1. Luminosity measurement at DAFNE
M. Boscolo, F. Bossi, B. Buonomo, G. Mazzitelli,
F. Murtas, P. Raimondi, G. Sensolini
INFN LNF
M. Schioppa
INFN Cosenza
Paolo Valente
INFN Roma
P. Branchini
INFN Roma Tre
N. Arnaud, D. Breton, A. Stocchi,
A. Variola, B. Viaud LAL, Université Paris-Sud
P. Valente – SuperB Workshop – 2nd June 2008

2. Machine luminosity monitors and IP diagnostics tool
Use different detectors to observe different reactions:
e+e-  e+e-g (8.5·10-26 cm-2s-1 for E>100MeV, 95% 1.7mrad)
e+e-  e+e-gg (6.6·10-29 cm-2s-1 for E>100MeV, 15% 1.7mrad)
e+e-  e+e- Bhabha scattering, more clean process
450 Hz, 18o< q cm-2 s-1
e+e-  F  K+K- About 25 expected in the SIDDHARTA experiment monitor at ~90o
Radiative Bhabha
 High rate  fast
Low angle
High background
Bhabha
Good rate
Clean process
Steep q dependence
Back-to-back trigger
Sensitive to boost
P. Valente – SuperB Workshop – 2nd June 2008

3. P. Valente – SuperB Workshop – 2nd June 2008
February 2007
P. Valente – SuperB Workshop – 2nd June 2008

4. Layout and Luminosity Monitors
SIDDHARTA
May 2007
K monitor
Bhabha calorimeter
 monitor
GEM
Bhabha Monitor
P. Valente – SuperB Workshop – 2nd June 2008

5. P. Valente – SuperB Workshop – 2nd June 2008
Gamma monitor
Detect 1.7 mrad photons of radiative Bhabha’s
Need to be very close to beam-pipe
Compact detector [small Moliere radius and X0]
High rate
P. Valente – SuperB Workshop – 2nd June 2008

6. P. Valente – SuperB Workshop – 2nd June 2008
The gamma monitor
2 calorimeters PbWO4 crystals, 13 X0 total depth
Readout by Hamamatsu R7600
High-statistics, very fast counter, main tool for luminosity optimization…
…but affected by background [not for absolute luminosity measurement]
P. Valente – SuperB Workshop – 2nd June 2008

7. P. Valente – SuperB Workshop – 2nd June 2008
Kaon Monitor
PM: Hamamatsu R4998
Scintillators: BC420
Dimensions: 200 x 50 x 2.0 mm
Triple-GEM
tracker
Triple-GEM
tracker
P. Valente – SuperB Workshop – 2nd June 2008

8. P. Valente – SuperB Workshop – 2nd June 2008
Kaon monitor
mips K
mips K
mips K K
mips
mips
mips
Courtesy
SIDDHARTA collaboration
Threshold
P. Valente – SuperB Workshop – 2nd June 2008

9. P. Valente – SuperB Workshop – 2nd June 2008
Triple-GEM trackers
pads
induction gap
GEM 3
GEM 2
GEM 1
Cathode
Final luminometers with Carioca FEE
P. Valente – SuperB Workshop – 2nd June 2008

10. Bhabha calorimeter design
Longitudinal segmentation has been optimized keeping in mind that the total available depth is only the length of the quadrupole  20 cm
11 absorber plates + 12 samplings:
8×0.5 cm + 3×1 cm lead  12.5 X0 should ensure sufficient shower containment
12×1 cm scintillator
2:1 active:passive ratio should ensure 15%/E(GeV) resolution
Lateral segmentation dictated by the need of keeping a reasonable number of channels and to have some degree of freedom in defining the acceptance
We decided to equip only 10 out of 12 sectors, keeping out the f=0º-180º plane, since we expect larger backgrounds from there
P. Valente – SuperB Workshop – 2nd June 2008

11. P. Valente – SuperB Workshop – 2nd June 2008
Tiles and WLS fibers
“Classical” tile sampling calorimeter, lead/scintillator
Scintillator tiles light read by WLS fibers
Wavelength-shifting fibers [Bicron BCF-92] collecting scintillation light [and shifting from blue to green]
Groove designed for optimal matching with 1.0 mm fibers
[2 mm depth, 1.1 mm diameter]
Each tile wrapped with Dupont TyvekTM sheet to improve light collection
12×3 fibers of one sector fed into a PMT
P. Valente – SuperB Workshop – 2nd June 2008

12. CaloLumi construction
December ‘07 – January ‘08
P. Valente – SuperB Workshop – 2nd June 2008

13. CaloLumi installation
7 February 2008
P. Valente – SuperB Workshop – 2nd June 2008

14. P. Valente – SuperB Workshop – 2nd June 2008
DAQ
KLOE SDS boards used to split, discriminate, and sum the signal to assert a trigger.
A small number of NIM modules are necessary to trigger the DAQ.
We have in the same crate KLOE calorimeter TDC and ADC boards as well as chamber TDC (1ns) read with AUX-bus custom architecture
DAQ software is also KLOE based, running on Motorola CPU MVME6100
Negligible dead-time up to tens of kHz rate
P. Valente – SuperB Workshop – 2nd June 2008

15. P. Valente – SuperB Workshop – 2nd June 2008
Trigger e+ 3 IP 1 e- 1 OR 2 3 T1 S
trg 2
threshold
P. Valente – SuperB Workshop – 2nd June 2008

16. P. Valente – SuperB Workshop – 2nd June 2008
Calorimeter response
All events
triggering
events
adc12
adc11
adc13
adc10
adc14
adc9
adc5
adc8
Energy sum
adc6
adc7
P. Valente – SuperB Workshop – 2nd June 2008

17. P. Valente – SuperB Workshop – 2nd June 2008
Energy resolution
Measured resolution with Bhabha events: 17.5% at 510 MeV
[12.4%/E(GeV)]
Very similar results in our BTF beam-test
P. Valente – SuperB Workshop – 2nd June 2008

18. P. Valente – SuperB Workshop – 2nd June 2008
Background
We can have energy deposits over threshold in another module, in addition to the couple of triggering modules: this gives us the “triples”
We expect a similar level of events with no Bhabha, but with two “spurious” deposits, giving a fake coincidence
P. Valente – SuperB Workshop – 2nd June 2008

19. P. Valente – SuperB Workshop – 2nd June 2008
Background
Bhabha peak
Si=0,…,4 (ADCi – <PED>i)
Indeed not all the triggering events look like Bhabha events…
…but it seems difficult to reject effectively background introducing a cut on energy
Additional difficulties:
dependence on sector calibration
dependence on threshold
background
P. Valente – SuperB Workshop – 2nd June 2008

20. P. Valente – SuperB Workshop – 2nd June 2008
Background topology
Cross check looking at runs with only 1 beam
run 1392, e- 350 mA, 100 bunch
run 1394, e+ 290 mA, 100 bunch
P. Valente – SuperB Workshop – 2nd June 2008

21. Background subtraction
P. Valente – SuperB Workshop – 2nd June 2008

22. P. Valente – SuperB Workshop – 2nd June 2008
Online filter  -
Use side-band to estimate background contribution under peak
P. Valente – SuperB Workshop – 2nd June 2008

23. P. Valente – SuperB Workshop – 2nd June 2008
Online filter
Since April 21st, 2008
During injections T1FREE is jumping up…
… while T2FARM can go down due to injection veto in DAQ
P. Valente – SuperB Workshop – 2nd June 2008

24. P. Valente – SuperB Workshop – 2nd June 2008
Online filter
Background contribution is – quite obviously – lower at lower currents
Smoothing due to statistical fluctuations
1000 events integrated by T2FARM
Averaged in 15 seconds [update of DAFNE control system]
P. Valente – SuperB Workshop – 2nd June 2008

25. P. Valente – SuperB Workshop – 2nd June 2008
Online filter
Good e+ injection
Bad e+ injections
P. Valente – SuperB Workshop – 2nd June 2008

26. P. Valente – SuperB Workshop – 2nd June 2008
Out-of-time events
We have assumed that in-time events are true Bhabha’s, while out-of-time coincidences, belonging to the “wide” distribution in Dt, are due to spurious events
In order to validate this hypothesis, we put the beam out of collision [by shifting the RF phase of 180 degrees]
in collision
out of collision
P. Valente – SuperB Workshop – 2nd June 2008

27. P. Valente – SuperB Workshop – 2nd June 2008
Background
out of collision
P. Valente – SuperB Workshop – 2nd June 2008

28. P. Valente – SuperB Workshop – 2nd June 2008
Threshold studies
all events
triggering
Still working on data/Monte Carlo comparison…
triggering/all
P. Valente – SuperB Workshop – 2nd June 2008

29. P. Valente – SuperB Workshop – 2nd June 2008
Simulation
All 3 monitors are simulated with GEANT3 and BHWIDE generator
Touschek background generator is also included
Sources
No tracker σsyst
GEM tracker
σsyst
Calo alignment ± 2mm 4% 2%
Soyuz alignment ± 2mm 8% 6%
SIDDHARTA Exp. 0%
Energy Th. ± 60MeV 5% 1%
BKG Accidentals 3%
BKG γγ
0.1%
Total (Σquad)
11% 7%
main sources of systematic errors
P. Valente – SuperB Workshop – 2nd June 2008

30. P. Valente – SuperB Workshop – 2nd June 2008
Effect of spot size y by z
vs x (transverse)
vs z (longitudinal)
Latest results from Monte Carlo simulations:
+15% with respect with online luminosity, due to finite spot size
P. Valente – SuperB Workshop – 2nd June 2008

31. P. Valente – SuperB Workshop – 2nd June 2008
Soyuz
q>18º
P. Valente – SuperB Workshop – 2nd June 2008

32. P. Valente – SuperB Workshop – 2nd June 2008
Soyuz
~200 MeV
16º
15º
12º
without
16º
15º
12º
with
P. Valente – SuperB Workshop – 2nd June 2008

33. P. Valente – SuperB Workshop – 2nd June 2008
Sputnik
Only Soyuz
P. Valente – SuperB Workshop – 2nd June 2008

34. P. Valente – SuperB Workshop – 2nd June 2008
Sputnik
Since May 29th, 2008
Sputnik
P. Valente – SuperB Workshop – 2nd June 2008

35. P. Valente – SuperB Workshop – 2nd June 2008
Sputnik
q>22º
Approximately a factor 2 in acceptance due to Sputnik limitation of minimum q angle
Monte Carlo evaluation under way…
Slightly less sensitive to backgrounds
P. Valente – SuperB Workshop – 2nd June 2008

36. P. Valente – SuperB Workshop – 2nd June 2008
DAFNE controls tool
P. Valente – SuperB Workshop – 2nd June 2008

37. P. Valente – SuperB Workshop – 2nd June 2008
Conclusions
We have a fast, background-free, and fairly precise luminosity monitor
We are now tuning our Monte Carlo in order to have a better estimate of the systematic error
The operation of the GEM tracker [without lead shieldings] will give a much better knowledge of the acceptance
P. Valente – SuperB Workshop – 2nd June 2008

38. P. Valente – SuperB Workshop – 2nd June 2008
More slides
P. Valente – SuperB Workshop – 2nd June 2008

39. P. Valente – SuperB Workshop – 2nd June 2008
GEM tracker
70 µm
140 µm
50 µm
Gain
~20
~8000
Pads of 6×(22-32) mm2
4 detectors with 32 channels each with a total diameter of 20 cm
P. Valente – SuperB Workshop – 2nd June 2008

40. P. Valente – SuperB Workshop – 2nd June 2008
Kaon monitor
mid-mid
mid-dwne-
mid-dwne+
P. Valente – SuperB Workshop – 2nd June 2008

41. P. Valente – SuperB Workshop – 2nd June 2008
Kaon monitor
upe+-dwne-
upe--dwne+
P. Valente – SuperB Workshop – 2nd June 2008