COMPASS muon programme

1
COMPASS muon programme

• Alain Magnon
• DAPNIA/SPhN (CEA Saclay)
• On behalf of the COMPASS
  Collaboration

2
Content

• Highlights about results, upgrades, prospects,
• - SPSC Villars meeting 22-28 Sept 2004
• - SPSC71 meeting 3 May 2005 (G. Mallot)
• - SPSC72 meeting 5 July 2005
• - Talks by Paolo P., Sonia H. Alex K.
  (section 4)
• Vadim A. (section 5)
• 2006 beyond ?

3
Villars 2004

• Report on the SPSC Villars Meeting
• September 22-28 2004
• John Dainton
• University of Liverpool, GB
• (on behalf of the SPSC)

4
Villars 2004

1. Framework
2. Machines and Beams
3. Heavy Ions
4. Neutrinos
5. Soft and Hard Protons
6. Antiproton Physics
7. Flavour Physics
8. Other Topics
9. Summary

• Report on the SPSC Villars Meeting
• September 22-28 2004
• John Dainton
• University of Liverpool, GB
• (on behalf of the SPSC)

COMPASS
Report on the SPSC Villars meeting by John
Dainton, University of Liverpool
(CERN-SPSC-2005-010 SPSC-M-730 February 28th
2005, available on Web)
5
COMPASS Collaboration

• Bielefeld, Bochum, Bonn (ISKP, PI), Burdwan and
  Calcutta,
• CERN, Dubna (LPP, LNP), Erlangen, Freiburg,
  Lisbon,
• Mainz, Moscow (INR, LPI, MSU), Munich-LMU,
• Munich-TU, Nagoya, Prague (CU, CUT, TUL),
  Protvino,
• Saclay, Tel Aviv, Torino (Univ., INFN), Trieste
  (Univ.,INFN), Warsaw (SINS), Warsaw (TU)
• More than 220 physicists from 28
  Institutes

6
Physics programme
Stephan Paul talk
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) -
under consideration -
Nicole dHose talk
7
Spectrometer 2002 -gt 2004
trigger-hodoscopes
DW45
straws
SM2 dipole
Muon-filter2,MW2
HCAL1
RICH_1
Gem_11
ECAL2,HCAL2
SM1 dipole
MWPC Gems Scifi
Polarised Target
SPS 160 GeV 2.108m/spill
Muon-filter1,MW1
straws,MWPC,Gems,SciFi
Veto
Gems,SciFi,DCs,straws
Silicon
SciFi
Micromegas,DC,SciFi
8
COMPASS objectives
Original programme set for about 5 years (1)
of running at 150 days/year with 14.4s
supercyle and eSPS 80.
i.e. 7.2 ? 105 spills/year i.e.
1019 PoT/year (2 ? 108 m/spill)
(1) HMC (4 years) - CHEOPS (2 years)
9
Data taking 2002 2004
2002 2003 2004
Beam (1) 106days 90d
110d ?SPSBL (2) .89
.63 .67 Preparation 30d
7d 3d ?Spectro(3)
.77 .83 .87 Data taking (4) 44d
39d 61d muon (L/T) 33d/11d
30d/9d 47d/14d
2004 19d 4d 15d hadron
(1) Scheduled beam excluding MDs (4) L/T
Longitudinal/Transverse sharing 80/20 (2)
Inefficiency from SPS, beam line, etc (3) 0.90
additional due to time needed to rotate spin and
calibrate spectrometer
10
Data taking 2002 - 2004
muon 2002 2003 2004 -gt 11.6 ? 105
spills request 7.2 ? 105 spills/year ? 2.5
(proposal-year)
We got 1.6 (proposal-year)
Pilot hadron run 2004 -gt 0.7 ? 105 spills
11
Physics results

• Highlights (SPSC71 status report)
• - g1
• - transversity
• - L polarisation
• -DG/G from high pT hadron pairs
• -DG/G from open-charm
• - more

12
g1 of the deuteron
2002-2003 data

• most precise measurement for 0.004 lt x lt 0.03
  PLB 612 (2005) 154
• new NLO QCD fit, precision of a0 improves factor
  2 (ltQ2gt 4 GeV2)

13
Towards transversity

• single transverse-spin asymmetries (2002 data)
• - Collins related to transverse quark
  distributions
• - Sivers related to intrinsic kT

h
h-
Collins
PRL 94,202002 (2005)
Sivers
14
Quark polarimeters

• all asymmetries compatible with zero
• measure product of chiral-odd FF and
  transverse-PDF
• - is the analysing power of Collins FF small?
• or are the transverse parton distributions small?
• (proton-neutron cancellation in deuteron ?)
• try other polarimeters
• - interference FF of two hadrons
• - lambda polarisation

15
Theoretical work on Sivers SSA

• Extracting the Sivers function from polarized
  SIDIS data and making predictions
• - Phenomelogical model whose parameters are
  constrained by HERMES proton measurements.
• - COMPASS 2002 preliminary results for Sivers
  effect are in agreement with the model.

M. Anselmino et al. hep-ph/057181 (including
HERMES Prel. Results shown at DIS05)
16
Theoretical work on Sivers SSA
Predictions of Sivers asymmetries on a proton
target
M. Anselmino et al. hep-ph/057181
17
Expected accuracy for Collins asymmetries
2002 2002-4
2006

18
?G/G from Photon-Gluon Fusion

• Strategies to suppress background
• 1) Open charm production
• q c unique, no background
• charm fragmentation, 1.2 D0 per event
• D0 -gt K- p (BR 4), D(20) -gt D0 p
• 2) High-pT hadron pair production qu,d,s
  background from
• non PGF events resolved g
• pQCD scale set by
• 1) s gt 4mc2 or
• 2) s gt (pt1pt2)2

LOW STAT.
HIGH STAT.
Photon Gluon Fusion
Needed since Q2 0
19
?G/G from high-pT hadron pair
e, m
h1
h2
N
Photon Gluon Fusion
Leading order Process
QCD-Compton
measured
aLL calculable partonic asymmetries R
Monte-Carlo (Lepto/Phytia depending on Q2)
20
high-pT hadron pairs
Q2lt1GeV2 Q2gt1GeV2

• Q2 lt 1GeV2 250000 evts
• Q2 gt 1GeV2 28000 evts
• 2002 and 2003 data
• - pT,1, pT,2 gt 0.7 GeV, p2T,1 p2T,2 gt 2.5
  GeV2,
• - for statistical reasons use A / D
• - D depolarisation factor,
• - exact formula used in analysis

21
high-pT hadron pairs Q2lt1GeV2

• more difficult than large Q2
• contributions from resolved photons
• - spin dependent structure of the photon
• perturbative part calculable
• non-perturbative part
• - min/max VMD scenarios (Glück, Reya, Sieg)
• - tuning of intrinsic kT partons in the photon
• nucleon parameters
• - tuning of fragmentation functions
• - tuning of intrinsic kT in nucleon

22
Gluon polarisation, high pT pairs
Q2gt1GeV2
2002-2003 data
Q2lt1GeV2
23
Gluon polarisation
?G 2.48
?G 0.62
?G 0.16
GRSV2000 NLO fits to g1 m2 3 Gev2
?G/G (xg 0.1) is small
DGgt1 disfavoured
24
Open charm Ds from Ds

• requiring the slow pion in D ? D ps? K p ps

D0 ? K p p0
25
Gluon polarisation, D0 D events
2002-2003 data
DG/G -1.08 /- 0.73 ltxggt 0.15 /-
0.08
26
Gluon polarisation
?G 2.48
?G 0.62
?G 0.16
GRSV2000 NLO fits to g1
27
Figure of Merit for open charm
FoM

• 2002 2004 -gt 2006
• FoM(DG/G)
• s(DG/G)1/FoM1/2
• We work very hard to increase FoM

28
Figure of Merit for open charm

• FoM increase in 2006 (with upgrades)
• New COMPASS magnet 1.3
• Rich upgrade 1.5
• Ecal 1.2
• K below threshold 1.1
• 100 days of beam 1.3 -gt ( .9)
• total 3.4 -gt (2.4)

29
Large Angle Spectrometer 2002-3-4-6
DC1 DC2 DC4 Straws
end 2002 downstream of SM2
Initial lay-out
200 mrd
COMPASS PT solenoid
Modified
.....
70 mrd
SMC solenoid
Straws 1 1/2 2?1/2
DCs 3
30
COMPASS Oxford Danfysik magnet

• OD magnet presently tested and
• instrumented in Saclay
• Some delays ...
• Magnet will be delivered to CERN
• in November

31
COMPASS OD magnet
1st attempt to get uniform field (24.06)
encouraging
100 ppm
Request is 100 ppm
32
RICH (PDs) upgrade in 2006
33
RICH upgrade in 2006

• central region maPMT
• multi-anode PMTs
• lens system
• MAD4 preamp
• F1 TDCs, excellent time resolution
• outer region APV
• keep CsI photodetector
• new readout based on APV chips
• good timing resolution
• no DAQ dead time

beam
34
RICH maPMT

• elements tested in T11 beam
• approved by INFN in April, design of
• optics finished, PMs ordered (600)
• delivery schedule Q3 2005 till Jan 2006
• ready spring 2006

Trieste, Turin Bonn, Erlangen, Freiburg,
Lisbon, Mainz, Prague (2)
35
APV RICH project
dR, cm
Trigger time x25ns

• R/O successfully tested during 2004 on the Rich
• installation and test Q1 /06

• Design based on GEM Si FEE
• Provides signal timing
• accuracy lt200ns

TU-Munich, Saclay
36
Large drift chamber DC4

• Chamber under construction by Saclay
• frames delivered
• assembly and test Q4/05-Q1/06
• operational April 2006

37
ECAL1

• Plan to equip entire ECAL1 for 2006 (Protvino)
• Also beneficial for open-
• charm
• D0 ? K p p0
• D0 ? D0 p0s

38
SPS in 2006
Schedule prepared by SPS Coordinator
proposed by SPSC COMPASS - 2006 3440 hgt 142
days COMPASS (2004) 3120 hgt 130 days
110(m) 20(h)
39
SPS in 2006
Schedule was not accepted by CERN RB
New (draft) schedule

• COMPASS 2006
• 2728 hgt 113 days (not 142 d)
• restart of SPS etc
• ?SPSBL 0.7 or lower
• 0.5 proposal year

40
Conclusion

• muon programme was for 2.5 years (SPS
  proposal-years)
• with 1.6 year of running, important physics
  results were
• obtained, also
• - 3 physics papers (g1d, Collins/Sivers asym.,
  penta-q search)
• - DG/G with remarkable precision from high pT
  low Q2
• - s(DG/G) from D0 (0.73 -gt 0.43 with 2004)

41
Conclusion

• Ambitious objective for 2006
• Complete proposed muon programme
• - get error on DG/G from charm close to error
  of proposal,
• - run both with deuteron proton target
• 1/ successful equipment upgrades
• 2/ sufficient beam allocation from SPS (?)

42
Additional slides
43
s(h1d,h1p) vs acceptance
COMPASS magnet
SMC magnet
44
Resolved photon contributions
PYTHIA
e.g. qq? qq
45
Example kT tuning
nucleon
photon

• systematic error
• - determined using 15 independent MC simulations
• - exploring the parameter space
• in kT of nucleon and photon
• fragmentation functions
• parton shower on/off,
• renormalisation scale

46
Data versus MC

• excellent to good
• agreement for all
• kinematics variables
• lets get

47
Data versus MC

• excellent to good agreement
• for all kinematics variables
• lets get

48
high-pT hadron pairs Q2gt1GeV2

• xBj lt 0.05, can neglect QCD Compton and LO
• LEPTO tuning à la SMC high-pT

x
pT
p
49
Open charm MC studies
pT
z
y

• AROMA Monte Carlo, PGF only
• background subtracted 2003 data (side bands)
• Ds indeed from PGF ? Data understood?
• good agreement data / MC
• hard z-distribution

50
Open charm MC studies

• aLL from one hadron from PGF reconstructed
• Correlation of generated and reconstructed aLL
• Analysis uses event weighting with aLL deduced
  from hadron kinematic variables

51
RICH upgrade in 2006