Drell-Yan measurements with COMPASS Basic ideas, experimental apparatus, feasibility, expected DY event rates Drell-Yan workshop Torino 05/03/2007 20/08/2019 Oleg Denisov
Contents DY at Compass Basic features of the experiment: SPS M2 secondary hadron beams Compass polarised target Compass spectrometer Major limiting factors: External (CERN safety rules) Internal spectrometer limitations Spectrometer layout in the DY MC Covered kinematical range Preliminary estimates of the DY event rates Short term plans Summary List of questions to be discussed today 20/08/2019 Oleg Denisov
DY at COMPASS 20/08/2019 Oleg Denisov
DY at COMPASS October 2004, CERN SPSC meeting at Villars – study of DY processes with COMPASS was at first time proposed and discussed (proposal by R.Bertini, O.Denisov and S.Paul) 2005 - 2007 – feasibility study (SPS hadron beams, Compass polarised target, CERN safety regulations (radioprotection), trigger system, spectrometer lay-out, possible ways of the background suppression, competition and complementarity, methods elaboration) June 2007 – EoI December 2007 – first version of the proposal 20/08/2019 Oleg Denisov
Basic features of the experiment Intense (2x107 p/sec) hadron beams Exellent large acceptance polarised target (NH3, 6LiD) Universal running spectrometer: Advanced and flexible triggering system with the possibility to trigger on muons, electrons and hadrons Good hadron/electron/muon separation in the final state Large muon/electron acceptance High capacity DAQ system Open structure of the spectrometer Compass is a running experiment 20/08/2019 Oleg Denisov
SPS M2 beam line reference person - Lau Gatignon (CERN) Compass SPS 400 GeV primary beam Production target Secondary beams Magnetic lenses Compass 20/08/2019 Oleg Denisov
Particle production at 0 mrad Apply Atherton formula for 0 mrad (approximative only for p 60 GeV/c). Obtain # particles per steradian per GeV/c and per 1012 interacting protons: 20/08/2019 Oleg Denisov
In present M2 line - beam ≈ 108 At -100 GeV/c one may expect the following beam composition (in %): Particle type Fraction at T6 Fraction at COMPASS p 1.7 2.1 K- 5.8 1.6 p- 84.5 86.3 e- 8.0 10.0 In present M2 line - beam ≈ 108 In present M2 hadron beam ≤ 2 106p (due to 108 limit on total beam flux for RP) 20/08/2019 Oleg Denisov
WHAT ABOUT A RF SEPARATEDp BEAM ??? First and very preliminary thoughts, guided by recent studies for P326 CKM studies by J.Doornbos/TRIUMF, e.g. http://trshare.triumf.ca/~trjd/rfbeam.ps.gz E.g. a system with two cavities: RF1 RF2 DUMP DUMP L Momentum selection Choose e.g. DFpp DF = 2p (L f / c) (b1-1 – b2-1) with b1-1 – b2-1 = (m12-m22)/2p2 20/08/2019 Oleg Denisov
VERY PRELIMINARY CONCLUSION H.W.Atherton formula tells us : 0.42 p / int.proton / GeV Assume target efficiency of 40% Then for 1013 ppp on target one obtains: 0.4 . 1013 . 0.42 . p . 10-5 . 2 . 0.8 ppp = 8 107 ppp for a total intensity probably not exceeding 1013 ppp, knowing that e- and p are well filtered, but K+ only partly. Due to 108 limit on total flux, max antiproton flux remains limited by purity (probably about 50%). Hence ≈ 5 107 ppp 20/08/2019 Oleg Denisov
Compass PT for DY physics Contact persons: W.Meyer, N.Doshita NH3 Polarization 90% Dilution factor 0.18 Polarization 50% Dilutionfactor 0.48 superconductive two 30 cm long 3 cm cells with opposite polarization 6LiD For transversity: 1 - + + - simultaneously reversed once a week 2 20/08/2019 Oleg Denisov
Compass spectrometer features Universal running spectrometer: Advanced and flexible triggering system with the possibility to trigger on muons, electrons and hadrons Good hadron/electron/muon separation in the final state Large muon/electron acceptance High capacity DAQ system Open structure of the spectrometer It is running spectrometer 20/08/2019 Oleg Denisov
COMPASS Universal spectrometer Polarized target (longitudinal or transversely) Have the possibility to operate with muon or hadron beams. 20/08/2019 Oleg Denisov
Compass layout for DY measurements MW1 EC HC PT Beam 20/08/2019 Oleg Denisov
Compass comparison to old fashion DY experiments Spectrometer, DY -detection Target Beam dump Compass Spectrometer, DY and e detection, “traditional” hadron beam spin physics Target Beam Dump Magnet 20/08/2019 Oleg Denisov
CERN safety regulations Reference person - Heinz Vincke (CERN) Two major limitations: Hadron beam intensity less then 5x107 p/sec Integrated material bugjet less then 20% of interaction length 20/08/2019 Oleg Denisov
CERN safety regulations There are good chance to extend these limits by: Improving the Compass area shielding Taking into account all Compass detector “heavy” components like magnets, polarised target, calorimeters, hadron absorbers etc Doing additional measurements of charged particle fluxes in the experimantal hall 20/08/2019 Oleg Denisov
Internal Compass limiting factors High charged particles flux Very selective trigger because of the small cross section +- DY channel - high background from pion decays (soft hadrons absorber?) e+e- DY channel - thick target,-conversion and Dalitz-pairs production background 20/08/2019 Oleg Denisov
Compass layout for DY measurements MW1 SOFT Hadron absorber (DUMP) EC HC PT Beam 20/08/2019 Oleg Denisov
Compass DY program beam test The Only reliable way to study the DY feasibility is to run Compass DY beam test in the real Compass environment with high intensity hadron beam and Compass polarised target 20/08/2019 Oleg Denisov
VERY IMPORTANT!!! Compass DY beam test in 2007 Conditions: Hadron beam intensity (-) – 107 p/sec Compass polarised target NH3 polarised transversally Muon program spectrometer layout VERY IMPORTANT!!! Goals: Compass polarised target test with intense hadron beam Compass spectrometer test with intense beam and thick polarised target Test for the radioactive conditions in the experimental hall with intense hadron beam and Compass polarised target 20/08/2019 Oleg Denisov
Spectrometer layout in the DY MC MW1 PT Beam 20/08/2019 Oleg Denisov
DY MonteCarlo with Compass - - beam on transversely polarized NH3 target (spin along LAB +y) - 1.0 GeV/c < PT < 10.0 GeV/c - -1 < Xf < +1 Generated 130000 events per each file with, respectively : 1. S=100 (P- = 53 GeV /c) a. 1.0 GeV <= M <= 9.0 GeV b. 1.5 GeV <= M <= 2.5 GeV c. 4 GeV <= M <= 9 GeV 2. S=200 (P = 106 GeV /c) a. 0.0 GeV <= M <= 9.0 GeV c. 4.0 GeV <= M <= 9.0 GeV 3. S=300 (P- = 160 GeV /c) a. 0.0 GeV <= M <= 9.0GeV - Processed so far, with ComGeant, 50000 events per each generated file
Compass DY MW1 and MW2 acceptance Total acceptance = m+m- in MW1 + m+m- in MW2 + m+(-) in MW1 and m-(+) in MW2 generated m+m- in MW1 m+m- in MW2 m+(-) in MW1, m-(+) in MW2 Q2 Pt Xf 67.5% 2.5% 30%
Compass DY acceptance 106 GeV - beam 1.5 <= Mm+m- <= 2.5
Compass DY acceptance 106 GeV - beam 4.0 <= Mm+m- <= 9.0 20/08/2019 Oleg Denisov
Compass DY acceptance 106 GeV - beam 0 <= Mm+m- <= 9 Acceptance S200
Compass DY acceptance 106 GeV - beam 4.0 <= Mm+m- <= 9.0
Very preliminary DY event rates estimate Target: two cells 30 g/cm2 each : LNH3=30 g/cm2 Traget material: NH3 Density of NH3: NH3 = 0.85 g/cm3 Mass of the NH3 mole: DNH3 = 17 - beam intensity: Ibeam = 2•107 p/sec Luminosity: L = LNH3 × Ncell × NH3 × NA × 1/DNH3 × Ibeam = 4.×1031 cm-2 sec-1 20/08/2019 Oleg Denisov
Very preliminary DY event rates estimate Compass acceptance: A ≈ 0.5 The muon tracks recontstruction efficiency: Reff =0.9 DY cross section on NH3: NH3 = Ncorr × p , where Ncorr=13 and p taken from table given below (by A.Bianconi) Dspill = 5 sec (duration of spill), Nspill =4000 (number of spills per day), Esps= 80% (efficiency of the machine) Duration of the Run 100 days: DRUN=100 R = L × Ncorr × p × A × Reff × Dspill × Nspill × ESPS × DRUN 20/08/2019 Oleg Denisov
DY Cross sections and statistics M (+-), GeV 1.-2.5 2.5-4. 4.-9. S, GeV2 100 5.5 nb 0.35 nb 0.1 nb 200 6. nb 0.5 nb 0.25 nb 300 6.2 nb 0.6 nb M (+-), GeV 1.-2.5 2.5-4. 4.-9. S, GeV2 100 1860000 120000 24000 200 2060000 170000 85000 300 2100000 200000 20/08/2019 Oleg Denisov
Short term DY plans DY physics with Compass spectrometer – Expression of Interest: June 2007 Compass DY Beam test: July-August 2007 DY physics with Compass spectrometer – first complete version of the technical proposal: December 2007 Proposal merging with the proposal on GPDs measurements with Compass: beginning of 2008 20/08/2019 Oleg Denisov
Summary I Compass spectrometer + SPS M2 secondary hadron beams offers a valid facility for DY physics study: Right kinematical range Compass polarised target Very universal and flexible spectrometer Two spectrometer schemes has to be examined (2007 beam test is decisive): Pure DY (+-) set-up with hadron absorber in the first spectrometer Universal spectrometer scheme, DY (+-), (e+e-), hadrons in the final state 20/08/2019 Oleg Denisov
Summary II If we are lucky we can expect statistics comparable with classical E615 and NA10 experiments Still a lot of work has to be done to prove the feasibility of the project 20/08/2019 Oleg Denisov
Proposal for discussion: DY with longitudinally polarised target (O.Teryaev) Next-to-leading-order V.Barone, O.Shevchenko Optimal kinematical range DY cross sections 20/08/2019 Oleg Denisov