Transcript Spin Physics with hadron beam @ COMPASS

Marialaura Colantoni
INFN Torino Congressino
Torino 11-01-2008
COMPASS is a fixed target experiment at CERN
Beam:
Muons
Hadrons (π, p/K)
Intensity
2 108 µ+/spill (4.8s,16.2s)
Max 2· 108 h/spill
Momentum
160 GeV/c
(50 – 270) GeV/c
Polarization -80%
LHC
SPS
N
Marialaura Colantoni - INFN Torino Congressino 2008
2
Physics program @ COMPASS
 2001 → 2006 muon run with polarized (L,T) LiD target
 2007 muon run with polarized (L,T) NH3 target
 2008 hadron run with liquid H2
COMPASS contributes to the understanding
of the physics of the nucleon
Marialaura Colantoni - INFN Torino Congressino 2008
3
The COMPASS Spectrometer
Trigger-hodoscopes
μ Filter
ECal & HCal
SciFi
SM2
RICH
MWPC
SM1
GEMs
6LiD/NH3 Target
Silicon
Straws
Drift chambers
Micromegas
Two stages spectrometer
Polarized beam and target
~80%
≥50%;85%
SAT, LAT, PID
10-5<x<0.5, 10-3<Q2<100 (GeV/c)2
Marialaura Colantoni - INFN Torino Congressino 2008
4
COMPASS 2006 upgrades
 New Solenoid magnet:
Acceptance 70 mrad →180 mrad
 RICH upgrade:
Central region MAPMT system
• More photons
• Improved S/N
Outer region sampling ADC
• Improved S/N
 Other important upgrades:
Large Drift Chamber
RICHWall
Full ECAL coverage
Trigger
Marialaura Colantoni - INFN Torino Congressino 2008
5
COMPASS 2008 hadron run
Recoil Proton Detector
Beam: 190 GeV/c; 5·106 h/s; ~96% π-, ~3.5% K-, 0.5% p
Data with π-, K- beams are collected in parallel
Marialaura Colantoni - INFN Torino Congressino 2008
6
COMPASS > 2010
 Drell -Yan processes π-p→l1l2X:
 Boer –Mulders Function
 Transversity
 Sivers Functions
 …
 Deeply Virtual Compton scattering (DVCS) μp→μpγ:
 GPD functions
…
Marialaura Colantoni - INFN Torino Congressino 2008
7
Distribution functions
q(x)
momentum distribution
3 independent structure functions
describe the spin structure of the
nucleon
Δq(x)
helicity distribution
-
ΔTq(x)
transversity distribution
Marialaura Colantoni - INFN Torino Congressino 2008
8
TMD quark DFs of Nucleon
Factorization: Collins, Soper (81,82); Ji, Ma, Yuan (03, 04); Collins, Metz (04)
q
1
2
T
f (x, k )
q
1T
2
T
h (x, k )
2
T
f ( x, k )
2
T
h (x, k )
q
1T
q
1T
q
1L
Transversity: Probability to find a quark
with momentum xP, kT and transverse spin
sq in a proton with transverse spin S
2
T
g (x, k )
N
@ twist 2
q
1L
2
T
h (x, k ) h q (x, k 2 )
1
T
q
1T
2
T
g ( x, k )
Sivers Func.: Probability to find a quark
with momentum xP and kT in a proton
with transverse spin S
Boer-Mulders Func.: Probability to find
a quark with momentum xP and kT and
spin sq
Marialaura Colantoni - INFN Torino Congressino 2008
9
COMPASS DY : π-p→µ+µ-X
Bianconi, Radici Proc. Int. Work. (Trasversity 2005), Phys. Rev. D73 (2006) 1140025
A. Sissakian et al., Phys. Rev D. D72, 054027 *2005), hep-ph/0512095
q = k+k’
Use of unpolarized Drell-Yan π-p→µ+µ-X
Rˆ 



2
2
0
d
q
|
q
|
/
M
M

d

/ d

p
 T T
2
0
d
q

 T


3
can be parametrized: Rˆ 
 1  cos 2   kˆ cos 2 sin 2 
16

qT transverse momentum of virtual photon.
All angles are defined in the Collins-Sofer frame.

kˆx , x   8
 e f

x | x  x 
2 (1)
(1)


e
h
x
|

h
q q 1q   1q x p | p x  x p 

p
2
q q
(1)
1q
x  |  f1(q1)
p
p

p
First Mom. of Boer-Mulders function
Marialaura Colantoni - INFN Torino Congressino 2008
Xˆ || q
10
COMPASS DY : π-p↑→µ+µ-X
d   d 
SSA 
d   d 
Use of single polarized Drell-Yan π-p↑→µ+µ-X
φS2: azimuthal angle of the target spin vector wrt the lepton plane
SpT : target spin vector
2
sin( )
A


2
d

d

d
qT | qT | / M  sin d ( S pT )  d (S pT )
S2 


2
d

d

d
qT d ( S pT )  d (S pT )
S2 

Ψ= Φ + Φs2
Transversity
Marialaura Colantoni - INFN Torino Congressino 2008


Ψ= Φ - Φs2
Sivers
11
COMPASS DY : π-p↑→µ+µ-X
Transversity:
sin( S 2 )
A
( x , x p )  
Sivers:
sin( S 2 )
A
( x , x p )  2

2
(1)
(1)
e
h
(
x
)

h
(
x
)

h

1q
p
1q ( x )  h1q ( x p )
1 q q 1q

2
e
q q f1q ( x )  f1q ( x p )  ( x  x p )
2


2
(1)
(1)
(1)
(1)
e
f
(
x
)

f
(
x
)

f
(
x
)

f
q q 1q  1T p 1q  1T ( x p )
f1T |DY   f1T |SIDIS

2
e
q q f1q ( x )  f1q ( x p )  ( x  x p )



Collins , P.L. B536 (02) 43
Marialaura Colantoni - INFN Torino Congressino 2008
12
Drell-Yan @ COMPASS
π -p↑ →µ+µ-X ; π -p →µ+µ-X
Unique COMPASS environment:
 Intense (108 h/spill) hadron beam
 Large acceptance polarized NH3 target
 Trackers standing high rates
 Multipurpose spectrometer:
 Advanced and flexible triggering system with the possibility
to trigger on muons, electrons and hadrons
 Good hadron/electron/muon identification
 Large muon/electron acceptance
 High capacity DAQ system
 COMPASS is a running experiment
Marialaura Colantoni - INFN Torino Congressino 2008
13
COMPASS spectrometer layout
108 π/spill
25% of current PT
Trigger system to be implemented for:
• (µ+µ-) ; (e+e-);
•at least one hadron in the final state
Marialaura Colantoni - INFN Torino Congressino 2008
14
Kinematic range
Valence quarks region (x1, x2 ) > 0.1 has to be
covered
x1 → x-Bjorken of incoming quark
x2→ x-Bjorken of target quark
√s → cm energy
M2
0  x1 x2 
1
S
Q2  M 2
Enriched data sample at big Q2
M must be large enough to apply pQCD
E π-beam= 50-160 GeV
Marialaura Colantoni - INFN Torino Congressino 2008
15
Very preliminary DY events
estimation
 Target: two cells LNH3=15 cm each
 Target material: NH3
 Density of NH3: NH3 = 0.85 g/cm3
 PT material filling factor Ff = 0.6
 Number of nucleon in NH3 molecule: ANH3 =17
 - beam intensity: Ibeam = 2107 h/s
 NA = 6.0 ×1023 mol-1
Luminosity: L = LNH3 × Ncell × NH3 × Ff × NA × 1/ANH3 × Ibeam ≈
1.1×1031 cm-2 s-1
Marialaura Colantoni - INFN Torino Congressino 2008
16
Very preliminary DY events
estimation
 Compass DY pairs reconstruction efficiency (acceptance





included) : A ≈ 0.4
DY cross section on NH3: NH3 = Nnucl × p , where Nnucl=17
Dspill = 5 s (duration of spill),
Nspill =4000 (number of spills per day),
Esps= 80% (efficiency of the machine)
Duration of the Run 150 days: DRUN=150
Rate = L × Nnucl × p × A × Dspill × Nspill × ESPS × DRUN
Marialaura Colantoni - INFN Torino Congressino 2008
17
DY cross section and statistics
estimation for 150 days of running
S [GeV2]
M (+-) [GeV]
2.5-4.
M (+-) [GeV]
4.-9.
100
0.35 nb
0.03 nb
200
0.65 nb
0.10 nb
300
0.78 nb
0.15 nb
S [GeV2]
M (+-) [GeV]
2.5-4.
M (+-) [GeV]
4.-9.
100
78500
6700
200
146000
22440
300
175000
33660
Cross section values were taken from AB_5 A.Bianconi generator crosschecked with PYTHIA data (A.Nagaytsev, Dubna), without J/
contribution
Marialaura Colantoni - INFN Torino Congressino 2008
18
Expected statistical errors:
Assuming:
 the polarization of the NH3 target → 85%
 target dilution factor → 3/17
 Ntot.exp → 3.3·104 DY-events
1
A 
 3%
PT  f  Ntot.exp
without taking into account uncorrelated background
(depends on trigger selectivity)
Marialaura Colantoni - INFN Torino Congressino 2008
19
Drell-Yan Beam Test @ COMPASS,
11-12 November 2007
Marialaura Colantoni - INFN Torino Congressino 2008
20
DY Beam Test, 11-12 November 2007
Important checks:
 Hadron beam intensity & new optics (160 GeV/c negative pion beam)
 Radiation conditions in the experimental hall with:

COMPASS Polarized Target (full length (1.20 m)~ 1 int.lenght);

operation with high intensity hadron beam: 2×107 hadrons/spill
L ~10 31 cm-2 s-1 ( ~ equivalent to 108 hadrons/spill on 0.25 int.lenght PT)
 COMPASS PT performance with the high intensity hadron beam
 COMPASS spectrometer performance with high intensity hadron beam

J/ event rates (good normalization for DY and background)
 Signal/Background level and trigger rates
Marialaura Colantoni - INFN Torino Congressino 2008
21
High intensity test 2.2 107 h/spill
 Very stable spectrometer and PT behaviour
(only minor problems with few detectors)
 We are confident that we can run at luminosity of
~1031 cm-2 s-1 so that makes DY program feasible
 2.2×107 h/spill and full size PT (1 int.length↔ 1.2 m)
 108 h/spill and 0.25 of full PT (~0.3 m)
 Another crucial issue – background level – can be
evaluated after data analysis (reconstruction of events in
progress)
Marialaura Colantoni - INFN Torino Congressino 2008
22
Time line
 EoI  first quarter of 2008
 LoI  by summer 2008
 COMPASS spectrometer upgrade preparation: 2009-2010
 Muon trigger in LAS
 Modification of the central part of ECal1
 First data with pion beam after 2010
 T6 line upgrade (antiproton and kaon beam): 2013-2014?
Marialaura Colantoni - INFN Torino Congressino 2008
23
Univ. Piemonte
Orientale
Sezione di Torino
Dip. Fisica Generale
A. Avogadro
Marialaura Colantoni - INFN Torino Congressino 2008
24
Many new technologies for tracking
and PID
GEM
MicroMegas
Trigger-System
Straws
Scintillating fiber
Colantoni - INFN Torino Congressino
RICH
readout
Readout electronicsMarialaura
2008
trackers
25
Kinematic range
E π-beam= 50-270 GeV
x1 → x-Bjorken of incoming quark
x2→ x-Bjorken of target quark
M2
x1 x2 
Q2  M 2
S
M must be large enough to apply pQCD
But production rate falls off rapidly with M-4
M interval out of the resonances region has
to be selected (3.5 GeV/c2 < M < 9.0 GeV/c2)
Valence quarks region (x1, x2 ) > 0.1 has to be
covered
Marialaura Colantoni - INFN Torino Congressino
2008
26
Dose rate measurements
Heinz Vincke
2.2×107 hadrons per spill (supercycle time 20.4s)
No (additional) activation of beam line components was found
4.0 Sv/h
1.0 Sv/h
6.3 Sv/h
•
1.0 Sv/h
0.5 Sv/h
0.3 Sv/h
1.3 Sv/h
Dose rate above limits (15mSv/h):
Outside at Door PPX 221.1
Probably on balcony on Jura side upstream
of -target
Marialaura Colantoni
INFN Torino Congressino
2008
27