1. COMPASS status & near future
Alain Magnon
DAPNIA/SPhN (CEA Saclay)
On behalf of the COMPASS Collaboration
A.Magnon
Villars Sept 24, 2004

2. Content COMPASS, some history Spectrometer Data taking 2002 to 2004
Results: highlights & projections
Near future , SPS beam
Higher proton intensity, >
A.Magnon
Villars Sept 24, 2004

3. COMPASS genealogy/calendar
COMMON
MUON and
PROTON
APPARATUS for
STRUCTURE and
SPECTROSCOPY
1996: last SMC year … and COMPASS
proposal
1997: conditional approval
1998: MoU, September
1999 – 2000: construction and installation
2001: commissioning run
: data taking
© G. MALLOT
A.Magnon
Villars Sept 24, 2004

4. COMPASS Collaboration
Bielefeld, Bochum, Bonn (ISKP, PI), Burdwan and Calcutta, CERN, Dubna, Erlangen, Freiburg, Heidelberg, Helsinki, Lisbon, Mainz, Moscow (INR, LPI, MSU), Munich (LMU, TU), Nagoya, Prague, Protvino, Saclay, Tel Aviv, Torino (Univ., INFN), Trieste (Univ.,INFN), Warsaw (SINS, TU)
More than 220 physicists from 28 Institutes
A.Magnon
Villars Sept 24, 2004

5. Hadron structure and spectroscopy
Physics programme
Hadron structure and spectroscopy
Muon beam programme
Quarks and gluon polarisation
in polarised (longitudinal) nucleons
Transverse spin distribution
Lambda polarisation
Diffractive vector-meson production
Hadron beam programme
Polarisibility of pions and kaons
(Primakoff reaction)
Exotics q-states, glue balls
Semi-leptonic decays of charmed baryons
Double charmed hadrons
GPDs (DVCS, HEMP) see N.D’Hose talk
- under consideration -
A.Magnon
Villars Sept 24, 2004

6. Imperative to measure ΔG
Quark & gluon spin
Nucleon spin: ½ = ½ ΔΣ + ΔG +<Lz >
In polarised DIS, one measures
flavor singlet axial matrix element
a0 = ΔΣ – (as/2p)nf ΔG
All experiments (SLAC,EMC,SMC,
SLAC, HERMES) confirm:
a0 ~ 0.1 ÷ 0.2
Imperative to measure ΔG ??
A.Magnon
Villars Sept 24, 2004

7. COMPASS acceptance
Excellent for non-perturbative & perturbative physics
- small xBj & very small Q2  Q2 > 100 (GeV/c)2
A.Magnon
Villars Sept 24, 2004

8. Spectrometer 2002 -> 2004 trigger-hodoscopes SPS 160 GeV
DW45
straws
SM2 dipole
Muon-filter2,MW2
RICH_1
HCAL1
Gem_11
SM1 dipole
ECAL2,HCAL2
Polarised Target
MWPC Gems Scifi
SPS 160 GeV
2.108m/spill
Muon-filter1,MW1
Veto
straws,MWPC,Gems,SciFi
Gems,SciFi,DCs,straws
Silicon
SciFi
Micromegas,DC,SciFi
BMS
A.Magnon
Villars Sept 24, 2004

9. Polarized target system
3He – 4He dilution
refrigerator (T~50mK)
+dipole magnet (0.5T) μ
Reconstructed
interaction vertices
A.Magnon
Villars Sept 24, 2004

10. COMPASS/Oxford-Danfysik solenoid
December 2003 :
MoU CERN/DAPNIA/COMPASS
finalize instrumentation and
magnetic tests
2004 : Agreement with OD
delivery to Saclay
perform cold acceptance tests
delivery to CERN
2005 : Installation CERN, tests, magnetic measurements, polarization
A.Magnon
Villars Sept 24, 2004

11. PID with RICH1 3 m 116 VUV mirrors, surface area: 21 m2 6 m 5 m
photon
detectors:
CsI MWPC
mirror
wall
vessel
radiator:
C4F10
Photon detection
5.3 m2 MWPCs
16 CsI Photocathodes
84,000 analog readout channels
single photon: s =1.2 mrad
ring: s =0.4 mrad
photons/ring n ~14
3s p /K sep. up to 40 GeV/c
detection of
VUV photons
( nm)
A.Magnon
Villars Sept 24, 2004

12. COMPASS objectives Original programme set for about 5 years (1) of
running at 150 days/year i.e. 7.2105 spills
with 14.4s supercyle and eSPS = 80%.
2108 m/spill equivalent to ~ 1019 protons/year.
(1) HMC (4 years) - CHEOPS (2 years)
A.Magnon
Villars Sept 24, 2004

13. Data taking 2002 – 2004
(Oct 4)
Beam (1) days 90d d(5) (+16d)
єSPS+BL (2) ~.64
Preparation ~30d d d
єSpectro(3)
Data taking (4) d d d (61d)
muon (L/T) d/11d 30d/9d 32d/14d
2004
19d 4d
15d
hadron
(1) Scheduled beam excluding MDs (5) Update September 17, 2004
(2) Inefficiency from SPS, beam line, etc
(3) ~0.90 additional due to time needed to rotate spin and calibrate spectrometer
(4) L/T Longitudinal/Transverse sharing 80/20
A.Magnon
Villars Sept 24, 2004

14. Data taking 2004
Thanks to the excellent performances of spectrometer and to the 2 weeks prolongation of SPS running, our expected goal in statistics for 2004 is still in reach
A.Magnon
Villars Sept 24, 2004

15. Data taking 2002 - 2004 muon: 2002 + 2003 + 2004 -> 11.3105 spills
hadron: > ~ 0.5105 spills
If things go very well in 2004, we will have at the end of 2004 ~ 1.5  proposed year
A.Magnon
Villars Sept 24, 2004

16. Physics results Longitudinal spin : DG/G – from open charm
DG/G - Spin asymmetry from high pT hadrons pairs
A1d
Flavour decomposition of polarized PDF
Transverse spin : Collins/Sivers asymmetry
Λ & Λ hyperons, production and polarization
Vector meson production ρ, φ and J/ψ.
Exclusive r production
A.Magnon
Villars Sept 24, 2004

17. Exclusive r0 production (1)
If SCHC holds ->
High precision measurement
of spin density matrix element
2002 data (only)
A.Magnon
Villars Sept 24, 2004

18. Transverse spin Collins asymmetry
ΦC = Φh + ΦS – π
A = A0 ± A1 sin(ΦC)
AColl = A1 / (DNN.f.P)
AColl h1q(x,Q2) h+ h-
xBJ
zhad
A.Magnon
Villars Sept 24, 2004

19. “Longitudinal spin virtual photon asymmetry”
A1d from inclusive scattering
“Longitudinal spin virtual photon asymmetry”
2002 data only
DIS evts
Q2 > 1 GeV/c2
0.1 < y < 0.9
beam time COMPASS / beam time SMC = 1 / 7
A.Magnon
Villars Sept 24, 2004

20. ΔG/G from high pT hadrons pairs
Leading process
Gluon radiation (Compton)
Photon Gluon Fusion
(PGF) -
preliminary (2002 data)
Ag*d = ± (stat) ± (syst)
Assuming (Phytia-LO) : R_PGF ~ ¼
s(ΔG/G) ~ 0.17
“ΔG/G” = 0.**
A.Magnon
Villars Sept 24, 2004

21. ΔG/G from open charm Photon-Gluon-Fusion: 1.2 D0 per PGF cc event
¾2002 (25 “days”)
317 (D*)D0
SEFF(*) ~ 120 c
D0 K-p+
(BR = 4%) c
(*)SEFF=S/(1+B/S)
A.Magnon
Villars Sept 24, 2004

22. FoM = (Pm  PT  f  <aLL>)2  [SEFF=S/(1+B/S)]
ΔG/G from open charm
s(DG/G) = 1/(FoM1/2)
FoM = (Pm  PT  f  <aLL>)2  [SEFF=S/(1+B/S)]
(~.76  ~.50 ~.40  ~.22 )2  SEFF
FoM2002 ~  120 = 0.14
FoM2002 -> s(DG/G) ~ 2.7
A.Magnon
Villars Sept 24, 2004

23. Figure of Merit, assessment/improvement 2002 -> 2003 -> 2004
Very big effort made to obtain a detailed understanding of our FoM (tracking, RICH reconstruction … etc) see COMPASS note
A.Magnon
Villars Sept 24, 2004

24. Figure of Merit, assessment/improvement 2002 -> 2003 -> 2004
COMPASS note , projection
Update
A.Magnon
Villars Sept 24, 2004

25. Figure of Merit, assessment/improvement 2002 -> 2003 -> 2004
33 “days” (L)
SEFF=151(8)
2003
30 “days” (L)
SEFF=674(17)
2004
5 “days” (L)
SEFF=112(7)
2002 -> 2003(4)
SEFF/day  4.9
18 / 4.9 = 3.6
A.Magnon
Villars Sept 24, 2004

26. Projection for s(DG/G) from D0
FoM2002 =
 Rnb of days =112/25
rFoM ~ 18
(D0+D*)/D* ~ 1.5
FoM( ) ~ 17
s(DG/G) = 0.24
A.Magnon
Villars Sept 24, 2004

27. Projection for s(DG/G), D0 & high PT
If 2004 statistic & FoM as expected
projection for data :
s(DG/G) = 0.24 (D0)
s(DG/G) = 0.05 (high pT all Q2)
s(DG/G) = 0.16 (high pT Q2>1GeV2)
ssyst from
resolved g +
LO/NLO ??
HELP from
theorists !!
s(DG/G) proposal = 0.14
A.Magnon
Villars Sept 24, 2004

28. COMPASS near future (2006 ->), goals
Increase global efficiency (FoM/day) by factor ~ 2 :
- Larger acceptance with OD magnet
- Improve RICH efficiency/purity
(software & hardware for central photon detectors)
- Improve tracking
Take proton data (NH3 target)
- Flavor separation of DS & transversity
A.Magnon
Villars Sept 24, 2004

29. COMPASS near future (2006 ->)
Hadrons: 2.5150 days (proposal)
D0 -> s(DG/G)(2)
0.17
0.11
Muons, 2 scenarios:
NH3(1) 150 days (proposal)
6LiD + NH3 2150 days
- 6LiD/NH3 (50/50)
(1)FoM(NH3) ~ 0.3FoM (6LiD)
(2)assuming FoM3.92
s(ACollins) reduced by 3 ÷ 6
for proton and D
A.Magnon
Villars Sept 24, 2004

30. Beam from SPS beyond (2006 ->)
From CERN-AB OP/RF
FT request:
150 days/year
~ 7.2 105 spills/year
Separation of CNGS/FT operations ?
Increase available proton flux ?
Longer SPS operation
CNGS request:
4.5 1019 protons/year
A.Magnon
Villars Sept 24, 2004

31. COMPASS beyond 2010 Increase available proton flux by a factor of ~ 5
- Only solution for dilemma of beam sharing ?
- Longitudinal physics, DG/G at several xG,
(DG/G) from g1(x,Q2) evolution
- Transverse physics, xB, zh, Q2 & pT dependence of
Collins asym., T-distribution for s quark ... etc
Requires major upgrade of:
- M2 beam line & COMPASS spectrometer
A.Magnon
Villars Sept 24, 2004