Cosmological Constraints on high energy neutrino injection. KEKPH07 March 1-3, 2007

Transcription

1 Cosmological Constraints on high energy neutrino injection KEKPH07 March 1-3, 2007 Toru Kanzaki, Masahiro Kawasaki, Kazunori Kohri and Takeo Moroi Institute for Cosmic Ray Research

2 Introduction physics beyond the Standard model To solve { hierarchy problem dark matter. Supersymmetry (SUSY) is a prominent candidate. the existence of exotic long-lived particle X, e.g. gravitino ( In the framework of string theories, moduli ) We derive general and model-independent constraints on the relic abundance of X.

3 The decay of X have significant effects on cosmology, especially, the Big-Bang Nucleosynthesis (BBN) the Cosmic Microwave Background (CMB) diffuse photon flux diffuse neutrino flux decay product ( sec) ( sec) (10 12 sec ) What observation gives the most stringent constraints depends on the lifetime and decay products of X. X Y + γ an invisible particle X Y + ν { X Y + ν + Z(Z ) X Y + l + W (W ) main decay mode 3,4-body decay mode ( Branching ratio B X ) 3 free parameters: m X, τ X, B X B X Γ(X 3, 4body)/Γ(X all)

4 BBN constraints : ( Reno and Seckel 1988 ) ( Dimopoulos et.al ) ( Kawasaki and Moroi 1995 ) ( Kawasaki, Kohri and Moroi 2005 ) If the decay of X occur during or after BBN, the standard particles emitted in the decay can affect the abundance of primordial light elements. Resultant abundances of light elements may significantly conflict with observations. As a result, the relic abundance of X is severely constrained. ν + ν BG 2-body decay : X Y + ν { l+ + l π + + π electromagnetic shower p-n conversion 3,4-body decay : X Y + ν + Z(Z ), Y + l + W (W ) l, W, Z electromagnetic shower W, Z hadronic shower

5 B X = 10 3 m X = 300GeV lifetime Here we define yield value : Y X [ nx s 4 p-n conversion : He overproduction ] t τ X lifetime short 6 hadronic shower : D and Li overproduction 3 electromagnetic shower : He overproduction long

6 CMB constraints : y and µ distortions ( Silk and Stebbins 1983 ) ( Kawasaki and Sato 1986 ) ( Hu and Silk 1993 ) COBE observations show that the CMB spectrum is almost perfect blackbody. Therefore, any photon energy injection that cause distortions in the spectum of CMB are severely constrained. { µ ρ γ ρ γ µ distortion : (10 5 z 10 7 ) y distortion : y body decay ρ γ ρ γ (10 3 z 10 5 ) ν + ν BG l + + l exotic photon energy 3,4-body decay X Y + ν + Z(Z ), Y + l + W (W ) µ y ( COBE 1996, Smoot and Scott 1997 ) Some of the energy of these particles convert to photon energy.

7 B X = 10 6 m X = 10 2 GeV B X = 10 3 m X = 10 2 GeV lifetime lifetime When lifetime is short, the constraints are determined by 2-body decay. The constraints become severe with larger m X When lifetime is long, the constraints are determined by 3,4-body decay. The constraints become severe with smaller m X E X γ /E X = (m X = 100GeV) E X γ /E X = (m X = 10 5 GeV)

8 diffuse neutrino constraints : ( Ellis et. al ) ( Gondolo, Gelmini and Sarkar 1993 ) ( Beacom, Bell and Mack 2006 ) 2-body decay : X Y + ν (E ν = m X /2) When neutrino injection takes place at late time, the emitted neutrinos may produce an observable peak in the diffuse neutrino ν µ + ν µ spectrum. The atmospheric neutrino { Super-Kamiokande AMANDA (ν µ + ν µ ) has been observed by ( GeV) ( GeV) ( Ashie et. al ) ( Gonzalez-Garcia et. al ) ( Geenen et. al ) To obtain the constraints on the neutrino flux, we require that the signal from injected neutrino should not exceed the atmospheric neutrino.

9 No appreciable signal of ν e was detected at SK. through ( ν e + p n + e + ) This experiment set the upper bound of above a threshold energy. ν e background flux The upper bound of the diffuse signal ν e is given by Super-Kamiokande Φ ν < 1.2cm 2 s 1 for E ν > 19.3MeV ( Malek et. al )

10 SK m X = 10 3 GeV m X = 10 5 GeV τ X = sec AMANDA m X = 10 2 GeV present neutrino energy lifetime When lifetime is short, the constraints are determined by diffuse ν e. The constraints are in proportion to m X When lifetime is long, the constraints are determined by atmospheric neutrino. The constraints are roughly in inverse proportion to m X

11 diffuse photon constraints : There are two points different from atmospheric neutrino case : Injected photon spectrum is not monoenergetic. { photons from 3,4-body decay of X X γ photons produced by inverse Compton process and e + γ BG e + γ High energy photons scatter through various processes. { γ + γ CMB γ + γ, e + + e γ + γ IBL e + + e The diffuse photon flux has been observed by { COMPTEL EGRET (0.8 30MeV) X e (0 < z < 5) (30MeV 100GeV) ( Zdziarski and Svensson 1989 ) ( Kribs and Rothstein 1997 ) ( Salamon and Stecker 1998 ) ( Primack et. al ) ( Stecker, Malkan and Scully 2006 ) ( Kappadath et. al ) ( Sreekumarand et. al )

12 τ X = sec COMPTEL m X = 10 3 GeV m X = 10 5 GeV EGRET m X = 10 2 GeV present photon energy lifetime The constraints are almost independent of m X at early time. High energy photons are effectively absorbed by IBL photons.

13 Results : B X = 10 3 m X = 300GeV lifetime m X B X BBN CMB early time late time diffuse neutrino diffuse photon severe severe loose severe loose severe irrelevant severe irrelevant severe

14 Conclusions : We have considered the long-lived particle X which mainly decay into neutrino and investigated the effect of decay of X on cosmology. We derive general and model-independent constraints on the abundance of X from the BBN, CMB, diffuse neutrino and diffuse photon flux. We show that the BBN and diffuse neutrino flux provide stringent constraints on the abundance of X with larger mass.

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16 Hadronic energy injection At early epoch (t < 10 2 sec) The emitted hadrons do not directly destroy the light elements due to the quick energy loss through EM interaction. The mesons with relatively long lifetimes such as can cause the p n conversion. π ± and K 0,± At later epoch (t > 10 2 sec) The high energy p and n interact with background hadrons before they lose energy, and produce secondary hadrons. Such hadronic interactions occur successively and evolve into hadronic shower ( hadro-dissociation )

17 p n conversion The Hadron-Nucleon interaction rate should be greater than the decay rate. Hadron-Nucleon interaction rate : Γ N N ( sec) 1 ( σv 40mb pion π + + n p + π 0, p + γ { π + p n + π 0, n + γ ) ( T ) 3 1MeV kaon { K + n Σ + π 0, K L + N N + Lifetime : τ π ± = sec τ K ± = sec = sec τ KL

18 Freeze-out of weak interaction (T 0.84MeV) n + ν p + e, n/p 1/6 n + e + p + ν The formation of the light elements n/p 1/7 n/p 1/7 + neutron decay + p n conversion (T 0.08MeV) ( This determines completely. ) Y p More 4 He n/p ratio increases

19 hadro-dissociation High energy p and n scatter off the background baryons before stopping. background p BG n(p) + p BG n(p) + p n(p) + p BG n(p) + p + π, background α BG n(p) + α BG n(p) + α n(p) + α BG D + T ( 3 He) n(p) + α BG n + n(p) + 3 He n(p) + α BG p + n(p) + T, D, T and 3 He are produced from the 4 He dissociation.

20 non-thermal production of 6 Li is not thought to be of primordial origin due to the cross section D(α, γ) 6 Li being small. 6 Li ( Nollett, Lemoine, Schramm 1997 ) non-thermal production of T and n(p) + α BG D + T ( 3 He) n(p) + α BG n + n(p) + 3 He n(p) + α BG p + n(p) + T, 3 He non-thermal production of 6 Li T + 4 He 6 Li + n [4.03MeV] 3 He + 4 He 6 Li + p [4.8MeV]

21 Electromagnetic energy injection electromagnetic cascade processes Photon-photon pair creation γ + γ BG e + + e (ɛ γ m e 2 /22T ) Photon-photon scattering γ + γ BG γ + γ (ɛ γ m e 2 /80T ) Inverse Compton e + γ BG e + γ Compton scattering γ + e BG γ + e

22 High-energy photon is quickly thermalized by photon-photon process. ɛ γ 2.2MeV ɛ γ 20MeV (T < 10keV or t > 10 4 sec) (T < 1keV or t > 10 6 sec) The destruction of light elements takes place only if binding energy is under this threshold energy. t > 10 4 sec : D overdestruction D + γ n + p [2.22MeV] T + γ D + n [6.2MeV] 3 He + γ D + p [5.5MeV] 4 He + γ T + p [19.8MeV] t > 10 6 sec : D overproduction 4 He + γ 3 He + n [20.5MeV] 4 He + γ D + n + p [26.1MeV]

23 non-thermal production of 6 Li is not thought to be of primordial origin due to the cross section D(α, γ) 6 Li being small. 6 Li ( Nollett, Lemoine, Schramm 1997 ) non-thermal production of T and 3 He 4 He + γ T + p [19.8MeV] 4 He + γ 3 He + n [20.5MeV] non-thermal production of 6 Li T + 4 He 6 Li + n [4.03MeV] 3 He + 4 He 6 Li + p [4.8MeV]

24 m X = 10 5 GeV τ X = 10 9 sec m X = 10 2 GeV time r = E lep /(n X /τ X )/(m X /2) r is the dimensionless parameter which represents the ratio of energy transferring to photon energy per time. High energy neutrino has larger cross section for lepton pair creations. High energy neutrino is easy to exceed the threshold energy for lepton pair creations.

25 Constraints on relativistic energy A late injection of relativistic energy could be spotted in the CMB or in large scale structure (LSS) regardless of the emitted species. For decays before recombination, the effective number of neutrino species : N eff ν 4.6 (WMAP 3rd-year and SDSS LRGs) ( Ichikawa, Kawasaki and Takahashi 2006 ) B X = 10 3 B X = 10 6 m X = 10 3 GeV Constraints from N eff ν

26 m X = 10 2 GeV m X = 10 2 GeV lifetime The number of photon from decay of X is m 1 X with fixed m X Y X. { The observed neutrino flux is roughly E0 3. The observed photon flux is roughly E 2. 0 lifetime { [m X Y X ] upper bound m X m 3 X [m X Y X ] upper bound m X m 2 X m X m 1 X m X const. ( neutrino ) ( photon )