Zeudi Mazzotta Supervisor Fabrizio Castelli 1 OUTLINE The

Zeudi Mazzotta Supervisor: Fabrizio Castelli 1

OUTLINE Ø The AEg. IS experiment Ø The role of the Positronium in the AEg. IS experiment Ø Positronium Laser excitation and its detection 17/11/2014 First Year Workshop 2

The physics behind the AEg. IS experiment 17/11/2014 First Year Workshop 3

The weak equivalence principle (WEP) All matter bodies at the same spacetime point in a given matter gravitational field will undergo the same acceleration 17/11/2014 First Year Workshop All antimatter bodies at the same spacetime point in a given antimatter gravitational field will undergo the same acceleration The physics behind the AEg. IS experiment 4

The weak equivalence principle (WEP) All matter bodies at. Will theall same antimatter bodies All antimatter at bodies at the spacetime point in the a given same spacetime same point spacetime in a point in a given matter gravitational given field matter will gravitational antimatter field gravitational field undergo the samewill undergo the same acceleration? acceleration 17/11/2014 First Year Workshop The physics behind the AEg. IS experiment 5

The AEg. IS experiment 17/11/2014 First Year Workshop 6

The main goal of AEg. IS Neutral antimatter: Antihydrogen ? 17/11/2014 First Year Workshop The AEg. IS experiment 7

Antihydrogen production AEg. IS strategy Charge exchange with Positronium PROMISING TECHNIQUE Antiprotons and positrons Recombinations and • Control of the antihydrogen quantum state • Cold antihydrogen atoms (vantihydrogen ~ vantiproton) • Advantages in the cross section (see later) Usual strategy: ATRAP, APLHA and ASACUSA experiments • The second seems to be the dominant process (highly exicited antihydrogen) • Antihydrogen atoms warmer than trapped antiprotons (Hbar production when vantiproton ~ vpositron) • Low cross section 17/11/2014 First Year Workshop The AEg. IS experiment 8

The Positronium atom Ps n-level energy: para-Ps g Singlet state Mean life 0, 125 ns 2 g annihilation g orto-Ps Triplet state Mean life 142 ns 3 g annihilation g g g Energies < 511 ke. V g Energies = 511 ke. V 17/11/2014 First Year Workshop g The AEg. IS experiment 9

AEg. IS in short Antiprotons from CERN AD (Antiproton Decelerator) e+ p- p- e+ beam 17/11/2014 First Year Workshop The AEg. IS experiment 10

AEg. IS in short antiprotons cooling (~1 K) and trapping e+ accumulator p- e+ e+ pulse dumping and acceleration 17/11/2014 First Year Workshop The AEg. IS experiment 5 Tesla magnet 11

AEg. IS in short Trapped&cooled antiprotons 1 Tesla magnet e+ pulse implantation and Positronium formation 17/11/2014 First Year Workshop The AEg. IS experiment 12

AEg. IS in short Ps and p- overlap region: Charge exchange reaction takes place! 1 Tesla magnet 17/11/2014 First Year Workshop The AEg. IS experiment 13

AEg. IS in short Antihydrogen accelerated beam 1 Tesla magnet 17/11/2014 First Year Workshop The AEg. IS experiment 14

AEg. IS in short Moirè deflectometer 17/11/2014 First Year Workshop The AEg. IS experiment 15

The role of the Positronium in the AEg. IS experiment 17/11/2014 First Year Workshop The role of the Positronium in the AEg. IS experiment

The Positronium creation Positronium is created in the material bulk A bunched positron beam is sent toward a porous «target» able to convert positrons into Positronium. Silica or aerogel target Positron pulse Pores diameter ~10 nm A fraction of the Ps exiting the target is thermalized into the target pores 17/11/2014 First Year Workshop Positronium cloud The role of the Positronium in the AEg. IS experiment 17

The role of the Positronium in the AEg. IS experiment Ps is needed to create Antihydrogen in the Charge exchange reaction Required Ps excitation to Rydberg levels (n=15… 24) !!! 17/11/2014 First Year Workshop Ps area The cross section of this reaction increases with the Ps principal quantum number: The role of the Positronium in the AEg. IS experiment 18

Positronium laser excitation and its detection 17/11/2014 First Year Workshop 19

AEg. IS Ps Rydberg laser excitation strategy Continuum 0, 75 e. V ~1670 nm High n n=3 6, 05 e. V 205 nm We have to test if the laser excitation works! Use of an external test chamber, called BREADBOX n=1 17/11/2014 First Year Workshop Positronium Laser excitation and its detection 20

n=3 excitation detection strategies 1. Changes in the g-rays time distribution 2. Detection of 1312 nm photons (spontaneously emitted in the n=3 ->n=2 de-excitation branch) 3. Ps laser ionization and charges collection 17/11/2014 First Year Workshop Positronium Laser excitation and its detection 21

1. Detecting Ps n=3 laser excitation By measuring changes in the g-rays time distribution 17/11/2014 First Year Workshop Positronium Laser excitation and its detection

1. Detection of Ps annihilations into gamma rays time distribution orto-Ps para-Ps n=3 UV laser Spontaneous emission: about 10 ns n=1 Singlet Only 0. 124 ns to decay into 2 g-rays g g 17/11/2014 First Year Workshop Singlet-triplet mixing due to the presence of a weak magnetic field (~200 G) that mixes levels with the same m Triplet 142 ns to decay into 3 g-rays Observation of enhanced 2 g rays annihilation rate at the time of laser on Positronium Laser excitation and its detection 23

My Montecarlo simulation c++ & ROOT First simulation on Ps formation, excitation and TOF detection 3 D Histogram: Bread. Box walls picture in the simulation Target Detectors 17/11/2014 First Year Workshop Positronium Laser excitation and its detection 24

My Montecarlo simulation c++ & ROOT First simulation on Ps formation, excitation and TOF detection In each annihilation point we have g-rays generation! 3 D Histogram: Ps annihilation points 17/11/2014 First Year Workshop Positronium Laser excitation and its detection 25

My Montecarlo simulation c++ & ROOT First simulation on Ps formation, excitation and TOF detection In each annihilation point we have g-rays generation! 3 D Histogram: g-rays intersections with the detectors 17/11/2014 First Year Workshop Positronium Laser excitation and its detection 26

My Montecarlo simulation c++ & ROOT First simulation on Ps formation, excitation and TOF detection Elements taken into account Chamber geometry • • • Positronium physics Mean lives Maxwell-Boltzmann velocities distributions Decaying times Annihilation behaviours Gamma-rays energies generation 17/11/2014 First Year Workshop • • • Detectors physics Efficiency Time resolution Energy resolution Positronium Laser excitation and its detection 27

1. Detection of Ps annihilations into gamma rays time 17/11/2014 First Year Workshop Positronium Laser excitation and its detection 28

1. Detection of Ps annihilations into gamma rays time Increase of the «fast decaying» population and relative decrease of the «slower» counterpart 17/11/2014 First Year Workshop Positronium Laser excitation and its detection 29

2. Detecting Ps n = 3 laser excitation By measuring the spontaneous emission 17/11/2014 First Year Workshop 3 ->2 radiation Positronium Laser excitation and its detection

2. Detection of 1312 nm photons De-excitation Excitation n=3 15% 1312 n radia m tion n=2 85% 6, 05 e. V 205 nm n=1 17/11/2014 First Year Workshop The goal of this strategy is to detect the radiation emitted from this transition Positronium Laser excitation and its detection 31

2. Detection of 1312 nm photons We chose to use an In. Ga. As Avalanche Photodiode Detector (APD) IMAGING LENS in a Geiger configuration for single photon detection. In. Ga. As detector Transport + Focusing Imaging Excited Ps cloud Multimode fiber core 1312 nm radiation 17/11/2014 First Year Workshop Positronium Laser excitation and its detection 32

2. Detection of 1312 nm photons I estimated that, in order to have 1 count out of 10 e+ shots, we should deliver into the detector more than the 0, 024% of the emitted radiation Example of multimode beam Main challenge MULTIMODE BEAM focusing onto the 25 mm DIAMETER In. Ga. As active surface: Theoretical and experimental studies! w=4 mm (The active surface is so much little to reduce the dark counts rate) 17/11/2014 First Year Workshop Positronium Laser excitation and its detection 33

2. Detection of 1312 nm photons We have been able to plan an optical setup that, for every shot, gives us a 11% probability 0, 75% probability signal count dark count IMPORTANT Work in progress: Several improvement can be done!!! 17/11/2014 First Year Workshop Positronium Laser excitation and its detection 34

3. Detecting Ps n = 3 laser excitation By detecting the Ps laser ionization 17/11/2014 First Year Workshop Positronium Laser excitation and its detection

3. Ps ionization BREADBOX SETUP i 10 V/cm electric field e- Channel Plate and/or channeltron 5 ns 29 ns e+ E xy-plane electrode Porous target secondary electrons e+ emission at the time of e+ arriving on n=3 excitation the target detection x-axis Laser UV Ionizing laser y-axis electrode t 17/11/2014 First Year Workshop Positronium Laser excitation and its detection 36

3. Ps laser ionization By sending a 1064 nm laser pulse simultaneous to the exciting one (205 nm) we can ionize a fraction of the n=3 excited Ps Populations E 1064=10 m. J n=1 Ionized Ps n=3 n=2 Without 1064 nm pulse 17/11/2014 First Year Workshop n=2 Time(ns) With 1064 pulse Positronium Laser excitation and its detection Time(ns) 37

3. Ps ionization BREADBOX SETUP i 10 V/cm electric field e- Channel Plate and/or channeltron 5 ns 29 ns t 17/11/2014 First Year Workshop e+ E electrode xy-plane electrode Porous target secondary electrons e+ emission at the time of e+ arriving on n=3 excitation the target detection x-axis Laser UV Ionizing laser y-axis Laser IR: Rydberg excitation With a resonant IR: Rydberg excitation detection Positronium Laser excitation and its detection 38

The work goes on! - Improve my simulation with more and more physics. - Simulate the laser ionization. - Study more in depth the detection of the laser Ps excitation and find the best way to perform it. - Carry on my work at CERN, in Geneva, where AEg. IS apparatus and Bread. Box are placed. 17/11/2014 First Year Workshop 39

Thank you for your attention Some of my AEg. IS adventure mates inside the AEg. IS experimental zone

2. Detection of 1312 nm photons I estimated that, in order to have 1 count out of 10 e+ shots, we should deliver into the detector more than the 0, 024% of the emitted radiation Example of multimode beam w=4 mm 17/11/2014 First Year Workshop Positronium Laser excitation and its detection 41

The Positronium termalization PRL 104, 243401 (2010), Sebastiano Mariazzi, Paolo Bettotti, and Roberto S. Brusa, “Positronium Cooling and Emission in Vacuum from Nanochannels at Cryogenic Temperature” A fraction of the Ps exiting the target is thermalized into the target pores 17/11/2014 First Year Workshop The role of the Positronium in the AEg. IS experiment 42