1. The Frascati group activity in testing SiPM related to
the AMADEUS experiment
LNF-INFN: Catalina Curceanu, Antonio Romero Vidal
Alessandro Scordo, Oton Vazquez Doce
G. Corradi, D. Tagnani - electronics
C. Capoccia - mechanics
&
IFIN-HH: M. Bragadireanu
A. Tudorache, V. Tudorache

2. Summary The Amadeus experiment: a brief introduction
Trigger system requirements
Experimental setup
SiPM characterization:
Dark count spectra
Gain and width behaviour
Beta source spectra
Temperature dependence
MonteCarlo simulations; what are we expecting?
Preliminary results of tests in Dafne
Future perspective and conclusions

3. Antikaonic Matter At DAFNE: an Experiment Unraveling Spectroscopy
AMADEUS
Antikaonic Matter At DAFNE: an Experiment Unraveling Spectroscopy

4. Study of deeply bound kaonic
Letter of Intent
Study of deeply bound kaonic
nuclear states at DANE2
AMADEUS Collaboration
111 scientists from 33 Institutes of 13 Countries
signed the Letter of Intent
March 2006, reviewed 2007, Zagreb; presently – signed Agreement with KLOE

5. K- + 4He -> n + (K-ppn) n ~ 510 MeV/c
deeply bound kaonic nuclear states
K- + 4He -> n + (K-ppn) n ~ 510 MeV/c
K- + 4He -> p + (K-pnn) p ~ 550 MeV/c 5

6. The scientific case of the so-called “deeply bound kaonic nuclear states” is hotter than ever, both in the theoretical (intensive debate) and experimental sectors.
What emerges is the strong need for a complete experimental study of the scientific case, i.e. a clear and clean experiment (so without the need to make hypothesis on involved physics processes), measuring kaonic clusters both in formation and in the decay processes.
AMADEUS’s main aim is to perform the first full acceptance, high precision measurement of DBKNS both in formation and in the decay processes, by implementing the KLOE detector with an inner AMADEUS-dedicated setup, containing a cryogenic target and a trigger system (and an inner tracker in a second phase),
Either situations: EXISTENCE or NON-EXISTENCE of the deeply bound kaonic nuclear clusters will have strong impact in kaon-nucleon/nuclei physics!!!

7. Experimental programme AMADEUS phase-1 (2)
Low-energy charged kaon cross sections on Helium(3 and 4), for K- momentum lower than 100 MeV/c (missing today);
The K- nuclear interactions in Helium reactions (poorly known – based on one paper from 1970 …)
Properties of L(1116) and charged S – for example decays in channels with neutrino -> astrophysics implications (cooling of compact stars)
Resonance states as the elusive-in-nature but so important L(1405) or the S(1385) could be better understood with high statistics; their behaviour in the nuclear medium can be studied too.
Excellent feasibility test – Oton Vazquez Doce (KLOE data)

8. The experimental setup of AMADEUS
Full acceptance and high precision measurements will be made by implementing the KLOE detector with an inner
AMADEUS setup
The AMADEUS setup will be implemented in the 50 cm. gap in KLOE DC around the beam pipe
Target: A gaseous He target for a first phase of study
Trigger: 1/2 layers of ScFi surrounding the interaction point
Inner tracker: eventually, a first tracking stage before the DC

9. AMADEUS @ KLOE, phase-1 Low-mass cryogenic gas target cell: T = 10 K
P = 1.0 bar
Rin = 5 cm
Rout = 15 cm
L = 20 cm
Kaon trigger:
two layers of
scint. fibers,
stereo angel = 30°
readout on
both sides
with SiPM

10. Trigger system
Cilindrical layer of scintillating fibers surrounding the beam pipe to trigger K+/K- in opposite directions
•Single or double layer
•Readout to be done by SiPM (Silicon Photo-Multipliers)
In case of double layer: possibility of perform tracking as well:
X-Y measurement with high granularity layers

11. Trigger System (Scintillating fibers read with SiPM)
Hamamatsu and Photonique Prototypes at LNF SMI and Russian SiPM at ITEP

12. Trigger System – LNF undergoing work (Scintillating fibers read with SiPM)

13. April 2008

14. Characterizing SiPM : HAMAMATSU S10362-11-050U
Experimental setup (we did tests on Photonique as well)
Pre-Amplifiers (X 100)‏
5 Channles HV
power supply
(stability better than
10 mV)‏
Scintillating fibers
Bicron BCF-10 (blue)‏
SiPM (HAMAMATSU U50) (400 pixels)‏
Operating voltage ~70V
Sr90 beta source (37 MBq)‏

15. Characterizing SiPM: Dark Count
Setting a threshold to 0.5 or 1.5
photoelectrons, using a scaler module
dark count rates have been evaluated

16. Characterizing SiPM: Dark Count
Detectors were cooled down in order to study
their behaviour with temperature variations.
A scan of the 1 p.e peak rate is reported
Cooling
system
Peltier cell
Dark count 1 p.e signal is reduced by a factor 20!
If high number of p.e are expected no cooling is needed

17. reading scintillating fibers
Characterizing SiPM:
reading scintillating fibers
A scintillating fiber is activated
by a beta Sr90 source
Both ends are coupled to detectors;
one is used as trigger
Setting the threshold for the SiPM used as trigger,
most part of dark count is eliminated.
In this way spectra due only to the source can be
observed

18. reading scintillating fibers
Characterizing SiPM:
reading scintillating fibers
A scaler module was used in order to obtain rates for each peak.
Studying rates with and without the beta source, it turned out that starting from the 4th p.e. Peak, dark count contribute is negligible
This means that non cooling is needed in this case!!!!

19. reading scintillating fibers
Characterizing SiPM:
reading scintillating fibers
Source cut at 5 p.e.
Source cut at 11 p.e.
Peak with most
counts: 5 p.e. (15%)
Peak with most
counts: 7-8 p.e. (11%)
Source cut at 8 p.e.
Peak with most
counts: 6 p.e. (12%)
Black spectra are the trigger-used SiPMs
Red spectra are the signal outputs
Cutting below 5 p.e. Dark count starts to be
predominant; so it seems that the beta source
leads to a 4-5 p.e. peak

20. reading scintillating fibers
Characterizing SiPM:
reading scintillating fibers
Starting from beta source spectra, peak position and width
can be studied
Adjusting the applied voltage, also the behaviour of
the gain with the Vbias can be obtained

21. Montecarlo simulations: what are we expecting?
Some geant3 simulations were done in order to understand how many p.e. should be left
by Kaons in DAΦNE
First, a simulation af a fiber+Sr90 source
was done, in order to compare it with
experimental data
Setup consists of a Bicron BCF-10
scintillating fiber, with a Sr90 source put at
a distance of 3 cm. All the solid angle of the fiber
is taken in account
Initial momentum
of electrons
Mean ~ 150 KeV
Momentum
spectrum
of Sr90

22. Montecarlo simulations: what are we expecting?
Comparing with experimental data:
Mean energy lost ~ 150 KeV photons (8000 ph/MeV)
Nominal trapping efficiency ~ 4% photons
Attenuation length ~ 2.2 m (1/e) photons (30 cm)
Q.D.E. ~ 50 % photons
Reading 1 size photons
Another important feature wich has to be taken in account is the coupling efficiency
Between fibers and SiPMs (grease, angle, etc)
This factor is not easily defined so it has to be understood comparing simulations with
Experimental data
In this way we obtain εcoupling ~ 50%

23. Montecarlo simulations: what are we expecting?Y
K- track
Beam Pipe
300 μm Alluminium
R=2.95 cm X
376 fibers
Double cladding
~ 3% of r
r=0.5mm
Setup consists in 2 layers of 70 cm scintillating fibers
BCF-10 multicladding.
Beam Pipe is an alluminium tube with radius r=2.95 cm
and 300 μm thickness.

24. Montecarlo simulations: what are we expecting?
Momentum distribution
taken from
Kloe MC
BCF-10
1mm diameter
Totally, 18.64% of
Kaons are stopped in
the whole setup
(MeV)
7.4% of Kaons are stopped in the first layer
92.6% of exiting Kaons enter in the second layer
12.2% of these Kaons are stopped in the second layer
In each layer energy lost by Kaons is ~ 2 MeV
This means a factor 13 more than Sr90 e- wich becomes a factor 10 including attenuation length for 70 cm
So we expect a number of p.e. wich is ~ 100
(50 including εcoupling)
(MeV)

25. Montecarlo simulations: what are we expecting?
BCF-10
0.5 mm diameter
Totally, 7,8% of
Kaons are stopped in
the whole setup
(MeV)
2.2% of Kaons are stopped in the first layer
97.8% of exiting Kaons enter in the second layer
5.7% of these Kaons are stopped in the second layer
(MeV)
Less Kaons stopped!
More Kaons passing through 2 layer!
Less p.e. signal!
746 fibers (instead of 346)!
→1492 SiPMs and readout
(instead of 692)
So wich fibers?
In each layer energy lost by Kaons is ~ 1 MeV
This means a factor 6 more than Sr90 e- wich becomes a factor 5 including attenuation length for 70 cm
So we expect a number of p.e. wich is ~ 50
(25 including εcoupling)

26. Preliminary tests in DAФNE
22-24 January 2009

27. Preliminary test in DAФNE
Dark count + M.I.P. (e-)
Mean ~ ch 160
Peak around ch 1600
~ X 10 as expected
Kaons?
Triggered with
the opposite side
SiPM (> 5p.e)

28. Conclusions… …and future plans
We performed accurate tests on Hamamatsu S U
Conclusions…
Hamamatsu SiPMs S U seem very suitable for our intents
Dark count is negligible when looking at signals of more than 4 p.e.
NO cooling is needed for AMADEUS trigger
…and future plans
Time resolution studies are planned in order to understand the trigger efficiency (MIPs, etc.)
Further simulations will be performed including Magnetic Field, Helium target, Kapton cell
and all other particles coming from e+-e- collisions
More tests in Daϕne with scintillating fibers activated by Kaons (more statistic)
Dedicated Monte Carlo simulations – to be continued
Electronics, power supplies mechanics

29. Collaborations with: ITEP Moscow Zagreb Univ. Perugia (Ambrosini)
Hamamatsu SiPMs S U seem very suitable for our intents
Dark count is negligible when looking at signals of more than 4 p.e.
Collaborations with:
ITEP Moscow
Zagreb Univ.
Perugia (Ambrosini)
NO cooling is needed for AMADEUS trigger
…and future plans

30. AMADEUS global strategy:
AMADEUS phase-1: start in 2011 (after KLOE2 step0), study di- and tri – baryon kaonic nuclei and low-energy kaon-nucleon/nuclei interactions
AMADEUS phase-2: after 2012, higher integrated luminosity, refined study of di- tri-baryon kaonic nuclei; extend to other nuclei (spectroscopy of kaonic nuclei along the periodic table…)