sixth international conference on perspectives in hadronic physics hard photodisintegration of a...
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Sixth International Conference on Perspectives in Hadronic Physics
Hard Photodisintegration of a proton Pair
n(slow) )p(high p )p(high p He tt3 ++→γ
12 - 16 May 2008(Miramare - Trieste, Italy)
Tel Aviv University ,
Tel Aviv, Israel
E. Piasetzky
Kinematics:
)sin( )(sin 2
1 cm
2 θθ γγ EMEp cmdt ≈=
1) (4 M 2 M ) ( d2
d2 +≈+=+= γγγ EEpps d
]1)[cos(2E ]1)[cos( 2
M - s ) - (
2d2 −≈−≈= cmcmNppt θθ γγ
0cm 90 FOR =θ
GeV/c 1.5 p , 4 t,GeV 12 s GeV 2 t22 ≈−=≈= GeVEγ
GeV/c 2.5 p , 10 t,GeV 24 s GeV 5 t22 ≈−=≈= GeVEγ
photodisintegration is an efficient way to reach the hard regime.
To obtain the same s in NN scattering Pp ~ 2 Pγ.
γ
p
d/pp
n/pLAB
γ d/ppn/p
pGeV 5 - 2 =γE
CM
High – energy photodisintegration of the deuteron
npd ),(γ
The bremsstrahlumg endpoint technique:
It is enough to measure the proton momentum vector
The incident photon energy
The recoil neutron kinematics
Assuming two-body reaction
To ensure two-body reaction the reconstructed photon energyIs limited to the endpoint – the π mass
d
p
n
p
n
γ
Radiator
PhotonElectron
3Hep
p
µµ
HRS
n
θRadiator
PhotonElectron
d
npd ),(γ
Backgrounds are subtracted by “radiator out” and empty target runs
Build in quality-control – empty region beyond the endpoint
Exclusive large-momentum-transfer scattering
)f( S st)2-n(N- A DCB nnn
CDABdt
d +++=
→∝
σ
N = 1 + 6 + 3 + 3 – 2 = 11
) ( ) ( tt phighnphighpd +→γFor
Notice:
410 GeV/c) 4( / GeV/c) 1( ≈== γγσσ
Edtd
Edtd
scaling
•Dimensional (Constituents) counting rule:
(GeV) γE
)(GeV 222dmW −
Δ(1232)
N*(1520)D13 ?
Leading order pQCD underestimates cross sections for intermediate energy photo - reactions
Deuteron elastic form factor
FF (Q2 = 4 GeV2) calculation/data < 10-3
Meson photoproduction
Real Compton scattering
)pQCD scaling scaling --\ pQCD(
Farrar, Huleihel, Zhang PRL 74, 650 (1955)
Farrar, Huleihel, Zhang NP B 349, 655 (1991)
Brooks, Dixon PRD 62 114021 (2000)
p
n
d
Millions of diagrams like this
The observation of the scaling indicates the onset of the quark – gluon degrees of freedom, the appropriate underlying physics is not Leading order perturbative QCD.
γ
How to use experimental data to replace sum over many diagrams
Theoretical models:
How the photon is coupled
What diagrams can be neglected
p
n
dF (p)
F (n)
F (p)
F (n)
RNA (Reduced Nuclear Amplitude)
Experimental nucleon FF gluon exchanges within the nucleons
Neglect diagrams with gluon exchanges between the nucleons
Photon can interacts with any quarks
)(p
1 (n)F (p)F
)m-(s
1 2
2t
2222
dcmf
dt
d θσ∝
Brodsky , Hiller PRC 28, 475 (1983)
p
n
dF (p)
F (n)
F (p)
F (n)
TQC (Two - Quark Coupling)
gluon exchanges within the nucleons Experimental nucleon FF
Photon interacts with the exchange pair of quarks
)()(
1 (n)F (p)F
)m-(s
1 2
222
22d
cmfsdt
d θσΛ−
∝
Radyushkin
gluon exchanges between the nucleons neglected
p
n
d
HRM (Hard rescattering Model)
p) (2 lowdψ
qTγ
NNNNT →
Convolution of large angle pn scattering amplitude , hard photon – quark interaction vertex, and low momentum nuclear wave function
The pn scattering amplitude is obtained from large angle pn data
Frankfurt, Miller, Sargsian, Strikman PRL 84, 3045 (2000).
Quark – Gluon String model (QGS)
3 q exchange with an arbitrary number of gluon exchanges
Regge theory - nonlinear trajectory
Grishina et al. EUR. J. Phys. A 10, 355 (2000)
pn
d F(
F
F
F
)(p
1 (n)F (p)F
)m-(s
1 2
2t
2222
dcmf
dt
d θσ∝
pn
dp) (2 lowdψ
qTγ
NNNNT →
)()(
1 (n)F (p)F
)m-(s
1 2
222
22d
cmfsdt
d θσΛ−
∝
dN N
g
See M. Sargsian talk
RNA
HRM
CQM
QGS
See Sargsian talk
How are such large transverse - momentum nucleons produced?
Breaking a transverse compact object formed before the absorption?
) GeV/c 2 p ( ≈dψDouble hard scattering?
) MeV/c 300 P ( ≤dψ
But comparing calculations with the data do not reveal the underlying
physics .
RNA
HRM
Hard Photodisintegration of a proton pair
n(slow) )p(high p )p(high p He tt3 ++→γ
What new can we learn from that?
How are such large transverse momentum nucleons produced ?
Transitions from meson exchange to quark exchange
Scaling
Oscillations
3He
p
p
n
p
pµµ
HRS
HRS
Radiator
PhotonElectron
nppH e ),(3 γThe bremsstrahlumg endpoint technique
High – energy photodisintegration of a proton pair in 3He
Experiment E03-101
JLab. June 2007
a spectator neutron kinematics.
0. 90=mcθ
Hard photodisintegration of a proton pair
18
Experimental setup
e¡
Jefferson Lab
0.8-6 GeV
A
CB
Experiment E03-101
Hard photodisintegration of a proton pair
19
Experimental setup
Beam line
HRSHRS
Experimental Hall A
Experiment E03-101
Hard photodisintegration of a proton pair
20
Experimental setup
Electrons 3He cryotarget
Radiator
Photons
Target Chamber
Copper foils 1-6% r.l
Experiment E03-101
µ
Backgrounds are subtracted by “radiator out” and empty target runs
Build in quality-control – empty region beyond the endpoint
Beam energy
[GeV] γE
Radiator in
Radiator out
counts
With radiator
No radiator
Neutron momentum distribution based on 3He Wave function of R. Schiavilla, et al., PRL. 98, 132501 (2007), and references therein.
Correcting for the finite acceptance of the second spectrometer
Simulation assumes photon energy distribution based on Matthews and Owens NIM 111, 157-168 (73).
3He
p
pn
p
p
simulation
data
GeV 7.1=γE
Momentum of the proton [MeV/c]
Momentum of the proton [MeV/c]
HRS_right HRS_left
HRS_right HRS_left
angle of the proton [Deg.]
angle of the proton [Deg.]
Momentum of the neutron [MeV/c]
[Mev] γE
nα
Target position
[mm]
MC 2.1%
DATA 2.9%
Δ/D=-37%
MC 5.4%DATA 6.4%Δ/D=-19%
MC 16.3%DATA 16.6%Δ/D=-1.5%
MC 19.7%DATA 18.8%Δ/D=5%
MC 13.6%DATA 11.9%Δ/D=13%
MC 8.6%DATA 10.9%Δ/D=-28%
MC 5.9%DATA 5.1%Δ/D=12.5%
MC 13.5%DATA 15.3%Δ/D=-13%
MC 13.6%DATA 11.9%Δ/D=12.5%
MC 100%
DATA 100%
Box number
GeVE 7.1=γ
We (temporarily) assigned an extrapolation error of 15% to the data
At low photon energy
% 1 pn) ( / pp) ( 33 ≈→→ HeHe γσγσpn γγ σσ <<ppGeV/c 0.5 E ≤γFor
Laget NP A497 (89) 391, (Saclay data).
Magnitude of pp vs. pn hard photodisintegration
γ
ρπ ,0p
p
p
p
MEC is the dominant process
pp pair : only a neutral pion can be exchanged, its coupling to the photon is weak.
0 ≈ppγσ
Expected Results
Normalized to deuteron Absolute for 3He
Expected Results
See M. Sargsian talk
Expected Results
In contrast to low energy observations, nonperturbative models predict a large cross
section for the pp break up.
What are the relevant degrees of freedom?
This is an indication for quark – gluon dynamicsThe exchange particles in the diproton photodisintegration reaction are: Neutral at low energies where meson exchange dominates. Charged at high energy where quark exchanges dominate.
γE
?1
10
pn / σσ pp
The energy dependence of the pp/pn break up can map the transition
from hadronic to quark – gluon domain
preli
mina
ry
The new data were normalized to the preliminary CLAS data !
Preliminary Results
Δ(1
620)
S31
, N
*(16
50)S
11N
*(16
75)D
15,
N*(
1680
)F15
Δ(1
230)
preli
minary
preli
mina
ry
The new data were normalized to the preliminary CLAS data !
Preliminary Results
Δ(1
620)
S31
, N
*(16
50)S
11N
*(16
75)D
15,
N*(
1680
)F15
Δ(1
230)
200 )5.4( /)5.2( ≈dtd
dtd σσ
Δ(1230)
preli
mina
ry
Preliminary Results
Δ(1
62
0)S
31
, N
*(1
65
0)S
11
N*(
16
75
)D1
5,
N*(
16
80
)F1
5
Δ(1
23
0)
Δ(1
23
0)
N*(
15
20)
Preliminary Results
Outlook
?
?Improved statistic
Breaking a transverse compact object formed before the absorption?
) GeV/c 2 p ( ≈dψDouble hard scattering?
) MeV/c 300 P ( ≤dψ
RNA
HRM
We can utilize the recoil neutron to study how such large transverse- momentum nucleons are produced .
α=( E - PZ) / m
nppHeαααααγ ++=+=+
213 30
213 n pp ααα −−=⇒
Outlook
Physics Letters B 578 (2004) 69–77
n
p
p
p
p
n
γ
γ
αn 1
αn 1
scalingVerify the scaling for another hard exclusive reaction
Extend the verification of photodisintegrartion scaling
5
11
4
11
10 )1(
)5( 10
)1(
)4( ≈
⎥⎥⎦
⎤
⎢⎢⎣
⎡
==
≈⎥⎥⎦
⎤
⎢⎢⎣
⎡
==
γ
γ
γ
γ
EsEs
EsEs
Utilize the recoil neutron to study scaling
nppHeαααααγ ++=+=+
213 30
213 n pp ααα −−=⇒
2dd M
2
3M E 2 +
−≈ n
ppsα
γ
α=( E - PZ) / m
±3%
±1 S n-
)(
∝→ ppppdt
dγ
σ
HRM, α(1-1.2) / α(0.8-1)
Outlook
energy oscillation
If HRM is valid (see Sargsian talk) and photodisintegration amplitude can be factorized
Hard photodisintegration data can
be related to NN scattering data
We also have data pp),( 12 γCOutlook
Acknowledgment
Physics Letters B 578 (2004) 69–77
“Hard Photodisintegration of a Proton Pair in 3He”
Brodsky, Frankfurt, Gilman, Hiller, Miller, Radyushkin, Piasetzky, Sargsian, Strikman
Hall A / JLab.
Spokespersons: R. Gilman, E. Piasetzky
Experiment E03-101 collaboration
Graduate student: Ishay Pomerantz (Tel Aviv University)
Theoretical support : M. Sargsian
3He
γ p
p
µµ
HRS
n
θ
3He
γ
p
pn
p
pµµ
HRS
HRS
High – energy photodisintegration of a proton pair in 3He
Step 1. MCEEP Randomly pick scattering angle for the first proton
Step 2. MCEEP Randomly pick photon energy [1] and neutron momentum [2]
Step 3. MCEEP Calculates momentum magnitude of the first proton and the momentum of the second proton
[1] MATTHEWS AND OWENS NIM 111, 157-168 (73) [2] R. Schiavilla, et al., Phys. Rev. Lett. 98, 132501 (2007), and references therein.
MC 2.1%
DATA 2.9%
Δ/D=-37%
MC 5.4%DATA 6.4%Δ/D=-19%
MC 16.3%DATA 16.6%Δ/D=-1.5%
MC 19.7%DATA 18.8%Δ/D=5%
MC 13.6%DATA 11.9%Δ/D=13%
MC 8.6%DATA 10.9%Δ/D=-28%
MC 5.9%DATA 5.1%Δ/D=12.5%
MC 5.4%DATA 6.4%Δ/D=-19%
MC 13.5%DATA 15.3%Δ/D=-13%
MC 13.6%DATA 11.9%Δ/D=12.5%
MC 100%
DATA 100%
Δ/D [%]
Box number
Box number
GeVE 7.1=γ
Hard photodisintegration of the deuteron has been extensively studied
What did we learn?
What are the current problems?
) ( ) ( tt phighnphighpd +→γ
=1/3
16 / ≈pnpp γγ σσ
])dt
d( /)
dt
d[( )F / (F / 2
nppnpnreduced
ppreducedpp
σσσσ γγ =
FF
FF
FF
FF
N1
N2
N1
N2reduced2
2N21
2N1 )(-tF )(-tF
dt
d
dt
d σσ∝
4 (-2) )F / (F dataG andG 22np M E =≈⇒
4 ratio) (charge )dt
d( /)
dt
d( 2 =≈pn
reducedppreduced
σσ
5 3
16
][
MeV/c 100p ][
pn)d (
pp) He (2
n2He
pp3
3
≈≈•≤
=→→
∫∫
pn
pp
dγ
γ
σσ
ψ
ψ
γσγσ
∫∫ ≤
2
n2He
pp
][
MeV/c 100p ][
3
dψ
ψ
Is it SRC ? Does this talk being given in the correct section?
Preliminary Results
p
n
dF (p)
F (n)
F (p)
F (n)
RNA (Reduced Nuclear Amplitude)
Experimental nucleon FF gluon exchanges within the nucleons
Neglect diagrams with gluon exchanges between the nucleons
Photon can interacts with any quarks
)(p
1 (n)F (p)F
)m-(s
1 2
2t
2222
dcmf
dt
d θσ∝
Brodsky , Hiller PRC 28, 475 (1983)
p
n
dF (p)
F (n)
F (p)
F (n)
TQC (Two - Quark Coupling)
gluon exchanges within the nucleons Experimental nucleon FF
Photon interacts with the exchange pair of quarks
)()(
1 (n)F (p)F
)m-(s
1 2
222
22d
cmfsdt
d θσΛ−
∝
Radyushkin
gluon exchanges between the nucleons neglected
p
n
d
HRM (Hard rescattering Model)
p) (2 lowdψ
qTγ
NNNNT →
Convolution of large angle pn scattering amplitude , hard photon – quark interaction vertex, and low momentum nuclear wave function
The pn scattering amplitude is obtained from large angle pn data
Frankfurt, Miller, Sargsian, Strikman PRL 84, 3045 (2000).
Quark – Gluon String model (QGS)
3 q exchange with an arbitrary number of gluon exchanges
Regge theory - nonlinear trajectory
Grishina et al. EUR. J. Phys. A 10, 355 (2000)