Physics with Muon and Hadron Beams at COMPASS
Reiner Geyer for the COMPASS collaboration
Hadron Structure 2009
Daniele PanzieriEINN07 - Milos 12-15 september
2007
N
SPS
LHC
SPS Beams: protons up to 400 GeV/c. 4.8s/16.2 spillSecondary hadron beams (p,π±,K±) with 2·108 particles/spillTertiary Muons: 2·108 particles/spill with 80% polarization
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The COMPASS Collaboration Bielefeld, Bochum, Bonn (HISKP), Bonn (PI), Burdwan and Calcutta, CERN,
Dubna (LPP and LNP), Erlangen, Freiburg, Mainz, Lisbon, Moscow (INR), Moscow (LPI), München (LMU), München (Technische Universität), Prague, Protvino, Saclay, Tel Aviv,
Torino (University and INFN), Trieste (University and INFN), Warsaw (SINS), Warsaw (TU), Yamagata
240 Physicists from more than 20 Institutes
Experiments with Muon Beam- ΔG/G- g1
- Transverse Spin Effects- Flavor Decomposition of Spin
Distribution Functions- Excl. Vector Meson Production- Lambda Polarizations
Future:- DVCS
Experiments with Hadron Beams- Pion and Kaon Polarizabilities-Diffractive Production of Exotic States-Search for Glueballs-Light Meson Spectroscopy
Future:- Drell Yan
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Historical Overview
• 2002, 2003, 2004, 2006 and 2007 data taking with 160 GeV, polarized μ beams:– 2002-2006 6LiD polarized target (~polarized deuterons)– 2007 NH3 polarized target (~polarized protons)– Both longitudinal and transverse polarized targets.
2000 TB of data corresponding to 5·1010 events
• Pilot run in 2004 for hadron program• Few days of effective data taking.
• 2008: Hadron Beams for diffractive scattering.
Physics Results• Muon Beams: ΔG/G, ΔΣ, Transversity, Flavor
Decomposition, Pentaquark, Exclusive Production of Vector Mesons, Cahn Asymmetries.
• Hadron Beams: PWA in diffractive Scattering.
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Polarized Deep Inelastic ScatteringH
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The First Moment of g1
• first moment of g1
“Spin crisis”EMC 1987
Contrary to naive expectations, the spin of the nucleon is not only carried by the quarks.
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From COMPASSH
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Error is a factor 2 bigger without COMPASS
NLO QCD Fit of world data
ΔΣ = Δu + Δd + Δs =0.30 ± 0.01(stat)±0.02(evol)
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Where is the Proton Spin
From the pattern of the spin structure functions we expect more generally:
Experiment
ΔΣ = Δu + Δd + Δs
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Flavor decomposition of Nucleon StructureS
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Alexander Korzenev:Measurement of the Spin Structure of the Proton by COMPASS
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Direct measurement of ΔG/G
Two approaches to tag PGFin COMPASS
• q = c:
Open CharmD0, D* decay
• q = u, d, s:
High-pt Hadron Pairs
Photon Gluon Fusion(PGF)
Photon Gluon Fusion'
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• Spin dependence of the basic-processes calculable via pert. QCD
P
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ΔG/G from High pt Hadron Pairs H
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Q2>1Dominated
by:
Open charm production dominated by PGF:Cleanest but most difficult to measure!
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Open charm at COMPASS
• Photon-gluon fusion: 1.2 D0 per PGF cc event
c
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-0 KD BR 4 %
s
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0*
K
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D0 from D* about 20 %
or:
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The Compass Spectrometer
SM1
SM2
Beam
MuonWall
MuonWall
E/HCAL
E/HCAL
RICH
Target
Two-stage spectrometer• Tracking: VSAT+SAT+LAT
• Particle Id: RICH, m• Calorimetry: ECAL, HCAL
• ~250000 channels• up to 580 TB/year recorded
Two-stage spectrometer• Tracking: VSAT+SAT+LAT
• Particle Id: RICH, m• Calorimetry: ECAL, HCAL
• ~250000 channels• up to 580 TB/year recorded
• m/h beam: 160/190 GeV• high beam intensity
• large angular acceptance• broad kinematical range
• m/h beam: 160/190 GeV• high beam intensity
• large angular acceptance• broad kinematical range
50 m
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The Compass Spectrometer
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Particle ID - The RICHH
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Kπ Mass SpectrumH
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ΔG/G Results
Interest in Orbital MomentumGPDs
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Physics with Transverse SpinH
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Christian Schill: Transversity Measurements at COMPASSStefano Takekawa: Spin physics in polarized Drell-Yan processes at COMPASS
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Meson SpectroscopyH
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Exotic States ?H
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Hybrids Candidates
Glueball Candidates
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Diffractive Scattering and Central ProductionH
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First Results from the 2004 Pilot RunH
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PWA TechniqueH
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Waves used in step 1of PWAS
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Major WavesH
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π1(1600) H
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COMPASS in 2008H
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Target RegionH
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TriggerH
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Statistics in 2008H
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π-p π-π+π-π+π-p, π-π0π0p, π-ηηp, π-π0p; K- p K
-π+π-p
Matthias Schott: Physics with Kaons in the Final State
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Hadron Run 2009H
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• Spectroscopy with positive beam – p beam with 25% pions, 190 GeV, LH2 target– “Central production”
• Spectroscopy with negative beam– π− beam with 3% kaons, 190 GeV, LH2 target – Diffraction with LH2 target (low t) – Diffraction with nuclear target– Primakoff Scattering
• Studies for future program (needed for delevopments)– DVCS test with muon beam and recoil det. – Drell-Yan test with π- beam
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Proposal to Study DVCS at COMPASSH
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Kinematical Range at COMPASSH
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Feasibility Studies 2008H
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1 day measurement1/3 μ-intensity
1/6 of target length
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Summary
• Muon Program– New results on polarized PGF and gluon polarizations.– New results on Transversity Christian Schill.– New results on flavor decomposition of nucleon structure.– More data taking on longitudinal and transversal polarized
proton target (2010 & 2011) in order to improve statistics.
• Hadron Program– Results on diffractive 3 π production from 2004 pilot hadron
run.– A lot of new results to be expected from 2008 and 2009 on
diffractive scattering and central production in different final states.
• Feasibility studies for DVCS and Drell Yan ongoing. Proposal under preparation. If successful data taking from ~ 2012 on.
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More Talks from COMPASS @ HS2009
Christian Schill:
Transversity Measurements at COMPASS
Alexander Korzenev:
Measurement of the spin structure of the proton by COMPASS
Alexey Guskov:
The possibility of pion polarizabilities measurements at COMPASS
Matthias Schott:
Studies of Kaonic final states at COMPAS
Stefano Takekawa:
Spin Physics in polarized Drell-Yan processes at COMPASS
Ekaterina Perevalova:
Logitundinal polarisation of the Λ and Λ-bar hyperons in DIS @ COMPASS
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