1 / 41

Luminosity measurement at DAFNE

This paper discusses the use of different detectors to measure machine luminosity and diagnose interactions at the IP, including e+e- reactions and Bhabha scattering. It also presents the design and installation of the gamma monitor, Kaon monitor, and Bhabha calorimeter.

cmeredith
Download Presentation

Luminosity measurement at DAFNE

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Luminosity measurement at DAFNE M. Boscolo, F. Bossi, B. Buonomo, G. Mazzitelli, F. Murtas, P. Raimondi, G. Sensolini INFNLNF 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 <27o @1032 cm-2 s-1 • e+e-F  K+K-About 25 Hz @1032 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. 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. 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. 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. 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. Kaon monitor mips mips K mips K K K mips mips mips Courtesy SIDDHARTA collaboration Threshold P. Valente – SuperB Workshop – 2nd June 2008

  9. 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 beenoptimized 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. 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. DAQ • KLOESDS 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 calorimeterTDC and ADC boards as well as chamberTDC (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. 0 Trigger e+ 3 IP 1 e- 1 OR 2 3 T1 0 S trg 2 threshold P. Valente – SuperB Workshop – 2nd June 2008

  16. 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. 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. 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. 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. 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 t(0) t(1) t(0) t(1) P. Valente – SuperB Workshop – 2nd June 2008

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

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

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

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

  29. Simulation All 3 monitors are simulated withGEANT3 and BHWIDE generator Touschek background generator is also included main sources of systematic errors P. Valente – SuperB Workshop – 2nd June 2008

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

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

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

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

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

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

  39. GEM tracker 70 µm 140 µm 50 µm Gain ~20 ~20 ~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. Kaon monitor mid-mid mid-dwne- mid-dwne+ P. Valente – SuperB Workshop – 2nd June 2008

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

More Related