Photoreactions with tensor-polarized deuterium target at VEPP3 - - PowerPoint PPT Presentation

Photoreactions with tensor-polarized deuterium target at VEPP–3

I.A.Rachek

Budker Institute of Nuclear Physics, Novosibirsk, Russia

September 18, 2009 experimental approach two-body deuteron photodisintegration coherent pion photoproduction on the deuteron upgrade: almost-real photon tagging system

• charge pion photoproduction → next talk

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 1

Experimental SetUp Method

Method of Superthin Internal Target

conception – in BINP first use – in BINP: VEP–1, VEPP–2, VEPP–3 later – in many Laboratories:

electron storage rings: NIKHEF, Bates, HERA . . . ion rings: IUCF, CELCIUS, COSY . . .

allows to increase substantially the efficiency of utilization of target material and beam particles, thus making feasible measurements:

with exotic targets: polarized ones; of rare-isotopes, etc. with exotic beams: positrons, antiprotons, ions of isotopes etc. with slow or heavy or strong-ionizing reaction products.

review of the method: S.G. Popov, Internal targets in storage rings of charged particles, Yad.Fiz. 62(1999)291

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 2

Experimental SetUp Internal Polarized Target

Atomic Beam Source

Liquid He

Liquid Nitrogen

Turbo Pump

S1–S5 – sextupole magnets MFT, SFT – RF-transition units IT – inlet tube Flux of deuterium atoms 8 · 1016 at/sec Degree of tensor polarization > 98% Degree of vector polarization < 2%

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 3

Experimental SetUp Internal Polarized Target

Storage Cell

To BRP Liquid Nitrogen 13mm 40 cm 24mm From ABS covered by drifilm µ 30 m-thick aluminum foil

e-beam

Gain over a jet target: K = 1.1 (L/2)2 D2 s Tjet Tcell for our cell K ≈ 65 New problems: depolarization in atom-wall collisions depolarization by mag. field of e-beam aperture limitation Solutions: special wall coating – drifilm

• mag. field strength >> Hc = 117 Gs

local modification of VEPP–3 beam optics

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 4

Experimental SetUp VEPP–3 storage ring

VEPP–3

VEPP–3 parameters Electron energy E0 2 GeV Mean beam current I0 150 mA Energy spread ∆E/E 0.05% RF HV magnitude U72 0.8 MV revolution period T 248.14 ns bunch length σL 15 cm vertical beam size∗ σz 0.5 mm horizontal beam size∗ σx 2.0 mm

• vert. β-function∗

βz 2 m

• horiz. β-function∗

βx 6 m Injection beam energyEinj 350 MeV Injection rate ˙ Iinj 1.5·109 s−1

∗ parameters in the center of 2nd straight section

shift graph (beam current vs. time)

Internal Target Area

VEPP-3

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 5

Photodisintegration Introduction

two-body deuteron photodisintegration

Heavy hydrogen was chosen as the element first to be examined, because the diplon is the simplest of all nuclear systems and its properties are as important in nuclear theory as the hydrogen is in atomic theory.

• J. Chadwick and M. Goldhaber, Nature 134(1934)237.

d γ p n

two-body deuteron photodisintegration ✞ ✝ ☎ ✆

γ + d → p + n

T-matrix: n = 2 × 3 × 2 × 2 = 24

PC

− − → 12 complex amplitudes; in total 2n2 = 288 various observables, but only 2n − 1 = 23 are independent any such “set-of-23” must include tensor asymmetries.

• H. Arenh¨
• vel, W. Leidemann, E.L. Tomusiak, “Complete sets of polarization
• bservables in electromagnetic deuteron breakup”, FBS 28(2000)147.

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 6

Photodisintegration Overview of theoretical models

Theoretical models

H.A.Bethe & R.Peierls, “Quantum theory of the diplon”, Proc. Roy. Soc. A148(1935)146 . . . E1-multipole only, simplest NN-potential V (r) = −V0 δ(r): dσBP dΩ = e2 α2 (η − 1)3/2 η3 sin2 θ, σBP(ω) = 8π 3 e2 α2 (η − 1)3/2 η3 where η = Eγ/Eb , α = √MdEb, Eb = 2.224 MeV M.Schwamb and H. Arenh¨

• vel, Nucl. Phys. A690(2001)682
• M. Schwamb, habilitation thesis, Johannes Gutenberg-Universit¨

at at Mainz, 2006 coupled–channels approach: NN, N∆, πNN pion retardation in NN-potential and in MEC; mutual interactions between the involved three particles in the propagating πNN-system is taken into account nonperturbatively no free parameters with respect to deuteron photodisintegration, all parameters have been fitted in advance by considering other reactions.

π π π π π π π π π π π π ρ/ω ρ/ω ρ/ω π π ρ/ω

retarded

π π π

static

π π ρ/ω π

From static approach to meson retardation MEC.

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 7

Photodisintegration Cross section

Cross Section

in case of polarized spin-1 target and unpolarized photon beam: dσ dΩ = dσ0 dΩ ( 1 − r 3 4 PZ sin θH sin φH · T11(Eγ, θCM

p

) + r 1 2 PZZ »3 cos2 θH − 1 2 · T20(Eγ, θCM

p

) − r 3 8 sin 2θH cos φH · T21(Eγ, θCM

p

) + r 3 8 sin2 θH cos 2φH · T22(Eγ, θCM

p

) #) Pz = n+ − n− – degree of target vector polarization Pzz= 1 − 3 · n0 – degree of target tensor polarization n+, n−, n0 – population numbers for spin projections +1,

−1 and 0, respectively.

Surface of constant density ρ = 0.24fm−3 in deuteron

P

zz = -2

P

zz = +1 H I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 8

Photodisintegration Almost-real photon approach

Almost–real photon approach

Electro-disintegration

θ e θ

H

scattering plane kp k k kn θ q

ϕ

p

θn

• rientation

plane reaction plane

H

θe → 0 Q2 → 0 Photo-disintegration

, lab

θp

CM CM

θn

• rientation

kp

H

plane

γ

E θH

ϕH

kγ kn reaction plane

for θe ≈ 0 : T electro

2M

≈ T photo

2M

· „ 1 − ρL ρT « ρT = 1 2 ξ + η; ρL = ξ2; ξ = Q2 | q|2 ; η = tan2 θe 2 for small θe : ρL/ρT = » 1 − r r(1 − r/2) · θe –2 , where r = Eγ/Ee.

e.g. for θcut

e

= 1◦ and Eγ/Ee = 0.1 δT2M/T2M ≤ 10−3

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 9

Photodisintegration Particle Detector

Detector Layout

• 2 pairs of arms in vertical

plane: arm I II θp 20◦-40◦ 55◦-95◦ θn 127◦-145◦ 68◦-92◦ ∆φ 25◦ 19◦

• proton arm:

drift chambers + 3 scintillator layers

• neutron arm:

thin veto-counter + thick scintillator Neutron arm #1 e Neutron arm #2

veto counters

e-arm of LQ-polarimeter

storage cell vertex chamber drift chamber DC2 scintillator 23.5x50x2 cm scintillator 27.5x50x12 cm scintillator 35x50x12 cm

drift chamber DC1

Proton arm #2 Proton arm #1

3 3 3 I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 10

Photodisintegration Particle Detector

neutron arms

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 11

Photodisintegration Separation of tensor observables

Separation of TIM

Tensor asymmetry:

aT = √ 2

σ+−σ− P+

zzσ−−P− zz σ+ → c0T20 + c1T21 + c2T22

c0 (θH, φH), c1 (θH, φH), c2 (θH, φH)

• 1
• 0.75
• 0.5
• 0.25

0.25 0.5 0.75 1 0o 30o 60o 90o 120o 150o 180o

θH φH

• 1
• 0.75
• 0.5
• 0.25

0.25 0.5 0.75 1 0o 45o 90o 135o 180o 225o 270o 315o 360o

VEPP–3 (2003) φH = 180◦θH = 180◦ a0 ∼ c0T20 θH = 54.7◦ a1 ∼ +c1T21 + c2T22 θH = 125.3◦ a2 ∼ −c1T21 + c2T22 → T20 ∼ a0 T21 ∼ a1 − a2 T22 ∼ a1 + a2 regime 0 regime 1 regime 2

kγ H kγ

54.7o

H kγ

125.3 o

H

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 12

Photodisintegration The Run

Data taking run

4-month run: Oct-2002 – Jan-2003 electron energy 2000 MeV, mean beam current 80 mA, total beam integral 200 KCoulomb target thickness 3 × 1013 at/cm2 target polarization measured by the LQ-polarimeter: Pzz = 0.341 ± 0.025 ± 0.013 raw events collected: 37.5M selected PD events: 540K beam integral vs. time

regime 0 62.3 kC regime 1 64.8 kC regime 2 71.7 kC 25 50 75 100 125 150 175 200

• 3
• 2
• 1

1

DEC-2002 JAN-2003 NOV-2002 OCT-2002

beam current integral [KCoulomb]

event distributions: . . . vs. photon energy

Eγ, MeV events per 5MeV

ARM2 (Θp=60o...95o) ARM1 (Θp=20o...40o) 10 2 10 3 10 4 50 100 150 200 250 300 350 400 450 500

. . . vs. proton angle

θp events per 1o cm

ARM1 ARM2

5000 10000 15000 20000 25000 20o 30o 40o 50o 60o 70o 80o 90o 100o 110o

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 13

Photodisintegration Comparison to calculations

Results: as a function of Eγ

• 1
• 0.75
• 0.5
• 0.25
• 0.5

0.5 1

T20 θcm = 24o - 48o θP T21 Eγ, MeV T22

• 0.5

0.5 100 200 300 400 500 600 0.2 0.4 0.6 0.8 1 0.2 0.4 0.6 0.8

T20 θcm = 70o - 102o θP T21 Eγ, MeV T22

• 1.5
• 1
• 0.5

100 200 300 400 500 600

vertical bars – statistic errors horizontal bars – bin sizes shaded bands – systematic errors

Theoretical curves:

solid – K.-M.Schmitt&H.Arenh¨

• vel

(1990), full calculation; dotted – M.Levchuk (1995), full calculation; dashed – M.Schwamb (2006).

I.A. Rachek et al., Phys.Rev.Lett 98 (2007)182303

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 14

Photodisintegration Comparison to calculations

ingredients of the model: from M.Levchuk

c a b d

PWIA FSI MEC FSI MEC

Eγ MeV T20 θcm = 70o - 102o θP

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 20 40 60 80 100 120 140 160 180

Eγ MeV T21 θcm = 24o - 48o θP

• 0.2

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20 40 60 80 100 120 140 160 180

Eγ MeV T22 θcm = 70o - 102o θP

• 2
• 1.75
• 1.5
• 1.25
• 1
• 0.75
• 0.5
• 0.25

0.25 0.5 20 40 60 80 100 120 140 160 180

(a+b) (a) (a+b+c+d)

Plane Wave Impulse Approximation PWIA+ Final State Interaction PWIA+FSI+ Meson Exchange Currents

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 15

Photodisintegration Comparison to calculations

Results: as a function of θcm

p ,

Eγ = 25 ÷ 140 MeV

• 1
• 0.5

0.5

• 0.5

0.5 1

Eγ= 25 - 45 MeV T20 T21 θp . T22

cm .

• 1
• 0.5

0.5 1 20o 30o 40o 50o 60o 70o 80o 90o 100o 110o

• 1
• 0.5

0.5

• 0.5

0.5 1

Eγ= 45 - 70 MeV T20 T21 θp . T22

cm .

• 1
• 0.5

0.5 20o 30o 40o 50o 60o 70o 80o 90o 100o 110o

• 1

1

• 1
• 0.5

0.5 1 1.5

Eγ= 70 - 100 MeV T20 T21 θp . T22

cm .

• 1.5
• 1
• 0.5

0.5 20o 30o 40o 50o 60o 70o 80o 90o 100o 110o

• 1

1

• 0.5

0.5 1 1.5

Eγ= 100 - 140 MeV T20 T21 θp . T22

cm .

• 1.5
• 1
• 0.5

0.5 20o 30o 40o 50o 60o 70o 80o 90o 100o 110o

I.A. Rachek et al., Phys.Rev.Lett 98 (2007)182303

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 16

Photodisintegration Comparison to calculations

Results: as a function of θcm

p ,

Eγ = 140 ÷ 440 MeV

• 1

1

• 1

1

Eγ= 140 - 180 MeV T20 T21 θp . T22

cm .

• 1.5
• 1
• 0.5

0.5 20o 30o 40o 50o 60o 70o 80o 90o 100o 110o

• 1
• 0.5

0.5 1

• 1

1

Eγ= 180 - 230 MeV T20 T21 θp . T22

cm .

• 1

20o 30o 40o 50o 60o 70o 80o 90o 100o 110o

• 1
• 0.5

0.5 1 1

Eγ= 230 - 330 MeV T20 T21 θp . T22

cm .

• 1

20o 30o 40o 50o 60o 70o 80o 90o 100o 110o

• 1
• 0.5

0.5 1

• 1

1

Eγ= 330 - 440 MeV T20 T21 θp . T22

cm .

• 2
• 1

1 20o 30o 40o 50o 60o 70o 80o 90o 100o 110o

I.A. Rachek et al., Phys.Rev.Lett 98 (2007)182303

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 17

Photodisintegration Comparison to calculations

Bonn (1989) tensor observable: Z–asymmetry

Z= √ 2T20 + √ 3T22 Eγ= 450 MeV θp Z cm

• 2
• 1

1 2 3 4 5 6 7 00 20o 40o 60o 80o 100o

data:

Bonn [Z. Phys. C43, 375 (1989)];

• Novosibirsk [2007]

curves: M.Schwamb&H.Arenh¨

• vel, K.-M.Schmitt&H.Arenh¨
• vel.

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 18

Photodisintegration Summary

Summary

New measurement of tensor analyzing powers T20, T21 and T22 in deuteron photodisintegration, substantially enhancing the quality and kinematic span of the existing experimental data, has been performed. Accuracy of our data allow an accurate test of available models in a energy range Eγ 400 MeV; Theoretical calculations provide excellent description of these polarization data below pion production threshold; Meson Exchange Currents play crucial role starting already at small photon energy; Above pion production threshold a very good description of T20 and T22 is demonstrated by a novel approach incorporating a π-MEC retardation mechanism the shape of angular dependencies of TIM is described well and here better agreement is observed for Schwamb model as well; The remaining discrepancies could reflect the theoretical uncertainties or some missing or poorly modeled underlying dynamics, so further improvement in theoretical models would be desirable.

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 19

Coherent Pion Photoproduction Introduction

Coherent Neutral Pion Photoproduction on Deuteron γ + d → π0 + d

the only pion photoproduction reaction on deuteron with two-body final state. issues addressed: deuteron structure π0 – deuteron elastic scattering pion photoproduction off neutron at threshold – chiral dynamics on neutron . . .

P.Wilhelm and H.Arenh¨

• vel,
• Nucl. Phys. A609(1996)469

– couple-channel approach: NN, Nπ, N∆

∆∆ R d d γ π 0 T

+

∆N R d d γ π 0 T

π 0 d d T γ

π 0

= d

d T γ

+

∆[2] d d γ π 0 j∆N[2] N[2] d d γ π 0 j

RN[2] d γ j

d π 0 T

+

d γ j∆N[2] d π 0 T

∆ R [2]

+ + +

S.S.Kamalov, L.Tiator and C.Bennhold, Phys.Rev. C55(1997)98 with FSI treated in the KMT multiple scattering approach

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 20

Coherent Pion Photoproduction Detector layout

Detector Layout for coherent π0 photoproduction

γ + d → π0 + d′ events have been selected from the statistics collected during the deuteron photodisintegration experiment. Data of one pair of arms used proton arm #1 detects deuteron neutron arm #1 detects

• ne of γ-quantum from

pion decay. θd 20◦ ÷ 40◦ ∆φ 25◦ Ed 20 ÷ 70 MeV

γ

d

Neutron arm #1 e Proton arm #1 Proton arm #2 Neutron arm #2 e-arm of LQ-polarimeter

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 21

Coherent Pion Photoproduction Background

Background processes

Processes that may give (dγ) coincidence in the detector: γd → d′π0π0 γd → d′η γd → d′π0π+π− taking into account available cross section data as well as theoretical predictions

• ne can conclude that process

process γd → d′π0 dominates and contribution of background processes does not exceed 2%

comparison of our data and GEANT4 simulation based on TAPS cross section data

Eγ, MeV events per 5MeV

data geant4 100 200 300 400 500 600 700 800 200 250 300 350 400 450

θπ events per 0.5o cm

data geant4 50 100 150 200 250 300 350 400 450 500 80o 90o 100o 110o 120o 130o 140o 150o I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 22

Coherent Pion Photoproduction Results

Results on coherent π0 photoproduction

• vs. Eγ
• 1
• 0.5

0.5

• 1.5
• 1
• 0.5

0.5

T20 θcm = 90o - 145o θπ

Fix, et al Kamalov, et al

T21 Eγ, MeV T22

• 0.5

0.5 200 250 300 350 400 450

• vs. θcm

π

• 1
• 0.5

0.5

• 1
• 0.5

T20 Eγ = 250 - 450 MeV

Fix, et al Kamalov, et al

T21 θπ T22 cm

• 0.5

0.5 90o 100o 110o 120o 130o 140o 150o

Vertical bars – statistical errors, Horizontal bars – bin sizes; Systematic error ≈ 9.4%

Theoretical curves:

solid – A.Fix, private communication, dashed – S.S.Kamalov, L.Tiator and C.Bennhold, Phys. Rev. C 55(1997)98 D.M.Nikolenko, L.M. Barkov et al., JETP Lett. 89, 518 (2009)

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 23

Coherent Pion Photoproduction Proposed experiment

Proposed experiment

plastic electron beam LQP Target chambers

Pi−0 arm Deuteron arm

wire scintillators CsI(Tl)

Veto Counters

θγ1 θγ2 2

γ

θπ 1

γ

2

γ θd γ d

• π

γ1

γ + π d d +

• +

segmented calorimeter of 152 CsI(Tl) crystals 6 × 6 × 15cm3 to measure both γ-quanta → full kinematic reconstruction Eγ = 250 ÷ 450 MeV Ed = 25 ÷ 120 MeV θd = 18◦ ÷ 35◦ θCM

π0 = 100◦ ÷ 140◦

∆φd, ∆φπ◦ ≈ 60◦

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 24

Coherent Pion Photoproduction Expected accuracy of the T20 measurement

Expected accuracy

Statistical accuracy for 100 kCoulomb beam integral (≈ 2 month run at VEPP–3)

• 1
• 0.8
• 0.6
• 0.4
• 0.2

0.2 90o 105o 120o 135o 150o 165o 180o

• 1
• 0.8
• 0.6
• 0.4
• 0.2

0.2 90o 105o 120o 135o 150o 165o 180o

Coherent πo photoproduction on the deuteron Θπo T20

Eγ = 260 MeV

Θπo

Eγ = 340 MeV

S.S.Kamalov et al. P.Wilhelm and H.Arenhoevel

Θπo

Eγ = 400 MeV

• 1
• 0.8
• 0.6
• 0.4
• 0.2

0.2 90o 105o 120o 135o 150o 165o 180o I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 25

Almost–real photon tagger Introduction

Almost–real photon tagger

Introduction of almost–real photon tagging system would allow a complete kinematic reconstruction, thus permitting a reliable rejection of the background processes to extend the measurements to higher photon energy; to determine the linear polarization of photon, thus enabling Σ–asymmetry measurements and double–polarization experiments

linear polarization of almost–real photon vs. its energy

Photon to electron energy ratio 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Polarization 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

2000 1600 1200 800 400

E γ MeV ,

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 26

Almost–real photon tagger VEPP–3 experimental section

Layout of the Tagging System at the experimental section

CP

HF HF

CP SM

DS1

QD

DS2

ABS QF CP

3.14kGm

D3

2.48kGm

D2 D1

GP SC

BRP

2 GeV e beam 0.5 m 5.62 kGm C2

1 GeV E e = . 5 G e V

C1

Top view at the experimental section of VEPP–3 with the chicane and the scattered electron tracker installed.

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 27

Almost–real photon tagger Experimental resolutions (simulation)

Tagger: expected energy and angular resolutions

Eγ = (0.50 ÷ 0.75)Ee

δEγ Eγ = 1.4% . . . 0.3%

αhoriz = −30 ÷ +30 mr δαhoriz = 2 mr αvert = −10 ÷ +10 mr δαvert = 1 mr contributions to resolution at Ee = 2GeV

X1, mm

• 40
• 20

20 40 60 80 100

X2, mm

• 50

50 100 150 200 1000 MeV 800 MeV 900 MeV 700 MeV 600 MeV 500 MeV

Electron Energy, MeV

500 550 600 650 700 750 800 850 900 950 1000

Energy Resolution, MeV

2 4 6 8 10 12 14

Calculation X_1 ∆ X_2 ∆ Scattering X_Beam ∆ Z ∆ Total

Electron Energy, MeV

500 550 600 650 700 750 800 850 900 950 1000

Angle Resolution, mrad

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Calculation X_1 ∆ X_2 ∆ Scattering X_Beam ∆ Z ∆ Total Electron Energy, MeV

500 550 600 650 700 750 800 850 900 950 1000

Vertical Angle Resolution, mrad

0.5 1 1.5 2 2.5 X1, X2 S T

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 28

Almost–real photon tagger Example of experiment

Example of experiment: deuteron photodisintegration at Eγ =1.0÷1.5 GeV transition from meson-baryon to quark-gluon picture of deuteron ?

pQCD: Constituent Counting Rule, Hadron Helicity Conservation: dσ/ds → s−11 py, c′

x, c′ z → 0

Σ → −1 T20 → − √ 2, T21,T22 → 0 experimental results for photodisintegration at θcm

p

= 90◦:

cross section shows pQCD scaling above Eγ ≈ 1 GeV induced proton polarization vanishes at Eγ ≈ 1 GeV as HHC predicts but Σ asymmetry heads away from HHC at Eγ = 1 ÷ 1.5 GeV

cross section → s−11 induced polarization → 0 T20 → − √ 2 ?, T21,T22 → 0 ? Σ asymmetry → −1 ?

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 29

Almost–real photon tagger New detector

Proposed detector layout

Eγ = 1000 ÷ 1500 MeV Ep = 500 ÷ 1000 MeV En = 500 ÷ 1000 MeV θp = 45◦ ÷ 85◦ θCM

p

= 70◦ ÷ 110◦ ∆φp, ∆φn ≈ 2 × 60◦

hadron sandwich

10 layers × (20mm Iron + 5+5mm Scintillator) 10 cm segmentation in both directions WLS fibers readout

[G.I. Britvich et al., NIM A564(2006)225]

neutron detection efficiency: 60 . . . 70% angular resolution for neutrons 1.6◦

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 30

Almost–real photon tagger Expected accuracy

Expected accuracy

Expected accuracy for a 4 month run at VEPP-3

Eγ, MeV T20

γ + d → p + n θcm = 90o θP

HHC

• 2
• 1.5
• 1
• 0.5

0.5 1 200 400 600 800 1000 1200 1400 1600

PRL 98 (2007) 182303;

• Proposed experiment

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 31

Collaboration Participants

Participants Novosibirsk Electron-Deuteron Collaboration

L.M. Barkov, V.F. Dmitriev, I.V. Karnakov, B.A. Lazarenko, S.I. Mishnev, D.M. Nikolenko, I.A. Rachek, R.Sh. Sadykov, Yu.V. Shestakov, D.K. Toporkov, L.I. Shekhtman and S.A. Zevakov BINP, Novosibirsk, Russia A.Yu. Loginov, A.N. Osipov, A.A. Sidorov and V.N. Stibunov INR, Tomsk, Russia R.J. Holt, D.H. Potterveld ANL, Argonne, IL, USA

• R. Gilman

Rutgers University, Piscataway, NJ, USA

• H. de Vries

NIKHEF, Amsterdam, The Netherlands S.L. Belostotsky, V.V. Nelyubin INP, St.-Petersburg, Russia

• H. Arenh¨
• vel

IKP, Johannes Gutenberg-Universit¨ at, Mainz, Germany

I.A.Rachek Photoreactions with tensor-polarized deuterium target at VEPP–3 September 18, 2009 32