Searching for Cosmological Antimatter Bob Streitmatter For the BESS Collaboration (KEK / NASA-GSFC / Tokyo / Kobe / Maryland / ISAS) Outline

• Briefly: (TEE), Theory Explained by Experimentalist • Review History of Experimental Search for CAM • Instruments, Techniques and measurements • BESS Program • Current Status of Data •The Future In the Beginning …

•Dirac, in 1928, was the first to realize that the physics of relativity and quantum mechanics taken together required the existence of matter whose additive quantum numbers (e.g. charge, baryon number, lepton number, spin) were the negative of “normal” matter. (Proc. R. Soc. London, A, 117, (1928), 610)

•Positron discovered, August 2, 1932. Positron produced by cosmic radiation seen in a cloud chamber. (Anderson, Phys. Rev. (1933) 491) Baryon Symmetric Universe

“We must regard it rather as an accident that the Earth and presumably the whole Solar System contains a preponderance of negative electrons and positive protons. It is quite possible that for some of the stars it is the other way about”

-- Dirac, 1933 Noble acceptance speech Antimatter Miscellanea

• 1955: Antiprotons are “manufactured” at Bevatron - Chamberlain et al. Phys. Rev. 100 (1955) 947

• Experimental evidence that antimatter is normal in the gravitational sense - High and Holzschieter Phy. Rev. Lett. 66 (1991) 854

• Contrary to popular myth among Trekkies, the 1908 Tunguska meteor was not antimatter - Cowan, Atluri and Libby, Nature, May 29, 1965 But: Simple Big Bang BSU Fatal Problems

•The “Annihilation Catastrophe” - not enough baryons •SBB predicts baryon/photon ratio ≈ 10-18 at freezeout •Observed baryon/photon raio ≈ 10-9

•How did the matter and antimatter get separated? •Fluctuations won’t do it •e.g. Kolb and Turner, Ann. Rev. Nucl. Part. Sci. 33 (1983) 645 •No viable “mechanism” for separation ever suggested Sakharov’s Solution to the BSU Problem

The Universe doesn’t have to be baryon symmetric IF: 1) Direct violation of baryon number conservation “X” particle decay breaks baryon symmetry 2) CP symmetry is violated

If CP not violated, “mirror” antiparticle decays will compensate and maintain overall net baryon number 3) Universe must have a period out of thermal equilibrium

Otherwise inverse processes will compensate and maintain overall net baryon number

- Sakharov, JETP Lett. 5 (1967) 24 Maybe It’s Symmetric After All

•The Sakharov conditions offer a way to explain the apparent baryon asymmetry of the Universe •BUT, they also offer the possibility for the separation of matter and antimatter. •Is the sign of CP violation universal, built into the rules? Or is the sign of CP violation local, spontaneous, with domain of matter and antimatter existing? -Brown and Stecker, Phys. Rev. Lett. 43 (1979) 315 - Sato, Phys. Lett. B, 99 (1981) 66 Status of the Sakharov Conditions

1) NO baryon-number-violating decay has been seen 2) CP violation is seen Kaons - Christianson et al., Phys. Rev. Lett., 13 (1964) 138 ==> B NEW BABAR RESULT <== 3) Thermal nonequilibrium OK Chronology

1928 Dirac theory 1932 Positron discovered 1955 Antiprotons “manufactured” 1930s-1960s: BSU cosmologies in fashion - Alfven, Reviews of Modern Physics 37 (1965) 652 1965 Microwave Background, Big Bang dominant 1967 Sakharov conditions 1960s Begin antimatter searches in cosmic radiation 4” x 6” Emulsion Stack, Balloon-borne

“Finally, we would like to point out the following conclusion. Namely, there has been no single case of antiparticles among the observed stopping particles of about 500 alpha particles, 300 (C, N, O), and heavier elements, and more than 1000 singly charged particles. Even with a somewhat larger interaction cross section of antiparticles, this will set an upper limit for the amount of antimatter the the primary radiation at about 0.1%.”

Aizu et al., Phys. Rev. ≈ 500 MeV/n 121 (1961) 1206 Count δ-rays, measure residual range Emulsion Stack with SC Magnet

•1 foot diameter superconducting magnet •Emulsion ≈ 4” x 6” x 10” •Z > 3 Nuclei •Rigidity (P/Z): •4 - 125 GV •8 hours at 120,000 ft.

-3 •FAN < 5 x 10

Golden et al., ApJ 192 (1974) 747 Permanent Magnet with Spark Chambers

•Rigidity (P/Z) + dE/dX •80 cm detector array, with TOF •Z = 2 •0.2 - 4.3 GeV/n

-3 •Upper limit FAHe = 1.4 x 10

Evenson, ApJ 176 (1972) 797 Permanent Magnet + Spark Chambers

-5 FAN < 8 x 10 , rigidity 4 -33 GV/c

Smoot, Buffington and Orth, Phys. Rev. Lett. 35 (258)1975 Instruments of Some Complexity

Smith et al., Rev. Sci. Instru. 43 (1972) 1 Antiprotons Reported, 1979

• P-bar/P ratio • 5 x 10-4 • Rigidity interval 5.6 -12 GV/c

• “ratio consistent with secondary production” (in the ISM) - - a little high Golden et al., Phys. Rev. Lett. 43 (1979) 1196 Antiprotons by Deduction

• “Negative” deflection • It’s not an electron or muon (no-Cherenkov) • Must be an antiproton

Golden et al., Phys. Rev. Lett. 43 (1979) 1196 Antiprotons Reported, 1979

• P-bar/P ratio • 6 x 10-4 •2-5 GeV

Bogomolov et al., Proc. 16th ICRC, Kyoto 1 (1979) 330 Antiprotons Reported, 1981

• P-bar/P ratio • 2.2 x 10-4 • 130 - 330 MeV

• NOT consistent with secondary production

Buffington, Schindler and Pennypacker, ApJ 248 (1981) 1179 Antiproton by Annihilation Signature

Buffington, Schindler and Pennypacker, ApJ 248 (1981) 1179 Antiprotons in CR, 1980s

Uncertainty

Streitmatter et al., Adv. Space Res. 9 (1989) (12)69 But Anti-galaxies Are Not the Only (possible) Source Now that there are antiproton measurements (ca. 1980) what do they mean?

•And there is a background of antiprotons produced in the atmosphere ! Go to Space: No Atmosphere, Long Duration

HEAO: used geomagnetic cutoff

-4 FAN Z > 9, 1.5 10 , ≈ 2 - 11 GeV/n

Lund and Rothenberg Astron. Astrophys. 164 (1986) 231 Astromag Influence on Spectrometers Isotopes Antimatter SMILI LEAP MASS PBAR IMAX MASS BESS IMAX CAPRICE BESS ISOMAX TS93 PAMELA CAPRICE HEAT PAMELA Chronology

1979: First observation (Golden et al) 2004: BESS-Polar 1979: Russian PM (Bogomolov et al) 2005: PAMELA 1981: Low-energy excess (Buffington et al) 2006: BESS-Polar 1985: ASTROMAG Study Started 2007: Solar minimum 1986: HEAO Antinucleus upper limits 2008: AMS-02 1987: LEAP, PBAR (upper limits) 1991: MASS 1992: IMAX (16 mass-resolved antiprotons) 1993: BESS (6 mass-resolved antiprotons) 1994: CAPRICE94 1996: Solar minimum 1998: CAPRICE98, AMS-01 2000: HEAT-pbar WiZard Balloon Program: CAPRICE94/98 Cosmic AntiParticle Ring Imaging Cherenkov Experiment U. Bari, Tata Institute of Fundamental Research, U. Firenze, Laboratori Nazionali INFN di Frascati, NASA/Goddard Space Flight Center, New Mexico State U., U. Tor Vergata (Rome), U. Siegen, Royal Institute of Technology, Centre des Recherches Nucleaires, U. Trieste TOF: flight direction, β, charge Spectrometer: charge sign, momentum Si Imaging Calorimeter: electron/hadron separation CAPRICE94: NaF proximity focused RICH 0.6-3.2 GeV p CAPRICE98: Mirror focused gas RICH 3-49 GeV p

p events 20-50 GV HEAT (High Energy Antimatter Telescope)

U of Chicago, Eastern New Mexico U., Indiana U., UC Irvine, U. of Michigan, Washington U. St. Louis

U of Chicago, Northern Kentucky U., Indiana U., U. of Michigan, Penn State U., U. Minnesota TOF: flight direction, β, charge Spectrometer: charge sign, momentum HEAT-pbar: multiple dE/dx: p / π-µ / e separation 4-50 GeV p HEAT-e±: PID by TRD and Electromagnetic Calorimeter

Negative rigidity Positive rigidity BESS Collaboration (from 1992 to present) (Balloon Experiment with a Superconducting Spectrometer) • High Energy Accelerator Research Organization (KEK) A. Yamamoto, H. Fuke, T. Kumazawa, K. Matsumoto, Y. Makida, H. Omiya, J. Suzuki, K. Tanaka, T. Yoshida, K. Yoshimura • NASA Goddard Space Flight Center J.W. Mitchell, T. Hams, A. Moiseev, J.F. Ormes, M. Sasaki, A. Stephens, R. Streitmatter • The University of Tokyo Y. Asaoka, K. Anraku, M. Fujikawa, S. Haino, M. Imori, K. Izumi, S. Matsuda, N. Matsui, H. Matsumoto, H. Matsunaga, M. Motoki, J. Nishimura, S. Orito*, T. Saeki, T. Sanuki, T. Sonoda, I. Ueda, Y. Yamamoto • Kobe University K. Abe, N. Ikeda, A. Itazaki, T. Maeno, T. Matsukawa, T. Mitsui, M. Nozaki, A. Ogata, M. Oikawa, Y. Shikaze, Y. Takasugi, K. Takeuchi, K. Tanizaki, K. Yamato • Institute of Space and Astronautical Science Y. Yajima, T. Yamagami • The University of Maryland M.H. Lee, K.C. Kim, Z.D. Myers, E.S. Seo, J.Z. Wang * Deceased BESS Measurement Technique

Particle identification by mass and charge β-1 Charge-sign from deflection direction

- +

- +

Rigidity •Superconducting magnetic spectrometer: measures momentum (R = P/Ze) •Precision time-of-flight system: measures velocity and charge RZe •Silica-aerogel Cherenkov detector: background rejection m = γβc BESS Antiproton Measurements 1993 - 2002 Antiproton-Events-by-2000-t •BESS has carried out nine 2500 each year successful flights since 1993 integrated 2000 •Since 1997, 400-600 antiprotons Aerogel Cherenkov Counter 1997-2002 recorded in each 1-day flight 1500 n=1.03 1.02 •BESS has recorded more than 1000 2400 antiprotons through 2002

Antiproton Events First Flight 500 1993

0 1993 1994 1995 1996 1997 1998 1999 2000 2001 Year Evolution of the BESS Instrument BESS Particle Identification Evolution

• PID (charge and mass) by dE/dx together with

βTOF vs. Magnetic Rigidity

• 1993/1994 σTOF 280 ps

• 1995 σTOF 110 ps

• 1997 σTOF 75 ps BESS ‘97 BESS ‘97 TOF and TOF,dE/dx • 1997 Aerogel Cherenkov dE/dx and Ck Counter added to suppress background from light particles Data Accumulation With Successive Flights

1993 1994 1995 1997 1998 1999 2000 DAQ (hrs) 14.0 15.0 17.5 18.3 20.0 31.3 32.5 Rec’d Event 4.0 4.2 4.5 16.2 19.0 16.8 15 (M Events) # of 6 2 43 415 384 668 558 Antiprotons Antiproton 0.18~0.5 0.18~1 0.18~3. 0.18~4.2 PID (GeV) .5 6 He/He 2.2×10-5 4.3×10-6 2.4×10-6 1.4×10-6 8.8×10-7 6.7×10-7 BESS An Instrument of Some Complexity Understanding Solar Modulation with BESS

Field Reversal

Negative Positive Negative Positive Polarity Polarity Polarity Polarity • Solar magnetic field 22 year cycle

• Sunspot Number 11 year cycle

• Neutron Monitor 11year cycle

• BESS data already 2000 covers 9 years Modulation of P-bar and P Flux Measured With BESS

The drift model explains the ratio, but still needs to be fine-tuned. Asaoka et al., Phys.Rev.Lett. 88 (2002) 051101-1 Atmospheric Antiprotons Measured With BESS

• Balloon altitude • Mountain altitude • Sea level

• Agrees with the calculation of Stephens, Astropart. Phys. 6 (1997) 229

Nozaki et al, COSPAR 2004 Sanuki et al., Phys. Lett. B 577 (2003) 10 BESS Antiproton Energy Spectrum -1 1010-1 – Cosmic Ray P Characteristic spectral peak for secondary antiprotons ~2 GeV BESSBESS(95+97) (95+97) BESSBESS(93) (93) Best current calculations and BESS IMAIMAXX CAPRICE spectra agree to 10-15%

) CAPRICE -1 )

-1 Primary + GeV Some excess at low energy? Secondary -1 GeV -1 sec -1

sec Due to “Exotic” source??

sr -2

-1 -2

2 1010 - sr -2 Long duration (high statistics) Secondary Spectrum flux (m (Model) observations at low energy are flux (m – p Pbar 1 Mitsui λ(R,β) φ=550MV crucial to answer this question!! Mitsui φ = 550 MV 2 PBH φ=550MV PBH φ = 550 MV φ 3 Mitsui+PBHMitsui+PBH φ = 550=550MV MV 4 MitsuiMitsui λ (R, βφ)= φ100=1000MV0 MV New instrument designed for Antiprotons from 5 PBHPBH φ = φ1=1000MV000 MV PBH decay 6 Mitsui+PBHMitsui+PBH φ =φ 1=1000MV000 MV long-duration, high-latitude 10-3 -3 flight (BESS-Polar) . 10 -1 1010-1 11 1010 Kinetic Energy (GeV) Kinetic Energy (GeV) (S. Orito et al. PRL, Vol. 84, No. 6, 2000) BESS-Polar: Lower Energy, High Statistics

•Measurements to lower energy. • Reduced geomagnetic influence • 75% less material in particle path!! •Long Duration Flight • Technical flight Fall 2003 completed • Antarctic flight Winter 2004-2005 • Antarctic Flight Winter 2006-2007 • More than double present p statistics in first flight - 6 times in two flights • ~22 times present solar-minimum p statistics in 2006-2007 flight Ultra-thin superconducting magnet

Equivalent stress on the solenoid @ 1.2 T Well below the yield strength of high strength SC Eliminate thick support cylinder 2 3.4mm, 0.056 X0 (1.0 g/cm ) Total materials including cryostat 2 2 0.2 Xo (4 g/cm ) Î 0.1 Xo (2 g/cm ) Longer life with larger LHe reservoir > 10days with 400 liter LHe

BESS BESS–Polar 1.2×1.8 0.8×1.1 BESS-Polar Magnet: Thin Solenoid Coil

1 g/cm2 / coil The PAMELA Apparatus ToF

TRD

Anticoincidence Magnetic shield spectrometer

Calorimeter Shower tail catcher scintillator Neutron Detector From Aldo Morselli, Bari Workshop, June 21, 2004 PAMELA Capabilities

PAMELA will explore: Antiproton flux 80 MeV - 190 GeV Positron flux50 MeV – 270 GeV Electron flux up to 400 GeV Proton flux up to 700 GeV Electron/positron fluxup to 2 TeV Light nuclei (up to Z=6) up to 200 GeV/n Antinuclei search (sensitivity of 10-7 in He/He)

more on PAMELA:http://wizard.roma2.infn.it/ AMS-01

• Flew on Shuttle-91 in June 1998 • Antihelium/helium limit in rigidity range 1-140 GV/c: 1.1 x 10-6

Aguilar et al., Phys. Reports. 366 (2002) 331 AMS-02

•Full detector set • TRD, TOF, RICH, Cal • Currently scheduled for ISS in 2008 BESS-Polar Complements

Space-Based Instruments Program PA MEL A AMS BESS- Polar Acceptance 0.0021 0.5 0.3 3 years (m2•sr) MDR (GV) 740 ~1000 150

Particle ID TOF, TRD, TOF, TRD, TOF, CAL RICH, CAL ACC 20 days Flight time 1000 1000 20 (days) Altitude 690 320~390 36 (km) 3 years Latitude 70.4 < 51.7 > 63 (deg) Near-polar Space Station Polar Orbit Balloon. Launch 2005 2008 2004

BESS-Polar has high sensitivity in low-energy region. Search for Antihelium

Progress in BESS93~00 Upper Limit: He/He: 7 x 10-7 BESS-Polar: Sensitivity: He/He: 3 x 10-8 (30 days) BESS-Polar: Precise Antiproton Spectra

BESS95+97 (solar min ~1-day/year) BESS-Polar (20-day solar-min flight shown)

BESS95+97 p Secondary

Primary Origin ?

PAMELA

•BESS-Polar: > 103 p @ <1 GeV • Sufficient statistics to search for antiprotons of “exotic” origin Search for Antideuteron

H. Fuke, Thesis

• Secondary D probability is negligible at low energies due to kinematics • Any observed D probably has a Primary Origin ! • D upper limit (first reported), 1.92 x 10-4 (m2 s sr GeV/n)-1 Technical Flight at Ft. Sumner NM October 2003 BESS-Polar Spectrometer Snapshots BESS-Polar Integration at NASA/GSFC July 15, 2004 BESS-Polar Integration at NASA/GSFC Complete: August 3, 2004 The end

BESS in Canadian Waters

Soon, BESS On Antarctic Ice