Physics with Muon and Hadron Beams at COMPASS

Reiner Geyer for the COMPASS collaboration

Hadron Structure 2009

Daniele PanzieriEINN07 - Milos 12-15 september

2007

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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

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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

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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

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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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