The CERN Physics Programme - The (AD) & ELENA

Dániel Barna

Wigner Research Centre for Physics, Budapest, Hungary

● The CERN antiproton facilities ● Experiments, their programmes and results

The CERN Antiproton Decelerator ● Deceleration: 3.57 GeV/c → 100 MeV/c (Ekin=5.3 MeV)

● Stochastic and cooling

● 1 bunch (~107 P) / 100 s (beam steering is painfully slow...)

ELENA – The future of @ CERN ● ELENA = Extra Low ENergy Antiproton ring – under construction! ● Extension to the Antiproton Decelerator, 30.4 m circumference ● Further decelerate antiprotons to 100 keV to improve efficiency of experiments ● Allow simultaneous running of multiple experiments

The ELENA Ring

electron cooler

ELENA: electrostatic beamlines

p/H- source for commissioning and quick beamline setup

ELENA: electrostatic beamlines

p/H- source for commissioning and quick beamline setup

pin pout

The ELENA Switch

Installed and commissioned with 100 keV H- beam ELENA: electrostatic beamlines 4 bunches (1 μs) per shot: 4 experiments can run in parallel

Quick electrostatic switches distribute beam to 4 experiments running parallel ELENA: electrostatic beamlines

Static spherical deflectors where no quick switching is needed Quick switches and deflectors

FastFast deflector deflector (<1 (<1 μs) μ givings) giving 220220 mrad mrad kick kick (J. (J.Borburgh Borburgh et.al.) et.al.)

Spherical electrostatic deflector giving 33o deflection ELENA: electrostatic beamlines

Straight sections: electrostatic quadrupoles - FODO transport Quadrupole doublet + steerer unit

The antiproton physics programme at CERN

Running and planned experiments at the AD & ELENA

● ATRAP ( TRAP) H laser (to come), p & q/m ● ALPHA (Antihydrogen Laser PHysics Apparatus) H laser & mw spectroscopy, (to come) ● Asacusa (Atomic Spectroscopy And Collisions Using Slow Antiprotons) H mw spectroscopy,

p-He laser spectroscopy (mp/me),

antiproton dE/dx, σannihil in ● BASE (Baryon Antibaryon Symmetry Experiment) p magnetic moment & q/m ● AEGIS (Antihydrogen Experiment: Gravity, Interferometry, Spectroscopy) H gravity ● GBAR (Gravitational Behaviour of Antihydrogen at Rest) Future, with ELENA: H gravity ● ACE (Antiproton Cell Experiment) cancer therapy, finished Running and planned experiments at the AD & ELENA

● ATRAP (Antihydrogen TRAP) H laser spectroscopy (to come), p magnetic moment & q/m

● s ALPHA (Antihydrogen Laser PHysics Apparatus) nt H laser & mw spectroscopy, gravity e im ● Asacusa (Atomic Spectroscopy And Collisions Using Slow Antiprotons)er H mw spectroscopy, p ex p-He laser spectroscopy (m /m ), p e ed antiproton dE/dx, σ in matter s annihil ba ● - BASE (Baryon Antibaryon Symmetry Experiment) ap p magnetic moment & q/m Tr ● AEGIS (Antihydrogen Experiment: Gravity, Interferometry, Spectroscopy) H gravity ● GBAR (Gravitational Behaviour of Antihydrogen at Rest) Future, with ELENA: H gravity ● ACE (Antiproton Cell Experiment) cancer therapy, finished The antiproton physics programme

● Most experiments want to compare - antiproton properties: test CPT

● ... which works very well so far. Need to find very tiny differences. High-precision physics.

● Antiproton physics is interesting: these experiments are the highlight visit targets when LHC is running...

● ... it produces important physics results as well!

Antiproton physics is on the headlines t xperimen ALPHA e

Antiproton physics is on the headlines t xperimen ATRAP e

Antiproton physics is on the headlines ASA CUSA ex periment

! beam drogen Antihy

Antiproton physics is on the headlines ASA CUSA ex periment

Antiproton physics is on the headlines ASA CUSA ex periment

Assum ing CPT, contr antiproto ibute to t nic heliu ma he officia m resul ss ratio l value o ts f proton/ electron

ACE Antiproton Cell Experiment

Antiproton Cell Experiment

● Goal: highest localised energy deposition in the tissues, without damaging the surroundings charged particles ()

antiprotons

Antiprotons can be more efficient

Simulation Antiproton Cell Experiment

● Until they stop, they deposit about the same energy as protons

● : ~ 30 MeV strongly localised energy deposition

π π π π p n p p p n n π π π π n Nucleus recoil: to o slow, low range h p Fission Relativistic have fragments small energy deposition slow, short range Antiproton Cell Experiment

Target: cells suspended in gel Sliced after irradiation to measure survival rate

50 MeV antiproton beam

Antiproton Cell Experiment non-targeted zone: higher Targeted zone: smaller survival survival rate rate y t i l i b a b o r p l a Protons

v Antiprotons i v r u S Depth Depth

ALPHA Synthesis of antihydrogen Laser & MW spectroscopy, gravity

e+ source

Superconducting

Production and trapping of antihydrogen for laser spectroscopy 1) Capturing antiprotons

Penning-Malmberg trap (=multiring trap)

Longitudina l p (5.3 MeV)

Production and trapping of antihydrogen for laser spectroscopy 1) Capturing antiprotons 2) Cooling by in the same trap

Production and trapping of antihydrogen for laser spectroscopy

3) To capture oppositely charged in the same trap: modify the potential

antiprotons

positrons V1 V2 V3 V7

Production and trapping of antihydrogen for laser spectroscopy

4) Antihydrogen synthesis Antiprotons need to get in contact with positrons, at low velocities antiprotons

● Excite axial motion of antiprotons... positrons ● ...in an anharmonic potential (frequency is a function of amplitude) ● Use a frequency-chirped excitation (frequency is function of time) to precisely control the oscillation amplitude... ● ...and align the 'turnover' point of antiprotons (v=0) with positrons

● Autoresonant excitation (C.Amole, et.al., Phys. Plasmas 20, 043510 (2013)) Production and trapping of antihydrogen for laser spectroscopy 5) Trap antihydrogen for laser spectroscopy

The neutral antihydrogen escapes the Penning-Malmberg trap immediately.

Add a multipole magnetic field (“Ioffe-Pritchard” trap) with H minimal magnetic field at the centre.

Nature 7 The “low field seeking” spin-states of H can be trapped if initial kinetic energy < trap depth (for more than 1000 s!) (2011), 558 Alpha achievements

● H synthesized and trapped routinely (1 trapped H per attempt (20min) & 104 p), practically arbitrarily long (Nature 7 (2011), 558)

● Shining on-resonance MW onto trapped H induced spin-flip and escape from trap resonant MW on (yes-no experiment, no spectroscopy yet) (Nature 483(2012), 439) Will be improved in future

● Quickly switch off magnetic trap and observe “free fall” (annihilation position) time [s]

-65 < mH,grav / mH,inertial < 75 (95% conf.lev) Dedicated setup (vertical trap) is planned in the future

● 1s-2s laser spectroscopy is coming this summer, probably. Spectroscopy of antihydrogen

TODAY:

ALPHA: ~ 1 trapped H per attempt (104 p )

ATRAP: ~ 5 trapped H per attempt (106 p, 2 heures)

FUTURE (probably this year): laser spectroscopy of trapped antihydrogen H 1s-2s laser spectroscopy with a single ?

● H has a finite oscillation in the trap

● Overlap with the focussed laser beam?

● Need long interaction time. Cosmic background would exceed the signal over a long period (remember: there is probably just 1 H in the La trap) ser

● After a 1s --> 2s transition a second from the same laser ionizes the H

● Keep the charged-particle trap ON as well, which captures p after the

● Integrate over a long time

● Then suddenly switch off the trap and detect if there was a p ATRAP Antihydrogen synthesis and laser spectroscopy, p q/m and μ

Antihydrogen production by Cesium (ATRAP)

Cs

Cs (excited)

Antihydrogen production by Cesium (ATRAP)

e+e+

e-e-

e+e+ e+e+

e-e- e-e-

e+e+

e-e- Cs+

Antihydrogen production by Cesium (ATRAP)

e+e+ pp

e-e-

H (excited)

Possible to control H state by the laser energy Magnetic moment of antiproton: ATRAP B~5.7 Penning trap

-V Oscillation in longitudinal electric +V potential p +V

-V

Magnetic moment of antiproton: ATRAP

Penning trap + magnetic bottle

-V

+V

+V

-V

Magnetic moment of antiproton: ATRAP

Penning trap + magnetic bottle

-V Slower oscillation +V p +V

-V

Magnetic moment of antiproton: ATRAP

Penning trap + magnetic bottle

-V Faster oscillation

+V ● p Measure frequency to determine spin- state +V ● Induce spin flips via MW -V ● Determine spin-flip probability vs. MW frequency Magnetic moment of antiproton:

ATRAP p

Resonance

Line shape due to p sampling the inhomogeneous B field of the trap

J. DiSciacca, et.al., PRL 110(2013), 130801 Magnetic moment of antiproton:

ATRAP p

Precision:

μp = μp (5 ppm)

J. DiSciacca, et.al., PRL 110(2013), 130801 BASE Baryon Antibaryon Symmetry Experiment antiproton & proton: q/m & μ

Antiproton charge-to- ratio

● Measure cyclotron frequencies of a p and a H- alternatingly in the same trap

● -11 (q/m)p – (q/m)p = 1 ± 7·10

BASE - S.Ulmer, et.al., Nature 524 (2015), 196 Magnetic moment of antiproton Double-trap: BASE Try to make spin-flip via MW excitation

Magnetic bottle – detect spin-state

Magnetic moment of antiproton Double-trap: BASE Try to make spin-flip via MW excitation

Magnetic bottle – detect spin-state Today: Δμ/μ = 3 x 10-9 with a single proton

Repeat with a single antiproton! (A. Mooser, et.al.: Nature 509 (2014), 596) Asacusa experiment Antihydrogen group

MW spectroscopy of H/H (Asacusa) RFQ decelerator (100 keV) Superconducting Penning accumulator trap – capture and cooling Positron source

Synthesis trap

MW spectroscopy of H/H (Asacusa)

MW cavity – try to make a transition to a high- field-seeking state Synthesis trap. Its magnetic trap focuses the low-field- seeking states of H MW spectroscopy of H/H (Asacusa)

Sextupole filter: focuses only if no transition occured

Detector

MW cavity – try to make a transition to a high- field-seeking state Synthesis trap. Its magnetic trap focuses the low-field- seeking states of H MW spectroscopy of H/H (Asacusa) ] z ] H z [

H r o G t [

c y e t c e n d e

t u a q

e e r t f a

r With beam!

magnetic field [T] ν-ν0 [kHz] M.Diermaier,et.al., Hyperfine Interactions 233(2015), 35 TODAY: ● 80 H detected (without the MW cavity) ● Relative precision of 10-7 reached with a hydrogen beam FUTURE : MW spectroscopy of H (needs a lot of H !!) Gravity experiments

AEGIS

Antimatter & gravity - AEgIS

pp

e+e+

SiO2

Antimatter & gravity - AEgIS

e+e+

e-e-

pp

Laser e+e+ (excite the )

SiO2

Antimatter & gravity - AEgIS

e-e-

H H Stark acceleration H H H emission in 4π

e+e+

SiO2

Antimatter & gravity - AEgIS

Moiré deflectometer

The periodic pattern is displaced due to gravity

Detector: emulsion ! (Gives best spatial resolution; no time resolution is needed)

GBAR Gravitational Behaviour of Antihydrogen at Rest

Antimatter & gravity: GBAR

electron linac e+ production target

Antimatter & gravity: GBAR

e+ production target e+e+ e-e-

s) ite P exc er ( Las

Antimatter & gravity: GBAR H+ trap

● H+ trapped together with Be+

● Be+ cooled by laser

● H+ cooled by Be+ down to ~20 μK (~1 m/s)

● Ionisation by laser: H+ → H (neutral, starts falling)

● Mesure the time-of-flight

Asacusa experiment spectroscopy group

Trapping antiprotons?

● All experiments so far used Penning traps (or variants of it) to trap antiprotons and make precise measurements on it, or create antihydrogen

● Is this the only way?

An alternative way to trap antiprotons – exotic  P stops in material – replaces an electron in an atomic orbit – cascades down immediately (and annihilates) -5  Emitted radiation: X-ray. Spectrum → m (precision: 5 x 10 ) P

Antiprotonic helium – a unique  P replaces one electron: nucleus + P + electron in high Rydberg state (n~38, l~n-1)  ~3% in metastable states (lifetime: 3-4 μs, enough for experimenting)  antiproton's atomic transitions are in ] the visible range . u .

a 97% [

(laser spectroscopy, high precision) s

 -9 n o

Simple enough for 10 calculations, or better i t 3% metastable a l (Master of it: V. Korobov) i h i n n a

f o An exotic atom is a Nature-made trap, # free from man-made imperfections Time [μs] Principle of laser spectroscopy of pHe

P principal quantum number

P orbital quantum number Principle of laser spectroscopy of pHe

Why metastable? ● In high-L states, negligible overlap with the nucleus ● Electron removes degeneracy, protects from collisions ● Due to large ionization potential: Auger decay would require transitions with large Dn, which P principal would require large quantum number DL (suppressed)

P orbital quantum number Principle of laser spectroscopy of pHe

Laser-induced population transfer

Principle of laser spectroscopy of pHe

H-like ion with degenerate levels

Laser-induced population transfer

Principle of laser spectroscopy of pHe p

p

p

Collisions: Stark mixing

Laser-induced population transfer

Principle of laser spectroscopy of pHe p

p

p

Collisions: Stark mixing

Laser-induced population transfer

TIME [ns] What exactly can we learn from P-He spectroscopy?

● Measure atomic transition frequencies of antiprotonic helium: νexp

● Compare it to theoretical 3-body calculations: νth [V.I. Korobov, for example: Phys. Rev. A77 (2008) 042506]

● Interpretation:

Frequency is function of many constants: νth(mHe, q, me, mP) Use this hydrogen-like parametrization: * m ̄p 2 1 1 νn, l →n' ,l '= R c Z eff (n ,l ,n ' , l ' )( 2 − 2 ) me n n' Known to extremely high Screening by electron; use QED to precision calculate

Let νth(mP/me) ≡ νexp  mP/me – a dimensionless constant

Long history, continuously increasing precision

AD, no RFQ decelerator: high density target needed to stop p LEAR collisional shifts

Pulse-amplified CW laser, frequency comb Doppler-width @ T=10K decelerating-RFQ, pbar stops in low- density target laser linewidth

●2-photon spectroscopy (overcome Doppler-limit) ●Better cryostat at 1.5 K

Experimental layout

40-100 keV

Asacusa: laser spectroscopy of p-He

Target: helium gas, T=1.5 K

RFQ Decelerator (100 keV)

The Asacusa pHe beamline & exp.

Measured resonance profiles with 2-photon spectroscopy

P 4He (33,32)→(31,30) P 3He (35,33)→(33,31)

-1 0 1 -1 0 1 Laser frequency offset [GHz] Laser frequency offset [GHz] Fractional precision of 4 P He (36,34) → (34,32) frequency: 2.3-5 x 10-9 Hyperfine lines caused by the Precision of interaction between antiproton/electron mass S l (S ) -9 e P 3He ratio: 1.3 x 10 Agreement with proton within errorbars

-1 0 1 CODATA is using these [Nature 475 (2011) 484] Laser frequency offset [GHz] results for proton/electron mass ratio (assuming CPT) (Anti)proton-electron mass ratio

Indirect (spin-flip measurements) {

CODATA 2010

Summary

● CERN has an intensive antiproton programme ● Will continue for the coming 10-15 years with ELENA (under construction) ● Low-energy, high-precision experiments ● Measuring fundamental constants, testing symmetries ● Antiproton physics is interesting, it has produced – and is expected to produce headline news...