Battistoni, G

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29th International Cosmic Ray Conference Pune (2005) 6, 309312Atmospheric Neutrino Flux Calculation with FLUKA: update and firstresults on prompt contributionG. Battistoni , A. Bruno, F. Cafagna, P. Desiati, J.C. Diaz-Velez, A. Ferrari  ,T. Montaruli , P. R. Sala and A. Tamburro(a) I.N.F.N., Sezione di Milano, Via Celoria 16, 20133 Milano, Italy(b) Dipartimento di Fisica and I.N.F.N., Sezione di Bari, Via Amendola 173, 70126 Bari, Italy(c) presently on leave at CERN, CH-1211 Geneva, Switzerland(d) presently on leave at University of Wisconsin-Madison(e) University of Wisconsin-Madison, 1150 University Ave, Madison, WI 53706, USPresenter: F. Cafagna (francesco.cafagna@ba.infn.it), ita-cafagna-F-abs2-he13-posterWe show the results of the update of the atmospheric neutrino calculation based on FLUKA considering theinteraction of primary nucleons up to 10GeV/nucleon. A new primary spectrum is proposed to solve adeficit in high energy (  100 GeV) neutrinos in the calculation of 2001, and our results are compared againstother recent calculations. In addition we show for the first time our results on prompt neutrinos and muonscoming from the decay of short-lived heavy quark states. They are a serious and still highly uncertain sourceof background for neutrino telescopes, since their spectrum is harder than that of neutrinos from pion and kaondecays.1. IntroductionIn this work we present an update of the FLUKA[1] atmospheric neutrino flux calculation. Respect to thesimulation set-up used in the previous FLUKA calculation [2], a new all particle spectrum has been used,while focus has been placed in tagging secondaries resulting from the decay of short-lived charmed mesons.The semileptonic decay of heavy quark charged particles gives rise to a prompt component of the total at-mospheric neutrino flux. This component becomes more and more significant for neutrino energies above 1 TeV while the conventional component, mainly due to the pion and kaon decay chains, decreases. Thisfeature makes the neutrino flux prompt component an irreducible background for large volume neutrino tele-scopes like ANTARES, AMANDA, IceCube or NEMO [4]. Among other motivations for the study of theprompt neutrino component we cite, for example, the possibility to probe the charm production cross section athigh energy or for probing cosmic rays in a very small 	 region, not reachable at colliders [3]. For this reason itis important to fully characterize this component respect to the overall components of the cosmic ray showersin the atmosphere.The FLUKA precise simulation offers an ideal framework, not only capable to tag and isolate the promptcomponent but also to study it respect to all the other conventional components. For the first time the neutrinoprompt component has been studied in the framework of a complete and precise simulation of atmosphericshowers.2. The simulation set-upRespect to the previous FLUKA atmospheric neutrino flux calculation [2] a new all nucleon primary spectrumhas been adopted. The new spectrum has been calculated using the so called ICRC2001 one[9] up to 100 GeV.For the proton component at energies larger than 100 GeV, using the normalization obtained at 100 GeV,we assumed a spectral index of  to improve the agreement between the predicted fluxes and theMACRO and Super-Kamiokande throughgoing muon data[13]. Above the knee at 3000 TeV, we assumed aspectral index of ﬀﬁ .For what concerns the He component, above 100 GeV we used a ﬂﬃ! and a charge dependent knee310 G. Battistoni et al0 1 2 3 4 5 6 7 8410/nucleon (GeV)totalE]-1 sr-1 s-2 m1.5 dN/dE [GeV2.5 EFLUKA NewAgrawal et al.ICRC2001Figure 1. The new all nucleon primary spectrum adopted for this work compared to the ICRC2001 [9] and the Bar-tol 1996[8] ones. Spectra are reported multiplied by "$#&% ' .Figure 2. Comparison of FLUKA differential cross section (histogram) with ()( collision data (points) [11] at 400 and800 GeV/ * into +-,/.+ versus Feynman 0 and transverse momentum.has been assumed according to the rule: 13254ﬁ67698 nucleon ;:=<>ﬁ?@?ﬁ?BACD/8FE . Higher : components havebeen grouped in CNO, MgSi and Fe sets and treated using an all-particle spectrum with the above cited chargedependent knee parametrization. The resulting all-particle spectrum is reported in figure 1 and compared to theICRC2001 and previous Bartol 1996[8] fits.For the first time the possibility of tagging FLUKA secondaries produced in charmed meson decays has beenexploited making it possible to separate the contribution of the prompt component of neutrinos and muonsfrom the conventional one up to the higher energies.FLUKA is a transport and interaction code widely benchmarked against collider data and theory. For examplea comparison of the FLUKA differential cross section with GﬁG collision data at 400 and 800 GeV/ H [11] intoI8$JIversus Feynman 	 and transverse momentum is shown in figure 2. Thanks to this crosschecks a bigimprovement in the detail of the charmed production of prompt particles has been obtained[10].The simulation set-up ot the FLUKA atmospheric neutrino simulation, has been described in [2] and bench-Atmospheric Neutrino Flux Calculation with FLUKA ... 311marked on the Caprice 94 atmospheric data[12]. Primaries have been generated at an altitude of  100 km andtracked in an isothermal atmosphere reduced in a set of 100 shells of different altitude and air characteristicswhile relevant parameters for secondary muons and all neutrino flavors have been scored at sea level.3. Results and discussionAt the time of writing a total of ﬂKLB<M9?primaries has been generated in the range 0.5 N 10GeV/nucleon.Statistics are still under collection, especially at high energies, and updated results will be presented at theconference. In figure 3 we present the total flux of muon neutrinos. The spectrum is compared to the differentialenergy distributions from Bartol[5], HKKM[7] and Lipari[6] works. The ratio shown in figure 3 should beconsidered as preliminary at high energies. In that region discrepancies between calculations could be due to adifferent treatment of the knee in the primary spectra. [E (GeV)]10log1 1.5 2 2.5 3 3.5 4]-1 s-2 cm1.5 dN/dE [GeV2.5E-310-210-110BartolFLUKAHKKMLipari differential energy fluxµν+µν [E (GeV)]10log1 1.5 2 2.5 3 3.5 4Ratio0.50.60.70.80.911.11.21.31.41.5Bartol/FLUKALipari/FLUKAHKKM/FLUKAFigure 3. The total muon neutrino spectrum, scaled by " #&% ' , compared to the Bartol[5], Honda[7] and Lipari[6] ones [E (GeV)]10log1 1.5 2 2.5 3 3.5 4]-1 s-2 cm1.5 dN/dE [GeV2.5E-810-710-610-510-410-310-210-1101 conv.µν+µν conv.eν+eν promptµν+µν prompteν+eν prompt and conventional differential energy fluxeseν and µν [E (GeV)]10log1 1.5 2 2.5 3 3.5 4]-1 s-2 cm1.5 dN/dE [GeV2.5E-810-710-610-510-410-310-210-1101 conv.µν+µν conv.+µ+-µ promptµν+µν prompt+µ+-µ prompt and conventional differential energy fluxes+µ+-µ and µν+µνFigure 4. Comparison of the prompt neutrino spectra to the conventional ones for: OP and O9Q , on the left, and ORP and S , onthe right. All uxes are integrated over the full solid angle and multiplied by " #&% ' .The peculiar feature of this work is highlighted in figure 4 where conventional spectra of both muon andelectron neutrinos are compared to the prompt ones. A slightly increase of the prompt fluxes while approachingthe crossover energy is evident.Besides the prompt neutrinos, we tagged also the prompt muons. As for prompt neutrinos, prompt muons are312 G. Battistoni et altagged when created in the tracking procedure and isolated in the scoring collection routines. The correspond-ing spectra are reported in figure 4. The muon fluxes were collected from the whole solid angle. This is acomparison with the neutrino fluxes from the kinematical point of view. As a matter of fact it is noticeable theeffect of muon decay below  30 GeV and of the enhancement of the muon flux at higher energies due to thelarger energy fraction taken by the muon in the meson decays. The similarity of the prompt muon and neutrinofluxes is another feature: the neutrino one is larger (through the statistics still prevents to quote a number) inagreement with [14].In the future we plan to calculate the fluxes for neutrino energies larger than 10 T GeV, using the DPMJET-IIImodel incorporated in the FLUKA transport code.4. ConclusionsFor the first time we report on the spectra of the prompt neutrino and muon components, though with stillpreliminary statistics, of the atmospheric neutrino fluxes. These spectra has been calculated and studied usingFLUKA tagging the secondary produced in the decay chain of charmed mesons. For this calculation an updateof the FLUKA simulation set-up has been used along with a new all-particle primary spectrum.References[1] A. Fasso`, A. Ferrari, J. Ranft, and P.R. Sala, Proceedings of the MonteCarlo 2000 Conference, Lisbon,October 23–26 2000, A. Kling, F. Bara˜o, M. Nakagawa, L. Ta´vora, P. Vaz eds., Springer-Verlag Berlin,955 (2001). See also:http://www.fluka.org and references here within.[2] G. Battistoni et al., Astrop.Phys. 19, 269, (2003). Erratum-ibid.19, 291-294 (2003). e-Print Archive: hep-ph/0207035. G. Battistoni et al., High Energy Extension Of The Fluka Atmospheric Neutrino Flux, 28 UWVICRC, Tsukuba, Japan (2003), 1399-1402.[3] A.D. Martinm M.G. Ryskin and A.M. Stasto, Prompt Neutrinos From Atmospheric C Anti-C And BAnti-B Production And The Gluon At Very Small X. Published in Acta Phys.Polon. B,34, (2003), 3273-3304. e-Print Archive: hep-ph/0302140. C.G.S. Costa and C. Salles, Prompt Atmospheric Neutrinos:Phenomenology and Implications, hep-ph/01052710 (2001). J.F Beacon and F. Candia, Shower Power:Isolating the Prompt Atmospheric Neutrino Flux Using Electron Neutrinos hep-ph/0409046 (2004)[4] T. Montaruli, Neutrino Astrophysics And Telescopes, 8 UWV Workshop on Electron Nucleus Scattering, Elba,Italy (2004) and references there within. Published in: Eur.Phys.J.A, 24 S1, 103-108 (2005).[5] G.D. Barr et al., Phys. Rev. D 70, 023006 (2004), e-Print Archive: astro-ph/0403630. G.D. Barr et al.,A 3-dimensional atmospheric neutrino flux calculation , 28 UWV ICRC, Tsukuba, Japan, 1411-1414, (2003).Flux data available on: http://www-pnp.physics.ox.ac.uk/ barr/fluxfiles/0408i/index.html;[6] P. Lipari, Astropart. Phys. 1, 195-227, (1993).[7] M. Honda et al. , Phys.Rev. D, 70, 043008, (2004). Flux data available on: http://www.icrr.u-tokyo.ac.jp/ mhonda/.[8] V. Agrawal et al., Phys. Rev. D, 53, 1314, (1996).[9] T.K. Gaisser et al., Primary spectrum to 1 TeV and beyond , 27 UWV ICRC, Hamburg (2001), OG 1.01.[10] G. Battistoni et al., The Fluka Monte Carlo, Non-Perturbative Qcd And Cosmic Ray Cascades, SLAC-PUB-10981, (2004). To appear in proc. of 44 UWV Workshop on QCD at Cosmic Energies, Erice, (2004),Italy. e-Print Archive: hep-ph/0412178[11] R. Ammar et al., Phys Rev. Lett., 61,2185 (1988). M. Aguilar-Benitez et al. Z.Phys. C, 41, 181 (1988).[12] G. Battistoni et al., Astropart. Phys. 17, 477-488 (2002). e-Print Archive: hep-ph/0107241.[13] T. Montaruli, Report On The HE Phenomena Sessions He 2, He 3.2 - 3.4: Neutrinos And Muons. Interac-tions, Particle Physics Aspects, Astroparticle Physics And Cosmology. Rapporteur Papers of 28 X7Y ICRCTsukuba, Japan, 135-160 (2003). e-Print Archive: hep-ph/0311289.[14] G. Gelmini, P. Gondolo, G. Varieschi, Phys.Rev.D, 67, 017301 (2003)

Atmospheric Neutrino Flux Calculation with FLUKA: update and first results on prompt contribution

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