because Earth rock density is three thousand times larger than air one. Even if the tau enjoy of a bounded escaping solid angle (a zenith angle width of 2 −5o de- gree) while all down-ward neutrinos interacting on air may reach from wider cone (a zenith angle width 15o degree) and are in three flavors. Such skimming events in AUGER experiment may rise via upward tau air-shower [4],[6],[7]. In last years the upward-horizontal EeV τ,¯τ appearance, via UHECR p + γCMB →π →ν has been pre- dicted by many authors; the most extreme ones were at rate of 0.1 −0.03 a year[7], or 0.3 a year in AUGER [5] and finally up to 0.2 a year [8]. This rate, has only recently being adjusted and confirmed by last AUGER group estimates (NOW 2008, CRIS 2008):0.3 a year, in full agree- ment with our previous ones [5]. Indeed follow- ing the AUGER evidences (and Hires ones [10]) of an UHECR GZK[9],[12] cut-offand the lat- est AUGER (possible) Super-Galactic anisotropy due to an eventual proton UHECR guarantee a secondary flux of UHE-GZK neutrino at EeVs energy within AUGER detection via τ,¯τ show- 1 2 ering [5]. In fact this occurs because the muon neutrino flavor mixing must feed also a tau neu- trino component. Such UHE astrophysical tau neutrino (noise-free from any atmospheric back- ground) may interact in and it may rises out the Earth as UHE τ. The UHE τ,¯τ decay in flight in atmosphere must lead to loud Tau Air- showers. Such a detectable flashes may rise in short times within Auger SD (by large electro- magnetic curvature signals) or in FD arrays by horizontal fluorescence signals, namely once in a few years (2 −4) from now [5]. Nevertheless a re- cent alternative UHECR understanding [3], based on observed AUGER UHECR (nuclei) mass com- position and with Cen-A rich clustering map, is in disagreement with UHECR proton understand- ing [2]. This model is leading to different UHE neutrino predictions. It suggests that UHECR are made by Lightest Nuclei (He4, He3, maybe a few also Be,Li) mostly originated from Cen-A: their trajectories are bent and spread by galac- tic magnetic fields and they are incidentally clus- tered ( by galactic fields) around Cen-A, near- est (4 Mpc) and possibly unique source able to survive the short Ligh

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