Testing QCD Symmetries via Precision Measurements of Light Pseudoscalar Mesons

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Testing QCD Symmetries via Precision Testing QCD Symmetries via Precision Measurements of Light Pseudoscalar Measurements of Light Pseudoscalar Mesons Mesons Liping Gan Liping Gan University of North Carolina University of North Carolina Wilmington Wilmington Wilmington, NC, USA Wilmington, NC, USA

description

Testing QCD Symmetries via Precision Measurements of Light Pseudoscalar Mesons. Liping Gan University of North Carolina Wilmington Wilmington, NC, USA. Contents. Physics Motivation Symmetries of QCD QCD symmetries and Properties of π 0 , η and η ’ Experiments at Jlab - PowerPoint PPT Presentation

Transcript of Testing QCD Symmetries via Precision Measurements of Light Pseudoscalar Mesons

Page 1: Testing QCD Symmetries via Precision Measurements of Light Pseudoscalar Mesons

Testing QCD Symmetries via Precision Testing QCD Symmetries via Precision Measurements of Light Pseudoscalar MesonsMeasurements of Light Pseudoscalar Mesons

Liping GanLiping Gan

University of North Carolina WilmingtonUniversity of North Carolina WilmingtonWilmington, NC, USAWilmington, NC, USA

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ContentsContents

1.1. Physics MotivationPhysics Motivation– Symmetries of QCD Symmetries of QCD – QCD symmetries and Properties of QCD symmetries and Properties of ππ00, , ηη and and ηη’’

2.2. Experiments at Jlab Experiments at Jlab – Part I: Primakoff experimentsPart I: Primakoff experiments– Part II: Rare decays of Part II: Rare decays of ηη and and ηη’’

3.3. SummarySummary

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What is symmetry?What is symmetry?SymmetrySymmetry is an invariance of a physical system to a is an invariance of a physical system to a set of changes .set of changes .

Symmetries and symmetry breakings are fundamental in physicsSymmetries and symmetry breakings are fundamental in physics

Noether’s theoremSymmetry Conservation Symmetry Conservation

LawLaw

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Continuous Symmetrys of QCD in the Chiral Continuous Symmetrys of QCD in the Chiral LimitLimit

chiral limit:chiral limit: is the limit of vanishing quark masses mis the limit of vanishing quark masses mqq→ 0.→ 0. QCD Lagrangian with quark masses set to zero:QCD Lagrangian with quark masses set to zero:

qq

s

d

u

q

GgD

GGqiDqqiDqL

LR

s

RRLLoQCD

)1(2

1

2/

4

1

5,

)(

Large global symmetry group:Large global symmetry group:

)1()1()3()3( BARL UUSUSU

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Fate of QCD symmetriesFate of QCD symmetries

0qm

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Discrete Symmetries of QCD Discrete Symmetries of QCD

Charge: CCharge: CParity: PParity: PTime-Reversal: TTime-Reversal: TCombinations: CP, CT, PT, CPTCombinations: CP, CT, PT, CPT

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Lightest pseudoscalar mesonsLightest pseudoscalar mesons

• Chiral SUChiral SULL(3)XSU(3)XSURR(3) (3) spontaneously brokenspontaneously broken Goldstone Goldstone mesons mesons ππ00, , ηη88

• Chiral anomaliesChiral anomalies Mass of Mass of ηη00 P→→ ( P: ( P: ππ00, , ηη, , ηη׳׳))

• Quark flavor SU(3) Quark flavor SU(3) breakingbreaking

The mixing of The mixing of ππ00, , ηη and and ηη׳׳

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Some Interesting Some Interesting ηη Rare Decay Channels Rare Decay Channels

Mode Branching Ratio Physics Highlight

π0 π0 <3.5 × 10 − 4 CP, P

π0 2γ ( 2.7 ± 0.5 ) × 10 − 4 χPTh, Ο(p6)

π+ π− <1.3 × 10 − 5 CP, P

π0 π0 γ <5 × 10 − 4 C

3γ <1.6 × 10 − 5 C

π0 π0 π0 γ <6 × 10 − 5 C

π0 e+ e− <4 × 10 − 5 C

4π0 <6.9 × 10 − 7 CP, P

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The The ππ00, , ηη and and ηη’ system provides a rich ’ system provides a rich laboratory to study the symmetry structure of laboratory to study the symmetry structure of QCDQCD..

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Part I: Part I: Primakoff Program at Jlab 6 & 12 GeV

Precision measurements of Precision measurements of electromagnetic properties of electromagnetic properties of 00, , , , via Primakoff effect.via Primakoff effect.

a)a) Two-Photon Decay Widths: Two-Photon Decay Widths: 1)1) ΓΓ((00→→) @ 6 GeV) @ 6 GeV

2)2) ΓΓ((→→) )

3)3) ΓΓ((’’→→))

b) Transition Form Factors at low

Q2 (0.001-0.5 GeV2/c2):F(*→ 0), F(* →), F(* →)

Input to Physics: precision tests of Chiral symmetry and anomalies determination of light quark mass ratio -’ mixing angle

Input to Physics: 0, and ’ electromagnetic interaction radii is the ’ an approximate Goldstone boson?

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Status of Primakoff Experiments at JLabStatus of Primakoff Experiments at JLab

PrimEx-I for Γ(0) was performed in 2004 with 6 GeV beam. Published in PRL 106, 162303 (2011)

PrimEx-II for Γ(0) was carried out in 2010. Analysis is in progress.

The 12 GeV part of program has was reviewed by 3 special high energy PACs. Included in Jlab 12 GeV upgrade White paper and CDR.

PAC18 (2000)PAC23 (2003)PAC27 (2005)

The first 12 GeV Primakoff experiment on Γ(→) in Hall D was approved by PAC35 in Jan 2010.

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ΓΓ((00→→) Experiments) Experiments

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Axial Anomaly Determines π0 Lifetime

eVF

mNc 725.7576 23

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0→ decay proceeds primarily via the chiral anomaly in QCD. The chiral anomaly prediction is exact for massless quarks:

Corrections to the chiral anomaly prediction:

Calculations in NLO ChPT:Γ(0) = 8.10eV ± 1.0% (J. Goity, et al. Phys. Rev. D66:076014, 2002)Γ(0) = 8.06eV ± 1.0% (B. Ananthanarayan et al. JHEP 05:052, 2002)Calculations in NNLO SU(2) ChPT:Γ(0) = 8.09eV ± 1.3% (K. Kampf et al. Phys. Rev. D79:076005, 2009)

Precision measurements of (0→) at the percent level will provide a stringent test of a fundamental prediction of QCD.

0→

Calculations in QCD sum rule: Γ(0) = 7.93eV ± 1.5% (B.L. Ioffe, et al. Phys. Lett. B647, p. 389,

2007)

Γ(0) is one of the few quantities in confinement region that QCD canis one of the few quantities in confinement region that QCD can

calculate precisely to higher orders!calculate precisely to higher orders!

12

π

k1

k2

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Primakoff Method

2 3 42 2Pr

. .3 4

8( ) sine m

d Z EF Q

d m Q

ρ,ω

Challenge: Extract the Primakoff amplitude

12C target

Primakoff Nucl. Coherent

Interference Nucl. Incoh.

2

Pr 2

4Pr

2Pr

2

log( )

peak

peak

m

Ed

Ed

d Z E

Requirement:

Photon flux

Beam energy

0 production Angular resolution

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PrimEx-I (2004)PrimEx-I (2004)

JLab Hall B high resolution, high intensity photon tagging facility

New pair spectrometer for photon flux control at high beam intensities 1% accuracy has been achieved

New high resolution hybrid multi-channel calorimeter (HyCal)

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We measure:

incident photon energy: E and time energies of decay photons: E1, E2 and time X,Y positions of decay photons

Kinematical constraints:

Conservation of energy; Conservation of momentum; m invariant mass

0 Event selection

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Fit Differential Cross Sections to Extract Fit Differential Cross Sections to Extract ΓΓ((00) )

Theoretical angular distributions smeared with experimental resolutions are fit to the data on two nuclear targets:

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Verification of Overall Systematical UncertaintiesVerification of Overall Systematical Uncertainties

4.9 5.0 5.1 5.2 5.3 5.4 5.5

Energy (GeV)

0.055

0.060

0.065

0.070

0.075

0.080

0.085

Systematic Uncertainty

P R E L I M I N A R Y

Uncertainties:StatisticalSystematic

Compton Forward Cross Section

Klein-NishinaPrimex Compton Data

+ e +e Compton cross section measurement

e+e- pair-production cross section measurement:

Systematic uncertainties on cross sections are controlled at 1.3% level.

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PrimEx-I Result

PRL 106, 162303 (2011)

(0) = 7.820.14(stat)0.17(syst) eV

2.8% total uncertainty

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Goal for PrimEx-II Goal for PrimEx-II

PrimEx-I has achieved 2.8% precision (total) on (0) :

7.82 eV 1.8% (stat) 2.2% (syst.)

Task for PrimEx-II is to obtain 1.4% precision:

Projected uncertainties:

0.5% (stat.) 1.3% (syst.)

PrimEx-I 7.82eV2.8%

PrimEx-II projected 1.4%

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Estimated Systematic UncertaintiesEstimated Systematic Uncertainties

Type PrimEx-I PrimEx-II

Photon flux 1.0% 1.0%

Target number <0.1% <0.1%

Veto efficiency 0.4% 0.2%

HYCAL efficiency 0.5% 0.3%

Event selection 1.7% 0.4%

Beam parameters

0.4% 0.4%

Acceptance 0.3% 0.3%

Model dependence

0.3% 0.3%

Physics background

0.25% 0.25%

Branching ratio 0.03% 0.03%

Total syst. 2.2% 1.3%

Improve Background Subtraction:

Add timing information in HyCal (~500 chan.)Improve photon beam lineImprove PID in HyCal (add horizontal veto ) More empty target data

Measure HyCal detection efficiency

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PrimEx-II Status PrimEx-II Status

Experiment was performed from Sep. 27 to Nov. 10 in 2010.

Physics data collected:

π0 production run on two nuclear targets: 28Si (0.6% statistics) and 12C (1.1% statistics).

Good statistics for two well-known QED processes to verify the systematic uncertainties: Compton scattering and e+e- pair production.

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~8K Primakoff events ~20K Primakoff events

( E = 4.4-5.3 GeV)

PrimakoffPrimakoff

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ΓΓ((η→η→) Experiment) Experiment

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Physics Outcome from New Physics Outcome from New Experiment Experiment

)(2

1ˆ re whe,

22

222

duud

s mmmmm

mmQ

2. Extract -’mixing angle:

3. Determine Light quark mass ratio:

H. Leutwyler Phys. Lett., B378, 313 (1996)

1. Resolve long standing discrepancy between collider and Primakoff measurements:

            Γ(→3π) ∝ |A|2 ∝ Q-4   

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Measurement of Γ(Measurement of Γ(→→) ) in Hall D at 12 in Hall D at 12 GeVGeV

75 m

Counting House

Incoherent tagged photons Pair spectrometer and a TAC detector for the photon flux control 30 cm liquid Hydrogen and 4He targets (~3.6% r.l.) Forward Calorimeter (FCAL) for → decay photons CompCal and FCAL to measure well-known Compton scattering for control of overall systematic uncertainties.Solenoid detectors and forward tracking detectors (for background rejection)

CompCal

FCAL Photon tagger

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Advantages of the Proposed Light TargetsAdvantages of the Proposed Light Targets Precision measurements require low A targets to control:

coherency contributions from nuclear processes

Hydrogen: no inelastic hadronic contribution no nuclear final state interactions proton form factor is well known better separation between Primakoff

and nuclear processes new theoretical developments of Regge

description of hadronic processes J.M. Laget, Phys. Rev. C72, (2005) A. Sibirtsev, et al. arXiv:1001.0646, (2010)

4He: higher Primakoff cross section the most compact nucleus form factor well known

new theoretical developments for FSIS. Gevorkyan et al., Phys. Rev. C 80, (2009)

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Approved Beam TimeApproved Beam Time

Days

Setup calibration, checkout

2

Tagger efficiency, TAC runs

1

4He target run 30

LH2 target run 40

Empty target run 6

Total 79

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Estimated Error BudgetEstimated Error Budget

Contributions Estimated Error

Photon flux 1.0%

Target thickness 0.5%

Background subtraction 2.0%

Event selection 1.7%

Acceptance, misalignment

0.5%

Beam energy 0.2%

Detection efficiency 0.5%

Branching ratio (PDG) 0.66%

Total Systematic 3.02%

Statistical 1.0%

Systematic 3.02%

Total 3.2%

Systematical uncertainties (added quadratically):

Total uncertainty (added quadratically):

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Transition Form Factors at Low QTransition Form Factors at Low Q22

• Direct measurement of slopesDirect measurement of slopes

– Interaction radii:Interaction radii:FFγγγγ*P*P(Q(Q22))≈1-1/6▪<r≈1-1/6▪<r22>>PPQQ22

– ChPT for large NChPT for large Ncc predicts relation predicts relation between the three slopes. Extraction between the three slopes. Extraction of of ΟΟ(p(p66) low-energy constant in the ) low-energy constant in the chiral Lagrangianchiral Lagrangian

• Input for light-by-light scattering for Input for light-by-light scattering for muon (g-2) calculationmuon (g-2) calculation

• Test of future lattice calculationsTest of future lattice calculations

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Part II: Rare decays of Rare decays of ηη and and ηη’’

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Why Are Why Are ηη Decays Interesting for New Physics? Decays Interesting for New Physics?

Due to the conservation of G and P in the strong interaction, the η decay width Γη =1.3 KeV is extremely narrow (comparing to Γρ= 149 MeV)

η decays have the dominant strong interaction filtered out, enhancing the branching ratios for other interactions by a factor of ~100,000. η decays provide a unique, flavor-conserving laboratory to

search for new sources of C, P, and CP violation in the regime of EM and suppressed strong processes.

The heaviest member in the octet pseudoscalar mesons (547.9 MeV/c2)

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Selection Rule Summary Table:Selection Rule Summary Table:ηη Decay to Decay to ππ’s and ’s and γγ’s’s

Gamma Column

implicitly includes γ*e+e-

Key: C and P

allowed, observed

Forbidden by energy

and momentumconservatio

n.

C and Pallowed, upper

limits only

C violating,

CP conserving, etc.

L = 0

L = 1

L = even or odd (no parity

constraint).....

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Some Interesting Some Interesting ηη Rare Decay Channels Rare Decay Channels

Mode Branching Ratio Physics Highlight

π0 π0 <3.5 × 10 − 4 CP, P

π0 2γ ( 2.7 ± 0.5 ) × 10 − 4 χPTh, Ο(p6)

π+ π− <1.3 × 10 − 5 CP, P

π0 π0 γ <5 × 10 − 4 C

3γ <1.6 × 10 − 5 C

π0 π0 π0 γ <6 × 10 − 5 C

π0 e+ e− <4 × 10 − 5 C

4π0 <6.9 × 10 − 7 CP, P

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Study ofStudy of ηη→→0 0 0 0 ReactionReaction

The Origin of CP violation is still a mysteryThe Origin of CP violation is still a mystery

CP violation is described in SM by the phase in the Cabibbo-CP violation is described in SM by the phase in the Cabibbo-Kobayashi-Maskawa quark mixing matrix. A recentKobayashi-Maskawa quark mixing matrix. A recent SM SM calculation predicts BR(calculation predicts BR(ηη→→0 0 00)<3x10)<3x10-17-17

The The ηη→→0 0 0 0 is one of a few available flavor-conserving is one of a few available flavor-conserving reactions listed in PDG to test CP violation.reactions listed in PDG to test CP violation.

Unique test of P and PC symmetries, and search for new Unique test of P and PC symmetries, and search for new

physics beyond SMphysics beyond SM

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Aug 26, 2011Aug 26, 2011

Study of theStudy of the ηη→→00 DecayDecay

A stringent test of the A stringent test of the χχPTh prediction at PTh prediction at ΟΟ(p(p66) level) level Tree level amplitudes (both Tree level amplitudes (both ΟΟ(p(p22) and ) and ΟΟ(p(p44)) vanish;)) vanish; ΟΟ(p(p44) loop terms involving kaons are suppressed by large ) loop terms involving kaons are suppressed by large

mass of kaonmass of kaon ΟΟ(p(p44) loop terms involving pions are suppressed by G parity) loop terms involving pions are suppressed by G parity The first sizable contribution comes at The first sizable contribution comes at ΟΟ(p(p66) level) level

A long history that experimental results have large A long history that experimental results have large discrepancies with theoretic predictions.discrepancies with theoretic predictions.

Current experimental value in PDG is Current experimental value in PDG is BR(BR(ηη→→00 )=(2.7±0.5)x10 )=(2.7±0.5)x10-4-4

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Theoretical Status on Theoretical Status on ηη→→00

Average of Average of χχPTh 0.42 PTh 0.42

By E. Oset et al.By E. Oset et al.

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History of the History of the ηη→→00 Measurements Measurements

A long standing “η” puzzle is still un-settled.

After 1980

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High Energy High Energy η η Production ProductionGAMS Experiment GAMS Experiment at Serpukhovat Serpukhov D. Alde et al., Yad. Fiz 40, 1447 (1984)D. Alde et al., Yad. Fiz 40, 1447 (1984)

Experimental result was first Experimental result was first published in 1981published in 1981

The The ηη’s were produced with ’s were produced with 30 30 GeV/cGeV/c -- beam in the beam in the --pp→η→ηn n reactionreaction

Decay Decay ’s were detected by lead-’s were detected by lead-glass calorimeterglass calorimeter

Major BackgroundMajor Background --pp→ → 0000n n η →η →000000

Final result: Final result:

((η→η→00 ) = 0.84±0.17 eV

40 η→η→00 events events

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Low energy Low energy η η production production CB experiment CB experiment at AGSat AGS

S. Prakhov et al. Phy.Rev.,C78,015206 (2008)

The The ηη’s were produced ’s were produced with with 720720 MeV/c MeV/c -- beam beam through the through the --pp→η→ηn n reactionreaction

Decay Decay ’s energy range: ’s energy range: 50-500 MeV50-500 MeV

Final result:Final result:(η→0 ) = 0.285±0.031±0.061 eV92±23 η→η→00 events events

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η η →→00 00 00

NaI(T1)

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Major background in CB-AGS experimentMajor background in CB-AGS experiment

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data

MC

0

np

03

np

np 00

MC

MC

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CB Data Analysis II CB Data Analysis II N. Knecht N. Knecht et al. phys. Lett., B589 (2004et al. phys. Lett., B589 (2004) 14) 14

Final resultFinal result

((η→η→00γγγγ)=0.32±0.15 eV)=0.32±0.15 eV

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Low Energy Low Energy η η Production Continue Production Continue KLOE experiment KLOE experiment

B. Micco et al., Acta Phys. Slov. 56 (2006) 403 B. Micco et al., Acta Phys. Slov. 56 (2006) 403

Produce Produce ΦΦ through e through e+ee- collision at collision at √s~1020 MeV√s~1020 MeV

The decay The decay η→η→00γγγγ proceeds through: proceeds through: Φ→Φ→ηη, , η→η→00γγγγ, , 00→→γγγγ

Final result:Final result:(η→0γγ)=0.109±0.035±0.018

eV η→η→00 events events

1267

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What can be improved at 12 GeV Jlab?What can be improved at 12 GeV Jlab? High energy tagged photon beam High energy tagged photon beam to reduce the background from to reduce the background from η→ η→ 3300

Lower relative threshold for Lower relative threshold for -ray detection-ray detection Improve calorimeter resolution Improve calorimeter resolution

Tag Tag ηη by recoiled particles to reduce non-resonance by recoiled particles to reduce non-resonance pp→→0000p p backgroundbackground

High resolution, high granularity PbWOHigh resolution, high granularity PbWO44 Calorimeter Calorimeter Higher energy resolution → improve Higher energy resolution → improve 0 invariance massinvariance mass Higher granularity→ better position resolution and less overlap clusters to Higher granularity→ better position resolution and less overlap clusters to

reduce reduce background from background from η→ η→ 3300

Fast decay time → less pile-up clustersFast decay time → less pile-up clusters Large statistics Large statistics to provide a precision measurement of Dalitz plot to provide a precision measurement of Dalitz plot

30 GeV/cE 720 MeV/cE

production 1020 MeV

s

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Suggested Experiments in Hall D at JlabSuggested Experiments in Hall D at Jlab

75 m

Counting House

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GlueX FCAL

Simultaneously measure the η→0, η →00:

ηη produced on LH produced on LH22 target with target with 11 11 GeV tagged photon beam GeV tagged photon beam γγ+p+p → → ηη+p+p

Tag Tag ηη by measuring recoil p with by measuring recoil p with GlueX detector to reduce the GlueX detector to reduce the pp→ → 0000p p backgroundbackground

Forward calorimeter (upgraded with Forward calorimeter (upgraded with high resolution , high granularity high resolution , high granularity PbWOPbWO44) to detect multi-photons from ) to detect multi-photons from the the ηη decays decays

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Kinematics of Recoil ProtonKinematics of Recoil Proton

• Polar angle ~55Polar angle ~55oo-80-80oo

• Momentum ~200-1200 Momentum ~200-1200 MeV/cMeV/c

Angle θη (Deg)

Recoil θp vs θη (Deg)

Recoil Pp (GeV) vs θp (Deg) 4545

Recoil θp (Deg) Recoil Pp (GeV)

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Detection of recoil p by GlueXDetection of recoil p by GlueX

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Reconstructed missing mass and efficiency Reconstructed missing mass and efficiency

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p p

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Invariant Mass ResolutionInvariant Mass Resolution

PWO

Pb glassσ=15 MeV

σ=6.9 MeVσ=3.2 MeV

σ=6.6 MeV

M M00

M00M

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Aug 26, 2011Aug 26, 2011

S/N Ratio vs. Calorimeter GranularityS/N Ratio vs. Calorimeter Granularity

PWO

dmin=4cm

S/N=1.4

Pb Glass

dmin=8cm

S/N=0.024

4949

Background is from MC only

03

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Rate EstimationRate Estimation

23 24 20.0708 306.022 10 1.28 10 p/cm

1p A

LN N

A

The The +p+p→→ηη+p cross section ~70 nb (+p cross section ~70 nb (θθηη=1-6=1-6oo))

Photon beam intensity NPhoton beam intensity Nγγ~1.5x10~1.5x1077 Hz Hz

• The The ηη→→00 detection rate: detection rate: BR( BR(ηη→→00 )~3x10 )~3x10-4 -4 , detection efficiency ~24% , detection efficiency ~24%

7 24 331.5 10 1.28 10 70 10

1.34 Hz

115920 ' /day

PN N N

s

0

4115920 3 10 0.24 8.3 events/dayN

In order to get 10% precision on BR measurement, we need ~12 days beam time

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Statistical Error on dΓ/dMγγ for ηπ02γ

112 days

12 days

This figure gives a very rough idea how statistics limits our ability to probe

the dynamics of the ηπ02γ decay.

Assumptions are 8.3 accepted events per live

day, negligible background, and 7 bins spanning 0.025-0.375.

Prakhov et al., PRC 78, 015206 (2008).

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Experiment Figure of Merit Experiment Figure of Merit for “Forbidden Branch” Searchesfor “Forbidden Branch” Searches

In C and CP violation searches in η decays to date, it’s been true that Bkg Events >> Signal Events. Since the background fluctuations are sqrt(N), the upper limit for the branching ratio at ~95% CL is then approximately

BR upper limit ≈ 2*sqrt(fbkg*NMε)/NMε = 2*sqrt(fbkg/NMЄ)where

NM= number of mesons decaying into the experimental acceptanceЄ = efficiency for detecting products from the signal branch

fbkg = fraction of NM which remains in the signal box after all cuts

The figure of merit for experiments is therefore NMЄ /fbkg.

This means that to reduce the BR upper limit by one order of magnitude, one must either

•Increase NMЄ by TWO orders of magnitude, or •Decrease fbkg by TWO orders of magnitude.

While maintaining a competitive η production rate, Jlab would reduce BR upper limits by one order of magnitude using background reduction alone.

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How Many How Many ηη’s Can We Make?’s Can We Make?A year of Jlab operations is about 32 weeks. Assuming 50% efficiency for the accelerator and end-station, that is 112 live days.

With a 30 cm LH2 target, 70 nb cross section, and 1.5E7 gammas/second, we can produce 1.3E7 η’s per year.

The number of accepted η decays per year would be ~1/3 this, or ~4E6 per year.

η production is conservatively similar to KLOE

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Comparison of different crystalsComparison of different crystals(From R. Y. Zhu)(From R. Y. Zhu)

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Budget vs. Acceptance Budget vs. Acceptance

04/20/2304/20/23

Size of Cal.(cm2)

#crystals

# crystal needed

Crystal Cost

PMTs ADC Total

118x118

3481 2281 $0.57 M $0.68 M $0.98 M $2.23 M

150x150

5625 4425 $1.1 M $1.33 M $1.55 M $5.08 M

Beam energy (GeV)

Accp. (%) (118x118cm2)

Acc. (%) (150x150cm2)

9 9.1 27.0

10 15.8 36.0

11 23.8 44.5

12 31.1 51.1

Cost per crystal is $250, we have already 1200 crystals and PMTs from PrimEx , $300 per PMT, $281 per ADC channel

Z=600 cm, Center hole size is 10x10 cm2

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SummarySummary

A comprehensive Primakoff program has been developed at A comprehensive Primakoff program has been developed at Jlab to study fundamental QCD symmetries at low energy.Jlab to study fundamental QCD symmetries at low energy. Two experiments on Two experiments on ΓΓ((0 0 →→)) were performed.were performed.

PrimEx-I: PrimEx-I: ΓΓ((00) ) 7.82 7.82 0.14(stat.) 0.14(stat.) 0.17(syst.) eV (2.8% tot) 0.17(syst.) eV (2.8% tot)

Phys. Rev. Lett., 106, 162302 (2011)Phys. Rev. Lett., 106, 162302 (2011)

PrimEx-II was performed and analysis is in progress. The PrimEx-II was performed and analysis is in progress. The 00 lifetime at lifetime at level of level of 1.4% precision 1.4% precision is expected. is expected.

A new precision experiment on A new precision experiment on ΓΓ((ηη→→)) has been planned to run has been planned to run in Hall D at 12 GeV.in Hall D at 12 GeV.

New proposal on New proposal on rare decays of rare decays of ηη and and ηη’’ to test to test the the χχPTh PTh predictionprediction, , P, C and PC symmetries is under development. P, C and PC symmetries is under development. The goal is to significantly improve the precision of B.R. or The goal is to significantly improve the precision of B.R. or reduce the upper limits of B.R. in PDG by one order of reduce the upper limits of B.R. in PDG by one order of magnitude. magnitude.

New collaboration at any levels will be strongly New collaboration at any levels will be strongly encouraged! encouraged!

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