Secondary production of Cosmic ray anti-helium3

Transcription

1 Secondary production of Cosmic ray anti-helium3 Ryosuke Sato (Weizmann Institute of Science) based on arxiv: [astro-ph.he] Kfir Blum, Kenny C.Y. Ng, RS, Masahiro Takimoto TeVPA 2017 [ 1 / 14 ]

2 AMS-02 observed Anti-Helium3? In 2016 Dec, AMS-02 announced, we have observed a few events with Z=-2 and with mass around 3He. [taken from S. Ting s slide] [ 2 / 14 ]

3 AMS-02 observed Anti-Helium3? In 2016 Dec, AMS-02 announced, we have observed a few events with Z=-2 and with mass around 3He. Folklore : Astrophysical anti-he3 flux is super low, and it is much much below the sensitivity of AMS-02. See e.g., [Chardonnet et al (1997)] [Duperray et al (2005)] [Cirelli et al (2014)] [Herms et al (2016)] [taken from S. Ting s slide] [ 3 / 14 ]

4 AMS-02 observed Anti-Helium3? In 2016 Dec, AMS-02 announced, we have observed a few events with Z=-2 and with mass around 3He. Folklore : Astrophysical anti-he3 flux is super low, and it is much much below the sensitivity of AMS-02. See e.g., [Chardonnet et al (1997)] [Duperray et al (2005)] [Cirelli et al (2014)] [Herms et al (2016)] Summary of my talk : Q : Is secondary flux of anti-he3 below AMS-02 sensitivity? A : Not really. Secondary CR Anti-Helium3 could be observed by AMS-02. [taken from S. Ting s slide] [ 4 / 14 ]

5 Secondary production in our galaxy p p e +, p, d, He 3, n He 3 n p = X esc /m 1 + n He 3/n p σ He 3/m σ pp He 3 [Dogiel, Berezinsky, Bulanov, Ptsukin (1990)] [Gaisser, Schaefer (1992)] [Blum, Katz, Waxman (2009, 2013)] σ He 3 : fragmentation cross section of antihelium3 X esc (R) is determined from Boron-Carbon ratio. The production cross section is important! [ 5 / 14 ]

6 Cross section for nuclei production Coalescence anzats : Nucleons (p, n) which travels (almost) same direction forms nuclei 3He p p n p p d 3 σ A E A dp 3 = B d 3 σ N A E N dp 3 A p N =p N /A B A is (almost) independent on other parameters (e.g., s, p t, η). B A should be determined from the experiment. Anti-deuteron : ISR (pp collision at s = 53 GeV) Anti-Helium3 : No pp collision data! (except for ALICE 7 TeV preliminary result) Heavy ion collision gives information. [ 6 / 14 ]

7 Volume scaling of BA [See e.g., Csernai and Kapusta (1986)] Q : B A at pp collision and B A at heavy ion collision should be same? A : No. It depends on the size of interaction region (fireball). B A ρ A 1 V A+1 ρ : number density of fireball V : fireball volume p p Pb Pb B A in heavy ion collision < B A in pp collision [ 7 / 14 ]

8 Volume scaling of B2 : anti-deuterium Radius of fireball by HBT measurement [Blum, Ng, Sato, Takimoto(2017)] [ 8 / 14 ]

9 Volume scaling of B2 : anti-deuterium proton-heavy ion Roughly, Scaling law for B 2 works. proton-proton Heavy ion-heavy ion [Blum, Ng, Sato, Takimoto(2017)] Radius of fireball by HBT measurement [ 9 / 14 ]

10 Volume scaling of B3 : anti-helium 3 [Blum, Ng, Sato, Takimoto(2017)] Radius of fireball by HBT measurement [ 10 / 14 ]

11 Volume scaling of B3 : anti-helium 3 Size of fireball in pp collision proton-heavy ion We estimate B 3 = GeV 4 for pp collision Heavy ion-heavy ion [Blum, Ng, Sato, Takimoto(2017)] Radius of fireball by HBT measurement [ 11 / 14 ]

12 Anti-Helium3 flux [Blum, Ng, Sato, Takimoto(2017)] Chardonnet 1997 Duperray 2005 Cirelli 2014 Ibarra-Wild 2012 Herms 2016 : p c which is derived from d for He3. using different pp d X data. : B parameter from pa/aa collisions. : PYTHIA : PYTHIA & DPMJET-III : PYTHIA & DPMJET-III [ 12 / 14 ]

13 Number of anti-helium3 events at AMS-02 5 yrs Our estimation on B3 [ 13 / 14 ]

14 Summary Secondary production of anti-he3 is reconsidered Coalescence parameter of pp collision should be smaller than AA Astrophysical antihe3 could be within the reach of 5-yr AMS-02 Stay tuned for official AMS-02 paper. We need direct measurement on B 3! To calculate antinuclei flux coalescence parameter B A is the most important. ALICE and LHCb could be important to measure B 3. [ 14 / 14 ]

15 Backup

16 HBT measurement and emission volume How to measure the size of emission region. [Hanbury-Brown, Twiss (1954)] Correlation function of intensity fluctuation : C = δi p 1 δi p 2 δp 1/R different phase space (no interference) C = 0 δp < 1/R same phase space (interference) C 0 C size : R δp Intensity corr. of π ±, K ±, p, p etc. at pp, pa, AA collision size of fireball

17 Antimatter flux [Blum, Ng, Sato, Takimoto(2017)] Chardonnet 1997 Duperray 2005 Cirelli 2014 Ibarra-Wild 2012 Herms 2016 : p c which is derived from d for He3. using different pp d X data. : B parameter from pa/aa collisions. : PYTHIA : PYTHIA & DPMJET-III : PYTHIA & DPMJET-III

18 Anti-Helium3 at the LHC We estimated B 3 (pp) from B 3 (AA). Direct measurement on B 3 (pp)? ALICE preliminary analysis ( ) says, s = 7 TeV L 2.2nb 1 ALICE measurement Estimaton from HBT measurement [Blum, Ng, Sato, Takimoto(2017)]

19 Volume scaling [See e.g., Csernai and Kapusta (1986)] Non-relativistic case W p, x = 2π 3 d 6 N dx 3 dp 3 W p, x = 2π 3 V d 3 N dp 3 If we can neglect the size of particles, W p, x = c W p p/a, x Z W p p/a, x N d 3 N dp 3 = c 2π 3 V A 1 d 3 N dp 3 Z d 3 N dp 3 N

20 Anti-d observation at pp collision ISR (1970 s) Serpukhov (1987) s = 53 GeV p t < 1 GeV B GeV 2 s = 11.6 GeV p t > 1 GeV B GeV 2

21 Pythia versus Coalescence formula

22 How to calculate secondary CR flux Assumptions : [Dogiel, Berezinsky, Bulanov, Ptsukin (1990)] [Gaisser, Schaefer (1992)] [Blum, Katz, Waxman (2009, 2013)] 1. Same rigidity (R = p/z) gives same trajectory in magnetic field. 2. Neglect energy loss (I will not discuss e + today) 3. Composition is same in every point in which production is active n B R; x, t = dt d 3 x ρ ISM x, t P(R; x, t, {x, t })Q B R; x, t ρ ISM : ISM density P : probability to reach the earth : source term Q B Q B = σ C B m ISM n C σ B m ISM n B

23 How to calculate secondary CR flux Assumptions : [Dogiel, Berezinsky, Bulanov, Ptsukin (1990)] [Gaisser, Schaefer (1992)] [Blum, Katz, Waxman (2009, 2013)] 1. Same rigidity (R = p/z) gives same trajectory in magnetic field. 2. Neglect energy loss (I will not discuss e + today) 3. Composition is same in every point in which production is active n B R; x, t = dt d 3 Q B R; x, t x ρ ISM x, t P R; x, t, x, t Q B R; x, t Q B R; x, t ρ ISM : ISM density P : probability to reach the earth : source term Q B Q B = σ C B m ISM n C σ B m ISM n B

24 How to calculate secondary CR flux Assumptions : [Dogiel, Berezinsky, Bulanov, Ptsukin (1990)] [Gaisser, Schaefer (1992)] [Blum, Katz, Waxman (2009, 2013)] 1. Same rigidity (R = p/z) gives same trajectory in magnetic field. 2. Neglect energy loss (I will not discuss e + today) 3. Composition is same in every point in which production is active n i R; x, t = n CR x, t f i (R) n B R; x, t = dt d 3 n CR x, t x ρ ISM x, t P R; x, t, x, t Q B R; x, t n CR x, t universal for all elements (function of R) ρ ISM : ISM density P : probability to reach the earth : source term Q B Q B = σ C B m ISM n C σ B m ISM n B

25 How to calculate secondary CR flux Assumptions : [Dogiel, Berezinsky, Bulanov, Ptsukin (1990)] [Gaisser, Schaefer (1992)] [Blum, Katz, Waxman (2009, 2013)] 1. Same rigidity (R = p/z) gives same trajectory in magnetic field. 2. Neglect energy loss (I will not discuss e + today) 3. Composition is same in every point in which production is active n i R; x, t = n CR x, t f i (R) We can define X esc R [g/cm 2 ] such that n B Q B = n p Q p = n d Q d = n 3He Q 3He = = X esc R ρ ISM (x, t ) This relation is model-independent relation. supported by the measurement of stable nuclei. [Webber, McDonald, Lukasiak (2003)]

26 Exercise : antiproton / proton ratio [Blum, Ng, Sato, Takimoto(2017)]