Risultati recenti di produzione

Risultati recenti di produzione dell anti-idrogeno Luca Venturelli Università di Brescia (Dipartimento di Ingegneria dell Informazione) Istituto Nazionale di Fisica Nucleare Physics Department/INFN joint seminar DIPARTIMENTO DI FISICA, VIA CELORIA 16, MILANO 9 maggio 2014

Antihydrogen Matter Anti-matter particles antiparticles elements anti-elements H Antihydrogenis the simplest atom consisting entirely of antimatter 3

Antihydrogen: whatisitknown? Hydrogen Antihydrogen H 4

Antihydrogen: whatisitknown? Hydrogen Antihydrogen H one of the best understood and most precisely measuredsystem quantity exp. value[hz] ν -15 δ ν δ th exp ν 1s -2s ( ) 2 466061 413187035 10-11 4.2 10 1 10 ν ( ) 3 2s -2p 1 057 8450 29 10 ν 1420 405 751.7667 HFS ( 9) -6-11 2.7 10 3.8 10 3.5 ± 0.9 10-13 -6 6.3 10 ( ) 5

Antihydrogen: whatisitknown? Hydrogen Antihydrogen expected H one of the best understood and most precisely measuredsystem quantity 1s -2s exp. value[hz] δ ν δ th exp ν -15 ν ( ) 3 2s -2p 1 057 8450 29 10 ( ) 2 466061 413187035 10 ν 1420 405 751.7667 HFS ( 9) ν -11 4.2 10 1 10-6 -11 2.7 10 3.8 10 3.5 ± 0.9 10-13 -6 6.3 10 ( ) No precise measurement Why? - Annihilations - Antihydrogen study is young 6

Antihydrogenhistoryisyoung 1980 1990 2000 2010 H ( c) v H (10-100 K) 7

Annihilation Matter-antimatter encounter annihilation Ex.1 Ex.2 electron-positron collision e + γ e Mass converted into energy γ 2 proton-antiproton collision π E = mc p p N.B. Pair production (inverse process of annihilation) permits antimatter production 8

Whystudyantihydrogen 1) Precise matter/antimatter comparison test of CPT symmetry 2) Measurement of the gravitational behaviour of antimatter test of WEP? Impossible with charged antiparticle onlywithneutralsystem H 9

Matter/antimatterasymmetryin the Universe Earth, Moon and planets made of matter Positrons and antiprotons in the cosmics rays are compatible with secondary production (made in the matter collision with the interstellar medium) No primordial antimatter detected 11

t 0 t < 0.001 s equalquantityofmatterand antimatterexpectedfromsymmetry!? All antimatter disappeared and only(part of) matter(and we) survive Possible explanations rely on the fundamental symmetries violations 12

Discrete symmetries: C, P, T Parity transformation P: Inversion of the spatial coordinates ( x, y, z ) ( x, y, z ) Mirror reflection Charge coniugation transformation C: Change of each additive quantum numbers (for example the electrical charge) in its opposite q q Time reversal transformation T: Change the time arrow t t 13

Violationsofthe discrete symmetries In the pastc, P and T transformationswerebelievedtobeexactsymmetries But for Weak interaction: Parity violation SuggestedbyLee & Yang (1956) β-decay experiment by Wu et al (1957) CP violation(1964) K 0 decaysbycronin& Fitch(1964) 14

The CPT theorem 50 s Pauli, Schwinger, Lüders, Jost The CPTtheorem (1954): Any Lorentz-invariant local quantum field theory is invariant under the successive application of C, P and T Assumptions: - flat space-time, Lorentz-invariance, local interactions, unitarity, point-like particles Consequences: - particles/antiparticles: equal mass, lifetime; equal and opposite charge and magnetic moment - atoms/antiatoms: identical energy levels CPT invariance is inside the Standard Model In string theory(and quantum gravity): assumptions non valid CPT violations as a signature of string theory? No measurement of CPT violation exists Luca Venturelli-Risultati recenti di 15

CPT tests: relative & absoluteprecisions absolute precision(left edge) measuredquantity(right edge) = relative precision(length) planned Where CPT violation might appear is unknown 0 0 Considered best CPT test : K K Δm/m ~ 10-18 10 5 Hz but absolute precision could be relevant H H highly competitive Luca Venturelli-Risultati recenti di 16

Test ofcpt symmetry 17

CPT violationin Standard ModelExtension Indiana group, Kostelecky et al. (since 1997) Standard Model can be extended with CPT violation Standard Model Extension (SME) is an effective field theory which contains: - General Relativity - Standard Model -Possibility of Lorentz Invariance Violation -CPT violation comes with Lorentz violation Modified Dirac equation CPT Violating terms Lorentz Invariance Violating terms R.Bluhm, A.Kostelecky, N.Russell, Phys. Rev. Lett. 82, 2254 (1999) - a & b have energy dimensions( absolute comparisons are important) - No quantitative prediction 18

Antihydrogenformation 19

CERN Accelerators LHC: 27 km Antihydrogenexperimentsat AD(Antiproton Decelerator) AD: 188 m Protons: Linac2 (50 MeV) ->ProtonSyncrotonBooster(1.4 GeV) ->ProtonSyncroton(25GeV) ->AD(:antiprotons) 20

Antihydrogenfactory LHC AD PS 21

AntiprotonDecelerator-AD AD is the only source of low-energy antiprotons All-in-one machine: antiproton capture, deceleration& cooling 2 E = mc + E K p + p p + p + p + p p + n p + n + p + p Efficiency: acceleration 10-3 production 10-4 collection(ad) 10-2 total 10-9 AD delivers to the experiments: - 2-4 10 7 antiprotonsper bunch(150-300 nslength) - 1 bunch/ 100 s - Energy = 5.3 MeV(100 MeV/c) 22

The experimentsat AD Experiments: -(2014) ALPHA, ATRAP, ASACUSA, ACE, AEgIS, BASE - ATHENA (terminated), GBAR(future) 23

Howtoformantihydrogen Recombinationprocesses Radiative recombination + p + e H + hν p Three-body recombination + + + + e + e H + e Two-stage charge exchange -9/2 24

ATHENA, ALPHA, ATRAP, ASACUSA Superposition of e+plasma and pbar cloud Howtoformantihydrogen Recombinationprocesses Radiative recombination + p + e H + hν p Three-body recombination + + + + e + e H + e Two-stage charge exchange ATRAP, AEGIS -9/2 25

Two-stagechargeexchange -Cold antihydrogen( antiproton at rest) - antihydrogen n-state can be controlled by laser (n-antihydrogen=n- Cs*) 26

Radiative and 3-body recombinationrates ATHENA 27

Typicalantihydrogenexperiment: ATHENA Three-body recombination letter to Nature Nature 419, 456-459 (2002) 2.5 cm 10 4 pbars 10 8 e + 3T Radiative recombination antiprotons positrons First cold antihydrogens fromad fromthe experimentwithradioactivesources( 22 Na: 400 M e+/s) Procedure: 1) Trapping and cooling of antiprotons 2) Trapping and cooling of positrons 3) antiprotons& positrons mixing to form antihydrogens 10 7 (AD) 10 4-10 5 (trapped) 1.5 GBq 22 Na10 8 (trapped) 1-1000 Hz 28

(charged) antimattertrap Charged particles are confined by: radially by B and longitudinally by E Penning trap ATHENA trap(2002): 29

Trappingand coolingofantiprotons T=15 K p<10-12 mb Technique developed by TRAP Collaboration 30

Trappingand coolingofpositrons 31

Antiprotonsand positronsmixing 32

Antihydrogenformation When antiprotons and positrons have similar velocities p + + + + e + e H + e + p + e H + hν Antihydrogen escapes from the trap centre and annihilates on the trap wall 33

ATHENA Antihydrogendetection M.Doser-CERN 34

ATHENA Antihydrogendetection M.Doser-CERN 35

ATHENA Antihydrogendetection M.Doser-CERN First antihydrogen detection (2002) Millions of antihydrogens produced 36

2.5 cm Si strips π 10 4 pbars Antihydrogendetection γ 10 8 e + H 10 4 p & 10 8 e + are mixed in Penning trap H form and fly away π H annihilate on trap wall Offline selection of H annihilation: CsI crystals γ π 3T Coincidence in space & time (<5µs) of: p annihilation(charged pion vertex) e + annihilation(2 back-to-back511 kev γ) Antihydrogen detection: field ionization technique ATRAP Coll. 37

AntihydrogenforCPT test matter-antimatter precise comparison by means of spectroscopy directexperimentaltest (no model is required) Plans for antihydrogen: - measurements: - Hyperfine splitting - methods: of ground state - 1S-2S transition - Antihydrogen trapping - Antihydrogen beam 38

AntihydrogenforCPT test matter-antimatter precise comparison by means of spectroscopy directexperimentaltest (no model is required) ALPHA ATRAP Plans for antihydrogen: - measurements: - Hyperfine splitting of ground state - 1S-2S transition -methods: - Antihydrogen trapping - Antihydrogen beam 39

AntihydrogenforCPT test matter-antimatter precise comparison by means of spectroscopy directexperimentaltest (no model is required) ASACUSA AEGIS Plans for antihydrogen: - measurements: - Hyperfine splitting of ground state - 1S-2S transition -methods: - Antihydrogen trapping - Antihydrogen beam 40

Trappedantihydrogenfor1S-2S spectroscopy 41

Antihydrogentrap Broken rotational symmetry: can a Penning trap be superposed? large B-fields needed for pbars trapping, cooling, etc. but large B needed for Hbartrapping 42

ALPHA: first trapofantihydrogen Nature 468, 673 (2010) Fast shutdown of trap magnets (9 ms) Trap depth=0.5k Hbar simulation pbar simulation 38 annihilations in 335 attempts Final number: 1 trapped Hbar per trial Trapped antihydrogen for at least 172 ms 43

ALPHA: trapofantihydrogenfor1000 s ALPHA Coll. Nature Physics 2011 Detection throughquenching Trapping rate Hbarsat 1S state 44

ATRAP: trapofantihydrogen Gabrielse et al. PRL 2012 Confinement for 15-1000 s High trapping rate: 5+-1 annihilations per trial 45

Ground-statehyperfinesplittingof antihydrogen 46

(Anti)hydrogen ground-state hyperfine splitting Interaction between (anti)proton and (anti)electron spin magnetic moments Between the triplet (F= 1) and singlet (F= 0) sublevels : νhfis proportional to the (anti)proton magnetic moment μp δ: higher-order QED & strong interaction corrections: ~10-3 (5 ppm2012 Gabrielse, previously 0.3%) Theoretical uncertainty on δ: ~10-6 47

AntihydrogenGS-HFS in magneticfield Hyperfine levels depend on magnetic field: Energyincreases for (F, M) = (1, 1) and (1, 0): low-field seekers(μ< 0 ) Energy decreasesfor (F, M) = (1, 1) and (0, 0): high-field seekers(μ> 0 ) B=0 48

AntihydrogenGS-HFS measurement For hydrogen: 10 12 precision (hydrogen maser) But maser not possible for antihydrogen Spectroscopy of trapped antihydrogen low precision due to strong confining field Spectroscopy of H_ beam far from largeb atomic beam method can work up to 50-100 K (for trapped H_: << 1 K) H_ can be guided with inhomogeneous magnetic field 49

ALPHA: AntihydrogenGS-HFS in a trap C Amole et al., Nature 483, 439 (2012) High magnetic field Onlyproofofprinciple ( f/f=100 MHz/29 GHz= 4 10-3 ) Start of Hbar spectroscopy 50

GS-HFS withantihydrogenbeam 51

ASACUSA Spokesperson: R. Hayano Not only antihydrogen 52

Schemeofthe measurement flip Hbar spin confine pbarsand e + ; select Hbar spin state select spin state HFS-states: de-focused LFS-states: focused B and E axially symmetric 53

Schemeofthe measurement off resonance on resonance Disappearance Mode 54

Schemeofthe experimentalset-up ASACUSA p e + 100 ev e + accumulator AD RFQD MUSASHI p trap cusp trap H_ beamline 5.3 MeV 115 kev 150 ev ε=25% 3D tracking detector p : accumulation(3 5 AD shots), compression in MUSASHI pulse extraction from MUSASHI transfer of3 10 5 tothe cusptrap guided by magnetic fields(non adiabatic transport?) e + : 22 Na source (0.6 GBq), Ne moderator, N 2 gas moderator, MRE accumulation(10 100 stacks) transfer of 3 10 7 every 10 min to the cusp 55

RadiofrequencyQuadrupoleDecelerator RFQD inverse linac RFQD 56

Antiprotonaccumulator(MUSASHI) RFQDfoilcapturecoolwithe-compresstransport tocusp RFQD+MUSASHI 5-50 more pbars than other experiments 57

experimentalset-up 58

experimentalset-up MUSASHI MUSASHI 59

experimentalset-up 60

Antihydrogenformation 61

Antihydrogenformation Hbar formation p Field Ionization of Hbar ( pbar capture) 62

Antihydrogenformation p annihilation signal First antihydrogen production in a cusp trap 63

Trackingdetector 65

Annihilationsvertices 66

Annihilationsvertices 67

Increaseantihydrogenproduction 68

Fieldionizationmeasurement 69

Antihydrogenbeam expected polarization of antihydrogen beam 70

Antihydrogenbeam Not yet used Hbar detector Field Ionization before the detector OnlyHbarswithn<43 (or n<29) reachthe detector BGO measures energy deposition by Hbar annih. coincidence: BGO AND (>1 S) 71

Energy depositionin the BGO mostly Hbars Background = pbars e - mixing 72

Antihydrogensreachingthe BGO a-c (see previous slide) IntegrationfromE th to200 MeV After detection efficiency correction(from GEANT) 25 Hbars/hour(n<43) 16 Hbars/hour(n<29) 73

Nextsteps Study and improve the beam features(hbar numbers, temperature, n-states, ) Introduce MW cavity 74

Expectations D D=10 cm, v=1 km/s 1/T=10 khz f/f=7x10 6 σ=7x10 7 Achievableresolution: -betterthan10-6 fort < 100 K -100 Hbar/s in 1S state needed (in 4 π)eventrate=1/min. 1 improvement(ramsey): Linewidth reduced by D/L Antihydrogenfountain: -trapping and laser cooling - Ramsey method with L=1m Δf ~3 Hz, Δf/f~ 2x10 9 <-- AEGIS 75

Future 2014 2017 ELENA decelerator: 5.3 MeV100 kev x 100 pbars trapping efficiencies 4 experiments can run in parallel 76

Summary Antihydrogen research: -covers many fields of physics (particle, atomic, plasma, accelerators, ) - requires modest resources (but needs time) - promises high sensitive tests of CPT symmetry - several improvements performed - recent results on production, trapping and beam formation spectroscopy era 77