Antimatter: from atomic physics to cosmology Michael Doser CERN 1905 1925 Special Relativity Quantum Mechanics 1927 1932 Dirac Equation Positron every particle has an antiparticle the properties of the antiparticle are identical to those of the particle (except that its charges have the opposite sign) pair production of particles and antiparticles However, the Universe is unexpectedly not symmetric Matter Antimatter Why is the Universe lopsided? How can the absence of antimatter be explained? Baryon asymmetry Search for antimatter Study antimatter Antiprotons, positrons in cosmic rays; Investigate symmetries and Positron-electron annihilation in space try to find an asymmetry 1905 1925 at Special Relativity Quantum Mechanics CERN 1927 1932 Dirac Equation Positron 1955 1948 Antiproton 1956 accelerator developments Positronium Antineutron 1965 1956-1990’s 1970’s: Antideuteron Scattering, annihilation, accumulation, cooling meson spectroscopy 1970 1980’s: 3 _ Anti- He colliders (SppS, LEP, Tevatron) 1980’s - now 1978 W, Z, b, t physics Anti-tritium 1983 - 1996: 1996: hot (v~c) trapping LEAR antihydrogen Primordial antimatter, 2000 - now Anti-stars cold antihydrogen AD trapped cold antihydrogen use these technologies to: produce and trap stable (anti)particles, combine them to form (anti)atoms carry out precision measurements of their properties Search for some form of asymmetry between matter and antimatter : CP and CPT do particles (atoms) have the same properties as antiparticles (antiatoms) ? Motivation Precision measurements with Antimatter: 1) Precise comparison between matter and antimatter test of fundamental symmetry (CPT - Charge, Parity, Time) comparing antiprotons with protons, electrons with positrons, and hydrogen with antihydrogen 2) Measurement of the gravitational behavior of antimatter test of the Weak Equivalence Principle impossible to work with charged (anti) particles; only neutral systems (atoms) are sensitive enough Motivation: CPT Goal of comparative spectroscopy: test CPT symmetry Hydrogen and Antihydrogen ):%30(&/ %30(&/ : ) 1 1 4 4 1s-2s 2 photon 1 1 !=243 nm T. Hänsch et al., -14 Phys. Rev. Lett. 84, 5496–5499 (2000) "f/f=10 ' ' 4 4 Stefan Meyer Institute ' ' #PIS %JSBD -BNC )'4 )'4 -BNC BD %JS PIS # Ground state hyperfine splitting f = 1.4 GHz N. F. Ramsey, -12 Physica Scripta T59, 323 (1995) "f/f=10 E. Widmann 64 Atomic physics with anti-atoms Motivation: CPT Verifications of CPT symmetry Tests of particle/antiparticle symmetry (PDG) absolutabsolutee accur accuracyace (G eV[GeV]) 10−27 10−24 10−21 10−18 10−15 10−12 10−9 10−6 10−3 100 H-H GS-HFS planned H-H 1S-2S K0-K0 mass p-p mass, chargecharge p-p charge/massratio e± mass Stefan Meyer Institute µ± g-factor e± g-factor 10−27 10−24 10−21 10−18 10−15 10−12 10−9 10−6 10−3 100 relative accuracy Inconsistent definition of figure of merit: comparison difficult AbsoluteInconsistent energy definition scale: standard of figure ofmodel merit: extension comparison (Kostelecky) difficult PatternPattern of of CPT CPT violation violation unknown unknown (P: (P: weak weak interaction, interaction; CP: CP: mesons) mesons) Absolute E.energy Widmann scale: standard model extension (Kostelecky PRL 82, 225446 (1999)) Gravity Motivation: WEP General relativity is a classical (non quantum) theory Some quantum gravity theories allow WEP violations New quantum fields (scalar, vector) are allowed in some models (Kaluza Klein, ... ), resulting in new interactions that may violate the equivalence principle Matter-matter interactions have been probed extensively Matter-antimatter interactions have never been probed Gravitational physics with anti-atoms CERN Accelerator Complex Antiproton decelerator ( 1013 p @ 26 GeV/c2) _ AEgIS ATRAP ASACUSA ALPHA The challenge: Making Antihydrogen Route A: Route B: Trapping Antihydrogen Forming a beam of Antihydrogen Cooling Antihydrogen Studying Antihydrogen Studying Antihydrogen 1000K 1K ASACUSA ALPHA _ ATRAP 1μV 1mK AEgIS Typical Antihydrogen Experiment • Capture, trap, cool antiprantiprotonsotons 107 (AD) ➟105 (trapped) • Capture, trap, cool positrpositronsons 1.5 GBq 22Na ➟108 (trapped) • Merge and recombine 3 to form antihydrogen atoms 1-10 Hz Stefan Meyer Institute E. Widmann 68 Trapping of charged particles Penning trap 2 cm All antihydrogen experiments use this technique _ p e+ _ p e+ _ p e+ _ 2002: first production of H _ p e+ _ Trapping of H? _ Trapping of H? _ H: Confine both charged plasmas and neutral atoms without heating them -Preserve cylindrical symmetry (plasma confinement) -Magnetic field minimal in center (atom confinement = magnetic bottle) -Antihydrogen must be formed inside its trap -Antihydrogen trapped only if its temperature < 0.5K Reaching the few K regime essential to avoid reheating: week ending PRL 105, 013003 (2010) P H Y S I C A L R E V I E W L E T T E R S 2 JULY 2010 - great care needed on noise reduction; particle cloud is in thermal equilibrium, the particles that a) 3 _ are- notinitially easyreleased tooriginate use fromelectronthe exponential cooling_ tail of a to pre-cool10 p Boltzmann- how distributo bringtion [13 e],+so andthat acoldfit can pbe inused contactto without heating either? determine the temperature of the particles. Figure 2 shows six examples of measured antiproton energy distributions. 2 The raw temperature fits in Fig. 2 are corrected by a 10 factor determinedALPHAby particle-in-cell and ATRAP(PIC) simulations haveof solved this plasma thephysicsantiprotons being problemreleased from the afterconfining manypotential. yearsTemperature [K] of work in 2010 The simulations include the effect of the time dependent 1 10 Data vacuum potentials and plasma self-fields, the possibility of Model evaporation, and energy exchange between the different 1 2 3 week ending translational degrees of freedom. The simulations suggest 10 PRL 105, 01300310(2010) 10P H Y S I C A L R E V I E W L E T T E R S 2 JULY 2010 evaporative cooling of antiprotonsweek ending (ALPHA) PRL 105, 013003 (2010) P H Y S I C A L R E V I E W thatL EtheT TtemperatureE R S determined from the2 JULfitY is2010 16% On−axis well depth [mV] higher than the true temperature. Note that the PIC-based Evaporative Cooling of Antiprotons_ to Cryogenic Temperatures particle cloud is in thermal equilibrium, the particles that a) correction3 has been applied to all temperatures reported in b) this10 Letter. The distribution labeled A in Fig. 2 yields a 100 %1 45‘000 p are initially released originate from the exponential tail of a 1000 K G. B. Andresen,1 M. D. Ashkezari,2 M. Baquero-Ruiz,3 W. Bertsche,4 P. D. Bowe,1 E. Butler,4 C. L. Cesar,5 S. Chapman,3 Boltzmann distribution [13], so that a fit can be used to corrected temperature of 1040 45 K before evapora- 4 3 6 7 7 1 8 9 ð Æ Þ 1.5 V 0.8 M. Charlton, J. Fajans, T. Friesen, M. C. Fujiwara, D. R. Gill, J. S. Hangst, W. N. Hardy, R. S. Hayano, determine the temperature of the particles. Figure 2 shows tive cooling; the others are examples of evaporatively M. E. Hayden,2 A. Humphries,4 R. Hydomako,6 S. Jonsell,4,10 L. Kurchaninov,7 R. Lambo,5 N. Madsen,4 S. Menary,11 cooled antiprotons achieved as described below. 12 7 7 3 12 13 14 15,16 3 six examples of measured antiproton energy distributions. 2 P. Nolan, K. Olchanski, A. Olin, A. Povilus, P. Pusa, F. Robicheaux, E. Sarid, D. M. Silveira, C. So, 10 0.6 The raw temperature fits in Fig. 2 are corrected by a 100 KTo perform evaporative cooling, the depth of the initially J. W. Storey,7 R. I. Thompson,6 D. P. van der Werf,4 D. Wilding,4 J. S. Wurtele,3 and Y. Yamazaki15,16 factor determined by particle-in-cell (PIC) simulations of 1500 mV deep confining well was reduced by linearly 50 % 0.4 ramping the voltage applied to one of the electrodes to the antiprotons being released from the confining potential. Temperature [K] 10 mV (ALPHA Collaboration) The simulations include the effect of the time dependent one of six different predetermined values [see examples on Fraction remaining 1 Data 0.2 Data _ vacuum potentials and plasma self-fields, the possibility of Fig.10 1(b)]. Then the antiprotons were allowed to reequili- 1Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark Temperature 10 K Model 2 Model 2’500 p brate for 10 s before being ejected to measure their tem- Department of Physics, Simon Fraser University, Burnaby BC, V5A 1S6, Canada evaporation, and energy exchange between the different 3 fraction remaining fraction 0 perature and1 remaining number2 . The shallo3 west well 0 % 1 Department2 of Physics, University3 of California at Berkeley, Berkeley, California 94720-7300, USA translational degrees of freedom. The simulations suggest 10 10 10 10 10 4Department 10of Physics, Swansea University, Swansea SA2 8PP, United Kingdom that the temperature determined from the fit is 16% investigated10 had a depth 100of 10 4 mV1000. Since only one 10 1005 1000 On−axis well ðdepthÆ [mV]Þ On−axis wellInstituto depth [mV]de Fı´sica, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-972, Brazil higher than the true temperature. Note that the PIC-based side of the confining potential is lowered, the evaporating 6Department of Physics and Astronomy, University of Calgary, Calgary AB, T2N 1N4, Canada antiprotons are guided by the magnetic field onto the 7TRIUMF, 4004 Wesbrook Mall, Vancouver BC, V6T 2A3, Canada correction has been applied to all temperatures reported in b) FIG. 3. (a) Temperature vs the8 on-axis well depth. The error is this Letter. The distribution labeled A in Fig. 2 yields a aluminum1 foil, where they annihilate. Monitoring the an- Department of Physics and Astronomy, University of British Columbia, Vancouver BC, V6T 1Z1, Canada on-axis well depth [mV] the combinedon-axisstatistical uncertainty well fromdepththe temperature 9[mV]Departmentfit ofandPhysics, University of Tokyo, Tokyo 113-0033, Japan corrected temperature of 1040 45 K before evapora- nihilation signal allows us to calculate the number of an uncertainty associated with the applied potentials10 (one ).