1. PADME: Dark photon search at the Frascati Beam-Test Facility
Paolo Valente
INFN Roma
Ferrara 13/04/15

2. Outline g’=A’=U Motivation for dark photon searches
The dark sector basic model
Recent progress on the Dark Photon searches
The Frascati linac and the beam-test facility
Positron Annihilation into Dark Matter Experiment: the PADME proposal
Beam conditions and the Target
The electromagnetic calorimeter
The dipole magnet
The spectrometer
The Vacuum chamber
Analysis technique for annihilation production
Signal selection criteria
Positron flux measurement
Limit evaluation
Experimental technique for bremsstrahlung production
Decay in e+e- pair in thin target experiment
The dump experiments
Conclusion and prospects
g’=A’=U
Paolo Valente
Ferrara 13/04/15

3. Why a secluded or dark sector?
Dark matter, in the strict sense, established since 1930 (Zwicky)
Many ideas and models, also more experimental evidence from cosmology
Current cosmological “standard” model, LCDM, requires dominant cold dark matter
No new particle, beyond the Standard Model, so far from particle physics
Problem: connect dark matter (e.g. WIMPs) to SM particles while being compatible with direct measurements:
Low elastic cross section on nuclei
Low production rates at colliders
Solution: DM not directly connected to the SM, but only through “mediator” particles
Hidden or secluded or dark sectors often present in string theories and super-symmetry
Simple model: add additional U(1)’ gauge group, but a vector boson is not the only possible mediator
The mediator could be not the lightest dark particle and thus it is not itself a DM candidate
Nuclear recoil too weak
MeV
GeV
TeV
Paolo Valente
Ferrara 13/04/15

4. Portals to secluded sector
vector
dark photon
Higgs
dark scalar
neutrino
sterile neutrino
axion
ALPs
Paolo Valente
Ferrara 13/04/15

5. The simplest dark sector model
The simplest hidden sector model just introduces one extra U(1) gauge symmetry and a corresponding gauge boson: the “dark photon" or U boson.
Two type of interactions with SM particles should be considered
As in QED, this will generate new interactions of the type:
Not all the SM particles need to be charged under this new symmetry
In the most general case qf is different in between leptons and quarks and can even be 0 for quarks. (P. Fayet, Phys. Lett. B 675, 267 (2009).)
The coupling constant and the charges can be generated effectively through the kinetic mixing between the QED and the new U(1) gauge bosons
In this case qf is just proportional to electric charge and it is equal for both quarks and leptons. e- A’ e+ A’ g
Paolo Valente
Ferrara 13/04/15

6. A’ production and decays
U boson can be produced in e+ collision on target by:
Bremsstrahlung: e+N →e+NA’
Annihilation : e+e-→ gA’
Meson decays
If no dark matter candidate lighter than the A’ boson exist:
A’→e+e-,m+m-,p+p- the so called “Visible” decays
For MA’<200 MeV A’ only decay to e+e- BR(e+e-)=1
If any dark matter c with 2Mc<MA’ exist
A’ will dominantly decay into pure dark matter and BR(l+l-) becomes small suppressed by e2
A'→cc ~ 1 so called “Invisible” decays”
Paolo Valente
Ferrara 13/04/15

7. Contribution to g-2 from dark photon
Muon g-2 SM discrepancy
About 3s discrepancy between theory and experiment (3.6s, if taking into account only e+e-hadrons)
Contribution to g-2 from dark photon A’
Paolo Valente
Ferrara 13/04/15

8. Dark sector with dark Higgs
Model assumes the existence of an elementary dark Higgs h’ boson, which spontaneously breaks the U(1) symmetry. PRD 79, (2009)
U boson can be produced together with a dark Higgs h’ through a Higgs-strahlung e+e-→Uh’
Cross section =20fb x (a/aD)(e2/10-4)(10GeV)2/s
For light h’ and U (MU,h’<2Mm) final state with 3(e+e- pair) are predicted
Background events with 6 leptons are very rare at this low energies
Due to U,h’being very narrow resonances strong kinematical constraints are available on lepton pair masses
Experimental search by BaBar and KLOE for U masses above 200 MeV
Paolo Valente
Ferrara 13/04/15

9. Experimental status U(1) + dark higgs
BaBar Phys. Rev. Lett. 108, (2012)
KLOE-2 arXiv:
Production mechanism being bremsstrahlung allows PADME to reach >100MeV A’ masses
No data available below 200 MeV in MA’
PADME can provide sensitivity in unexplored parameter region.
Paolo Valente
Ferrara 13/04/15

10. Fixed target experiments
Radiative background e-
Fixed target experiments yield higher luminosity than e+e- collisions but…
Main backgrounds:
SM Bremsstrahlung
Bethe-Heitler
Kinematics:
A’ takes nearly all the beam energy E0 (sharp peak at x≈1)
Electron takes a small energy ≈ mA’
A’ emission almost collinear to the beam: qA’=(mA’/E0)3/2
Electron going at “wide” angle: qe=(mA’/E0)1/2
A’ decay products open by q ≈ mA’/E0 e+ e- e- g
Bethe-Heitler background e- e- e+ e- e- E’ E0
Target q
qA’ e+ qe E e-

11. Dark photon experiments
Thick target (beam-dump)
Absorb all SM backgrounds
Look for visible decays
Thin target + decay of dark photon:
Decay to visible particles (e+ e-, m+ m-, …)
“Bump hunting”, looking for a peak in the invariant mass
Displaced vertices, looking for long-lived particles
Decay to invisible particles
Look for missing mass
DM particles recoil
[Meson decays]

12. Electron beam-dump experiments
Decay region
Detector
Target
Shield
Electron energy distribution due to interactions in target and shield
Decay probability of g’ after shield
ds/dx for g’ production by Bremsstrahlung

13. Limits from electron beam-dump experiments
Beam-dump experiments: looking for decay products of “rare penetrating particles” behind a stopped electron beam
SLAC E141 (1987) and E137 (1988), Fermilab E774 (1991)
Experiments re-interpreted recently in terms of dark-photon exclusion (e.g. Sarah Andreas)
E137
Lshield =179 m
Ldecay = 204m
5×109
275 GeV
2×1015
9 GeV
2×1020
20 GeV
Nobs = 0
m+m-
hadrons

14. Limits from electron beam-dump experiments
decay in dump
Lsh E0
Not enough energy E0
Ldec Ne
decay too far
rate too small
INFN CSN1 - LTS1 Workshop

15. Dark photon searches in the world
MAMI
COSY
GSI
VEPP-III
Cornell
ATLAS, LHC
SPS
SPS
NA48/2
DAFNE
BTF
PEP-II
JLAB: APEX
HPS, DarkLight
BDX
BelleII
SuperKEKB
Status: publishing, approved, proposals
Paolo Valente
Ferrara 13/04/15

16. Dark photon with thin targets
HPS JLAB
Paolo Valente
Ferrara 13/04/15

17. Dark photons in meson decays
Production (kinetic mixing)
Decay (No light dark sector)
Batell, Pospelov and Ritz PHYS. REV. D 80, (2009)
MA’<Mp0 and no lighter wrt A’ dark sector particle exists: BR(A’→e+e-)=1
Paolo Valente
Ferrara 13/04/15

18. NA48/2 dark photon limit Select p±p0D and p0Dm±n decay
Compare data and Monte Carlo
Search for unexpected peak in the Mee
No excess observed → set a limit in e2
arXiv: v1
Paolo Valente
Ferrara 13/04/15

19. Dark photon searches status
Favored parameters values explaining g-2 (green band)
A’-boson light MeV
Status of dark photon searches
Beam dump experiments (grey)
Fixed target
Peak search in BG
Mesons decays
Peaks in M(e+e-) or M(m+m-)
Indirect exclusion from ge-2 gm-2
Recent tight limit in blue filled area
arXiv: v2
Many different techniques, assumptions on dark photon interaction models
Kinetic mixing, decay to electrons, no dark sector particles
Paolo Valente
Ferrara 13/04/15

20. Status eq≠0 and A’→e+e-
g-2 muon band excluded by recent NA48/2 measurement
Paolo Valente
Ferrara 13/04/15

21. Meson decays not included the (g-2)m band is not covered any more
Status eq=0 and A’→e+e-
Meson decays not included the (g-2)m band is not covered any more
Paolo Valente
Ferrara 13/04/15

22. Status eq=0 and A’→cc decays
Removing the assumption BR(A’→e+e-=1) and introducing dark matter
Paolo Valente
Ferrara 13/04/15

23. Why dark photon invisible decays?
W. J. Marciano et al.
The invisible search technique remove any assumption except coupling to leptons
A’ increase its capability of having escaped detection so far
No data in the minimal assumptions
“If, instead, the A’ decays primarily into invisible light particles (e.g. a pair of dark matter particles with mass < mA’/2), that change would essentially negate all the bounds except those coming from anomalous magnetic moments”
arXiv: v2
W. J. Marciano et al. arXiv: v2
At present there are no MI experimental limit for the A’invisible decay
Just a never published ArXiv by Babar ‘08 with very limited sensitivity on e2 (U3SgU assumes coupling to quarks!)
Indirect limit from K+→p+nn (assumes coupling to quarks!) arXiv: v1
Paolo Valente
Ferrara 13/04/15

24. Invisible dark photon and kaons
In models assuming that the dark photon couples to SM through kinetic mixing eq≠0 K±→p±nn can be used to constrain K±→p±A’
Zd=A’ for Marciano!
Depending on how the model is build the limit can change significantly for example allowing the presence of dark Z.
Paolo Valente
Ferrara 13/04/15

25. The PADME approach
At present all experimental results rely on at least one of the following model dependent assumptions:
A’ decays to e+e- (visible decay assumption BR(A’→e+e- = 1)
A’ couples with the same strength to all fermions (eq= el) (kinetic mixing)
In the most general scenario (PADME)
A’ can decay to dark sector particles lighter than the A’ BR(A’→e+e- <<1)
Dump and meson decay experiment only limit e2BR(A’→e+e- <<1)
A’ can couple to quark with a coupling constant smaller el or even 0
Suppressed or no production at hadronic machines and in mesons decays
PADME aims to detect A’ produced in e+e- annihilation and decaying into invisible by searching for missing mass in e+e-→gA’ A’→XX
No assumption on the A’ decays products and coupling to quarks
Only minimal assumption: A’ bosons couples to leptons
PAMDE will limits the coupling of any new light particle produced in e+e- collision (scalars (Hd), vectors (A’ and Zd))
Paolo Valente
Ferrara 13/04/15

26. DAFNE complex in Frascati
DAFNE, replacing ADONE (operational until 1993), has been running as e+e- collider at 1,02 GeV since 1999, for KLOE, DEAR, FINUDA, Siddharta, and now KLOE/2 …
Synchrotron light source operational with 3 lines (X, UV, IR)
High current electron/positron linac + damping ring + test facility
Power supplies
modulators
linac
Synchrotron light
DAFNE
KLOE hall
Pumps
BTF
Cryogenics
Power supplies
Damping ring
Paolo Valente
Ferrara 13/04/15

27. LINAC parameters
Design
Operational
Electron beam final energy
800 MeV
510 MeV
Positron beam final energy
550 MeV
RF frequency
2856 MHz
Positron conversion energy
250 MeV
220 MeV
Beam pulse rep. rate
1 to 50 Hz
Beam macropulse length
10 nsec
1 to 40 nsec
Gun current
8 A
Beam spot on positron converter
1 mm
norm. Emittance
(mm. mrad)
1 (electron)
10 (positron)
< 1.5
RMS energy spread
0.5% (electron)
1.0% (positron)
electron current on positron converter
5 A
5.2 A
Max output electron current
>150 mA
350 mA
Max output positron current
36 mA
100 mA max
Trasport efficiency from capture section to linac end
90%
Accelerating structure
SLAC-type, CG, 2π/3
RF source
4 x 45 MWp SLED-ed klystrons TH2128C
The “shotgun” of the system is of course the high-current linac
Paolo Valente
Ferrara 13/04/15

28. The beam test facility BTF LINAC Main rings BTF control room 10 m
Power supplies
BTF
BTF
control room
Damping
Ring
transfer line
LINAC
10 m
transfer line
Main rings
Paolo Valente
Ferrara 13/04/15

29. DAFNE Beam Test Facility (BTF)
Longer Duty Cycle
Standard BTF duty cycle = 50*10 ns = 5x10-7 s
Already obtained upgrade 50*40ns= 20x10-7 s
Work in progress to reach 150 ns (new pulser) …
… Up to 250 ns (double phase inversion at the SLED) …
… and beyond (no SLED, or SLED detuning), in principle up to 4 ms
Energy upgrade planned in 2017.
Region from 0-22 MeV can be explored with 550 MeV e+ beam
The accessible MA’ region is limited by beam energy
e.g. MA’ up to 28 MeV with 750 positron beam
240 ns, 0.5% energy spread achieved at SLAC (same linac) for E-154 experiment
Paolo Valente
Ferrara 13/04/15

30. BTF beam summary Energy spread Dp/p ~1% Beam spot: <1 mm RMS
Divergence: 1 – 1.5 mrad
Effect of multiple scattering and Bremsstrahlung on the Beryllium exit window and in air has to be considered
Both size and divergence depend on the optics
Beam position: 0.25 mm RMS
Pulse duration: 1.5 – 40 ns
10 ns during collider operations
Measurement of the beam E spread
Beam spot size
Beam spot center
Beam E spread
Nucl. Instrum. Meth. A718 (2013) 107–109
Paolo Valente
Ferrara 13/04/15

31. The PADME experiment
e+ on target per bunch at 50 bunch/s ( e+/year)
Basic detector components:
Active 50mm diamond target
GEM based magnetic spectrometer ~1m length
Conventional 0.6T magnet
15 cm radius cylindrical crystal calorimeter with 1x1x20 cm3 crystals
1.75 m
Paolo Valente
Ferrara 13/04/15

32. The PADME experiment By C. Capoccia LNF SPAS Paolo Valente
Ferrara 13/04/15

33. The PADME diamond target
First BTF test-beam with polycrystalline diamonds:
Two 500 mm thick and 4 metal strips: 6.5 mm long and 1.5 mm pitch
300 mm thick 40 graphitized strips 3 mm long, 100 mm width, and 170 mm pitch
50 mm thick, 2×2cm2 sample for first PADME prototype
50 mm thick 5×5mm2 sample for BTF beam diagnostics with Silver Paint 1.
50 mm, silver painted,
Estimated CCD=10-20mm 2.
Main result of feasibility of 50 mm sensors already established 4. 3.
Paolo Valente
Ferrara 13/04/15

34. A possible analyzing magnet for PADME
116 cm
11 to 20 cm gap
52 cm
Paolo Valente
Ferrara 13/04/15

35. A possible analyzing magnet for PADME
Tapered poles
95 kW
42 kW
16 kW
Paolo Valente
Ferrara 13/04/15

36. PADME vacuum vessel study
Al 2219 T851 or AL6082 T6
2 mm side walls
4 mm ribs
C. Capoccia
LNF SPAS
Different possibilities under study to minimize the material thickness
Different possibilities under study to minimize the material thickness
Frascati, Servizio Vuoto
V. Lollo, S. Bini
Paolo Valente
Ferrara 13/04/15

37. PADME spectrometer
Outside
Inside
trackers
trackers
vacuum vessel
vacuum vessel
There is the possibility of having a spectrometer outside the vacuum:
Impact on the PADME-visible experiment to be understood
Paolo Valente
Ferrara 13/04/15

38. The electromagnetic calorimeter
30 cm
Cylindrical shape: radius 150 mm, depth of 200 mm
Inner hole 4 cm radius
Active volume cm3 total of 656 crystals 10x10x200 cm3
Material LSO(Ce): high LY, high r, small X0 and RM, short tdecay
Material BGO: high LY, high r, small X0 and RM, long tdecay, (free form L3?)
Expected performance:
s(E)/E =1.1%/√E ⨁ 0.4%/E ⨁1.2% superB calorimeter test at BTF [NIM A 718 (2013) 107–109]
s(q) = 3 mm/1.75 m < 2 mrad
Angular acceptance degrees
Paolo Valente
Ferrara 13/04/15

39. PADME calorimeter simulation
15 cm long LYSO crystals
20 cm long LYSO crystals
Paolo Valente
Ferrara 13/04/15

40. MC calorimeter performance
Mmiss2(MeV)
Missing mass resolution in agreement with toy MC using
s(E)/E =1.1%/√E ⨁ 0.4%/E ⨁1.2% [NIM A 718 (2013) 107–109]
Differences are ~ 10%
Resolution is the result of combination of angular resolution energy resolution and angle energy correlation due to production
Paolo Valente
Ferrara 13/04/15

41. PADME calorimeter from L3 BGO
We collected ~80 BGO crystal from L3 calorimeter. We plan to cut them in 4 pieces of 10x10x210 mm3 (up to 240 cells) Plan to test performance with 3x3mm APD and SiPM of 64 channel matrix in 2015
Paolo Valente
Ferrara 13/04/15

42. PADME Geant4 simulation
Paolo Valente
Ferrara 13/04/15

43. A PADME BG event (2000 e+)
Paolo Valente
Ferrara 13/04/15

44. Improving BG rejection
Move the front veto detector inside the beam
Thanks to the dispersion included by the dipole magnetic field, a high resolution front detector can enhance the background rejection for events with a positron emitting a soft photon
Paolo Valente
Ferrara 13/04/15

45. Search in annihilation production
Paolo Valente
Ferrara 13/04/15

46. Experimental technique
Spectrometer
ECal g
P4beam
550 MeV e+
C Target
Spectrometer
Mmiss2 A’
Search for the process: e+e- → gA’ on target e- at rest electrons
( MeV e+)/bunch beam on a 50 mm diamond target with 50 bunch/s
Collect 4x1013 e+ on target in each year of data taking period at BTF (60% eff.)
Measure in the ECal the Eg and qg angle wrt to beam direction
Compute the Mmiss2 = (P4e- + P4beam - P4g)2
P4e- =(0,0,0,me) and P4beam =(0,0,550,sqrt( me2))
Paolo Valente
Ferrara 13/04/15

47. Main background sources
Geant4 simulation accounts for:
Bremsstrahlung, 2 photon annihilation, Ionization processes, Bhabha and Moller scattering, and production ofδ-rays.
Custom treatment of e+e-→gg(g) using CalcHep generator. e- e+ g e- e+ g g e+
+1 electron
+1 g
+2 g e- e+ A’ g
Paolo Valente
Ferrara 13/04/15

48. Inclusive signal selection
Selection cuts (all decay modes)
Only one cluster in EM calo
Rejects e+e-→gg final state
5 cm < RCl < 13 cm
Improve shower containment
Cluster energy within: Emin(MA’) < ECl < 400 MeV
Removes low energy bremsstrahlung photons and piled up clusters
Positron veto using the spectrometer
Ee+< 500 MeV then (Ebeam - Ee+ - Ecl) > 50 MeV
Reject BG from bremsstrahlung identifying primary positrons
Missing mass in the region: Mmiss2A’±sMmiss2A’
Paolo Valente
Ferrara 13/04/15

49. Background estimates
e+e-→ gg(g)
e+N→e+Ng
Pile up
Data Mmiss2
BG sources are: e+e-→gg, e+e-→ggg, e+N→e+Ng, Pile up
Pile up contribution is important but rejected by the maximum cluster energy cut and MMiss2.
Veto inefficiency at high missing mass (E(e+)≃ E(e+)beam)
New Veto detector introduced to reject residual BG
New sensitivity estimate ongoing
Paolo Valente
Ferrara 13/04/15

50. PADME invisible sensitivity estimate
Based on 1x1011 fully GEANT4 simulated e+ on target events
Number of BG events is extrapolated to 4x1013 electrons on target
Using N(A’g)=s(NBG)
d enhancement factor d(MA’) = s(A’g)/s(gg) with e=1
M. Raggi, V. Kozhuharov
Adv. in HEP
Vol ID ,
Paolo Valente
Ferrara 13/04/15

51. Search in bremsstrahlung production
Paolo Valente
Ferrara 13/04/15

52. Visible search experiment
e- beam
Visible search experiment
Spectrometer
ECal e-
750 MeV e-
Target e+
Spectrometer
Search for the process: e-N → Ne-A’ →Ne-e-e+
750 MeV electron beam on a ~0.5 mm tungsten target
Measure in the spectrometer only the P4e- P4e+
Compute the MA’2 = (P4e- + P4e+)2 and decay vertex position
Search for peaks in the e+e- invariant mass
Paolo Valente
Ferrara 13/04/15

53. Indication on visible decay sensitivity
??PADME??
with e=1・10-3
Production cross section calculated with MADGraph code
Final state is more constrained by invariant mass of the e+e- pair
Indication of a limit down to e2 ~10-7 is expected at low masses
Density of tracks in the spectrometer is the crucial point to be clarified
Design of the spectrometer not yet finalized
Paolo Valente
Ferrara 13/04/15

54. Electron dumps experiments
PADME dump W ・ ~30 C ~
By S. Andreas
PADME dump MeV e-
Paolo Valente
Ferrara 13/04/15

55. High intensity Radioprotection limit:
<n> = 3.125×1010 particles/s
Typical charge to damping ring:
>1 nC/pulse for e-
nC/pulse for e+
But…
Much higher charge on positron converter
8 A (12 A) from gun cathode
A few measurements on the maximum LINAC charge, driven by beam-dump experiments requirements
Paolo Valente
Ferrara 13/04/15

56. Bunch charge vs. length E = 725 MeV ×4 increasing pulse length +30%
Decreasing grid stopping potential
×3 - ×5
Increasing gun pulse height
10 ns
10 ns
Trying to put all together: WCM readout saturated at 16 nC…

57. How many electrons on target?
Let’s compute how many eot/y* for 10 nC/pulse so we can scale easily with the charge available from the LINAC
10 nC = 10-8/1.6×10-19 = 6.25×1010
At 49 Hz (1 pulse to spectrometer line) = 3×1012 e/s
2 orders of magnitude more than present BTF authorization
Standard year = 1 y*= 120 days at 100% efficiency (107 s)
3.175×1019 eot/y*
25 nC translates in 0.8×1020 eot/y*
Considering measurements at 725 MeV, 40 ns, in the present LINAC configuration and quite conservative assumptions
Further extension of the pulse to 150 ns seems feasible with the present RF configuration, and should bring us to ≈100 nC, i.e. 3×1020 eot/y*
Where can we dump 3×1012 to 3×1013 e/s ?
Paolo Valente
Ferrara 13/04/15

58. LINAC beam dump
50 cm
30 cm
25 cm
Paolo Valente
Ferrara 13/04/15

59. LINAC beam dump
DHPTT01
A new thin vacuum chamber for DHPTT01 with a double exit
Exactly the same design of DHPTT02
A straight vacuum pipe to the inside of the cavity
Possibly, use DR pumps hall for dump experiments
DHPTT02
DR pumps hall
Paolo Valente
Ferrara 13/04/15

60. PADME dump toy Monte Carlo
Try to evaluate driving design parameters for the PADME dump
Toymc includes:
Production cross section calculated by MADgraph (thanks to A. Celentano)
Evaluate the produced number of dark photons
Scale by decay length acceptance
Scale by electron acceptance in the detector using kinematical distribution from a toy
Distribution have been compared with MADGraph for several MU
Not yet implemented in depth production of the A’
Next plot not to be considered exclusions still
Paolo Valente
Ferrara 13/04/15

61. PADME dump main parameters
Dark photon production 1 2 3 4 5
±10 cm at 1m
Electron angular acceptance
Decay length acceptance applied
Decay into the dump
e+e- out of Acc
Paolo Valente
Ferrara 13/04/15

62. Dump comparison
Zero BG hypothesis, in depth production to be refined, not yet a sensitivity plot
NA48/2
BaBar e-
DUMP
Now e-
DUMP
PADME ee
PADME mm
Real case e-
DUMP
E137
1・1020, 1.2 GeV electrons; 20 cm aperture at 50 cm from 8 cm W dump
Paolo Valente
Ferrara 13/04/15

63. BDX @ LNF A. Celentano, talk at “ What Next LNF”
Same acceptance limit at 100 MeV coming from low beam energy
aD= mc=10 MeV
Beam energy 1.2 GeV (e-)
CsI detector 60×60×225 cm3 built with crystals from dismounted BaBar ECal?
Paolo Valente
Ferrara 13/04/15

64. Energy upgrade
±10 cm at 1m
Paolo Valente
Ferrara 13/04/15

65. BTF upgrade Decays to lepton pairs Decays to invisible Energy ~√E
PADME
1013 eot
PADME
1013 eot
e+ 550 MeV
e+ 750 MeV
e+ 1 GeV
Energy
Duty cycle
Energy
Intensity
Duty cycle
PADME dump
1016 eot
Energy
Intensity
Paolo Valente
Ferrara 13/04/15

66. 15 m

67. Add 4 sections + 2 SLED-ed klystrons
+320 MeV:
Reach:
1070 MeV electrons
870 MeV positrons
Paolo Valente
Ferrara 13/04/15

68. Add 4 sections + 4 SLED-ed klystrons
+180 MeV:
+320 MeV:
Reach:
1250 MeV electrons
1050 MeV positrons
Add two more SLED-ed klystrons and split power only in two sections instead of four
Paolo Valente
Ferrara 13/04/15

69. PADME project plans
Project has been presented as a “What Next” Project in INFN CSN1
The project has received positive comments form CSN1 referees
Proposal for R&D financing will be discussed in the next CSN1 meeting
Proto collaboration formed including
LNF, Rome1, Lecce and Sofia university
6 weeks test beam time asked at DAFNE BTF in 2015
Study the prototype of BGO calorimeter solution (L3 crystals)
Test diamond target prototypes
Study the maximum beam current per bunch and beam spot size
Optimize beam characteristics for PADME operation bunch length, number of particle per bunch, background, beam positioning stability
Interesting synergy with BDX project identified (BDX at LNF?)
Many item still to be covered! Search for more collaborators started
Paolo Valente
Ferrara 13/04/15

70. PADME kick-off meeting
PADME website
Paolo Valente
Ferrara 13/04/15

71. Outlook and plans
An experiment running at DAFNE BTF sensitive to both A’→invisible and A’→e+e- decays has been proposed to INFN CSN1
Exclusion limit in e2 down to 1-2・10-6 can be achieved in invisible decays with the present BTF beam parameters in the region MA’ MeV
M. Raggi and V. Kozhuharov, Advances in High Energy Physics Vol ID ,
Possible accessible regions for a bremsstrahlung produced A’→e+e- were identified to reach ~100MeV
Detailed study of the sensitivity in this channel are ongoing
Beam dump experiment searching for both visible and invisible Dark photon decays are also possible.
In all the cases an energy upgrade of the Linac is a plus
Paolo Valente
Ferrara 13/04/15

72. “The hardest thing of all is to find a black cat in a dark room,
especially if there is no cat”
Confucius
Paolo Valente
Ferrara 13/04/15