KEK I. II. a. BESS b. c. d. III. BESS-Polar IV.
Introduction
D
p GeV (<1GeV )
D B.G. free D (Fuke et al.) D D D (<1GeV/n)
LSP WIMP Dark Matter χ jet fragmentation D K.Mori et al, APJ 566 (2002) 604
PBH PBH D
D BESS 1997-2000 : σ t C
BESS Detector
BESS Spectrometer BESS 99 T ~ 0.3m 2 sr, ~8-10 g/cm 2 / wall Rigidity (=Pc/Ze), β (σ t ~70ps), de/dx
Trigger
Balloon Flights
BESS Balloon Flight Launch up to ~36km (~5mbar) BESS spectrometer ~200m
Data Taking Live Time (hr) Mean Air Depth (g/cm 2 ) 1997 1998 1999 2000 15.8 16.8 27.4 28.7 5.4 5.2 3.9 5.9
Analysis
Event Selection Pre-Selection single track downward going fully contained N TOF = 1 or 2 Upper TOF de/dx Quality Cut trajectory fitting Paticle Identification de/dx vs Rigidity 1/β vs Rigidity Aerogel Chrenkov OK NG
Fiducial Volume
Quality Cuts Hits used in trajectory fitting χ 2 of trajectory fitting Dropped hits Trajectory agreement with IDC hits ( r-φ, z ) Trajectory agreement with TOF hits ( r-φ, z ) (TOF, de/dx)
Particle ID
Upper TOF de/dx dx cut Eliminate recoil deuterons ( fake events ) broad tail in upper de/dx Tighter than lower / JET de/dx
Particle ID
1/β cut
Silica aerogel veto cut eliminate e - /µ - backgrounds especially in high β region (1/β < 1.1) 97 n=1.03 98~ 00 n=1.02
Survived Events No D candidate
Deuteron Samples Number of D samples Rigidity (GV) 1997 7545 < 3.70 1998 7183 < 3.65 1999 8050 < 3.58 2000 5204 < 3.59 Efficiency
Possible Contamination D ( in R >2.3 GV where p 1/β band overlaps D band ) D p ~ 1 event / 4 flights (+3.89σ) ( c.f. ~ 0.1 event / 4 flights (+6σ) ) e - /µ - ~ 0.1 times p contamination p < 0.5 % T < 1 % e + /µ +, He << 0.1 %
Results D
Outline conservative D ( independent ) obs Φ D Ω total live 2 1 N S ε T ( E E )(1 sys. err) min ε = ε ε ε ε ε ε ε ε ε ε total trig rec pre qual d E/dx 1/ β agl acctrk acchit air
Normalization, Correction 3.09 for 95% C.L. upper limit (with null b.g.) obs Φ D Ω total live 2 1 N S ε T ( E E )(1 sys. err) min Monte Carlo simulation (GEANT) Measured by 1 MHz-clock
Normalization, Correction ε = ε ε ε ε ε ε ε ε ε ε total trig rec pre qual d E/dx 1/ β agl acctrk acchit air D sample p sample random p beam M.C.
Cross section Elastic/inelastic cross sections of D scale those of p by hard sphere model σ 1/3 1/3 1/3 1/3 ( Ai, At) Ai + At 0.71( Ai + At ) Inelastic interaction D is fragmented or annihilated 2
Efficiency of Quality Cut Quality cut efficiency basically from Deuteron data. In high-e region, quality cut is essential for p/d separation. Estimated by using both of data and MC. ε qual ε = εqdata ( p) ε qmc qmc ( D) ( p) simulated ε ε qmc qmc ( D) ( p) ε ( p) qdata estimated ε qual
Efficiencies
( ε ) ( ) Systematic errors 2 2 2 2 2 2 SΩ Tlive total SΩ T ε live trig ε ε rec = + + + + SΩ T ε SΩ T ε ε ε live total live trig rec pre 2 2 2 2 2 2 2 ε ε ε ε ε ε ε + + + + + + + ε ε ε ε ε ε ε qual de/dx 1/ β agl acctrk acchit air qual de/dx 1/ β agl acctrk acchit air pre dominant ~ 9 % 2nd largest ~ 6 % 3rd largest ~ 3 % Total ~ 10.4 % The above three efficiencies from MC. Uncertainty in cross sections is not considered ( fixed by the assumption )
Effective exposure factor
D 97-00 1.92x10-4 ( sum ) (m 2 s sr GeV/n) -1 1997 9.82x10-4 1998 8.87x10-4 1999 6.91x10-4 2000 6.24x10-4 0.17-1.15 GeV/n
Discussions
Prediction of D s D s from PBHs Calculation steps Particle emission Coalescence model Source spectrum Interstellar spectrum Solar modulation
Particle Emission dn s 2s dt 2 π [exp( Q/ kt) ( 1) ] d 2 N = N det d = 3 c T 8π GMk M j Γ Q= E dq emission spectrum Γs d g ( Q, E) j jn α j dq 2s j 2 π [exp( Q/ kt) ( 1) ] de antinucleon emission rate 13 10 g GeV T vs. M relation M t 14 u 1/3 5.0 10 ( ) g initial mass of expring PBHs 13.7Gyr
Coalescence model 3 3 3 3 d n 4 d n d d 3 p n 4 n D n 3 p γ = π p 3 0 γ p 3 γ 3 π 0 γ 3 dp 3 dp dp 3 dp 2 Coalescence momentum p 0 = 130MeV/c c.f. Other predictions of D spectra p 0 ~110~160MeV/c A+A accelerator (Low E) p 0 ~140~210MeV/c Theoretically p 0 ~100~400MeV/c PYTHIA/JETSET
Coalescence model
Source Spectrum dn dt 4.2 2 2 T ε ρ h M 1 3 8 3 14 5.2 10 GeV pc 1GeV 10 0.3GeV/cm 5.0 10 g ρ ε h local density of halo dark matter ratio of the density of PBHs with M = M to i ρ h
Interstellar Spectrum Propagation by the Standard Leaky Box 1 λ esc I D QD =, λesc = λesc( R, β) 17g/cm 4πρ m c.f. τ esc λ ρβ c esc 7 = 3 10 yr 2 B/C ratio, C/O ratio
Solar Modulation Numerical calculation of the spherically symmetric model by Fisk. 1 V 2 2 r r 3 r E α ( 2 rs) = ( EU) Modulation parameter from proton spectrum 1997: φ = 500MV 1998: φ = 610MV 1999: φ = 648MV 2000: φ = 1344MV
Solar Activity Climax Neutron Monitor Solar Min. Solar Max. http://odysseus.uchicago.edu/neutronmonitor/
PBH D
Local PBH R PBH T 1 dn dt d T 3.1 ε ρ M 10 pc yr 10 0.3GeV/cm 5.0 10 g 95% C.L. (pc -3 yr -1 ) 97-00 1.8x10 0 sum 1997 5.2x10 0 1998 6.9x10 0 1999 5.7x10 0 2000 2.6x10 1 3 h 3 1 8 3 14 2 c.f. Upper limits on R PBH p ~10-2 TeV-GRB ~10 5-6 Diffuse γ-ray ~10-1
PBH 95% C.L. 1 α dε ε M i =, α = dm M M dε ε Ωh Ω Ω = d 10 0.1 9 PBH h dm i 2.0 10 M 8 M i 97-00 1.2x10-6 sum 5 2 result c.f. Upper limits on Ω PBH p ~10-8 ~ -9 e + /e - ~10-9 Diffuse γ-ray ~10-8
Future Prospects BESS-Polar Tiger Antarctica Flight, 2001/2002
Future Prospects BESS-Polar AMS PAMELA GAPS
BESS-Polar D
BESS-Polar / PAMELA / AMS Sensitivity SΩεt BESS 3 yr 20 days 3 yr
BESS-Polar BESS-Polar
10 1 @ Ft. Sumner
BESS-TeV BESS-Polar
BESS-Polar
D 1.9 x 10-4 (m 2 s sr 2 GeV/n) -1 in 0.17-1.15 GeV/n D BESS 97-00 D D Local PBH PBH BESS-Polar