np Charge Exchange Polarimetry in GeV Region

N. Piskunov

Measurement of analyzing powers for the reactionp + CH2 up to 7.5 GeV/c

and n + CH up to 4.5 GeV/c at the Nuclotron(ALPOM2 proposal)

V.P. Balandin, A.E. Baskakov, S.N. Basilev, K.S. Belova, Yu.P. Bushuev, O.P. Gavrishchuk, V.V. Glagolev, D.A. Kirillov, N.V. Kostayeva, A.D. Kovalenko, N.A. Kuzmin, A.N. Livanov,

I.A. Philippov, N.M. Piskunov, A.A. Povtoreiko, P.A. Rukoyatkin, R.A. Shindin, A.V. Shipunov, A.V. Shutov, I.M. Sitnik, V.M. Slepnev, I.V. Slepnev, S.Ya. Sychkov, A.V. Terletskiy,

A.I. YukaevJoint Institute for Nuclear Research, 141980 Dubna, Moscow region, Russia

C.F. Perdrisatthe College of William and Mary, Williamsburg, VA 23187, USA

V. PunjabiNorfolk State University, Norfolk, VA 23504, USA

M.K. JonesThomas Jefferson National Accelerator Facility, Newport News, VA 23606, USA

E. BrashChristopher Newport University and TJNAF

G. Martinska, J. UrbanUniversity of P.J. Šafarik, Jesenna. 5, SK-04154 Košice, Slovak Republic

J. MušinskyInstitute of Experimental Physics, Watsonova 47,SK-04001 Kosice, Slovak Republic

E. Tomasi-GustafssonIRFU, SPhn, CEA Saclay and IN2P3/IPN Orsay, France

D. Marchand, Y. WangIPN Orsay, 91406 ORSAY cedex, France

J. R.M. Annand, K. HamiltonUniversity of Glasgow, Glasgow G12 8QQ, Scotland, UK

ALPOM2 Collaboration

Current Status and Projected Errors for GEp/GMp and GEn/GMn

3

For recoil polarization, the two polarization components are in the reaction plane, no normal component:

Superior method: “ much smaller systematics”

Form Factor ratio is independent of the electron polarization Pe and of the polarimeter analyzing power Ay (h is beam helicity ±1).

2MG2

EGoIand2eθtanM2

)e'Ee(EP

tP

MpGEpG

-

Polarization transfer in or spin-target asymmetry (N=p or n), two different techniques, which give same information.

NeNe

Statistical uncertainty depends directly on both Pe and Ay.

,eNNe

Focal Plane Polarimeter

Ptfpp and Pn

fpp are the polarization components at the FPP

Front Trackers CH2 AnalyzerRear Trackers

Physical Asymmetries are obtained from difference distributions

2),(

2)ff(E ii

i

Sum distribution gives instrumental asymmetries

sinfpp

nPyAcosfpptPyA

2),(

2ifif

iD

sinfpp

nP)(yAcosfpptP)(yA1

2π)ε(θ,),(f

Azimuthal distribution of protons after scattering in the analyzer

E12-11-009

CH – material

Low detection efficiency

ALPOM

ALPOM2

CH2

CH2

p

p

Hadroncalorimeter

n (p) p (n)

2001

CH (CH2)

Proton polarimetry

p + C(CH2) -> charged particle + X

Neutron polarimetryn + p -> n + p , CH - target

New suggestion: n + p -> p + nCharge exchange reactionAerogel

counter

pp -> pppd -> pn + (p)

np -> pnPhys. Rev. Lett 30 (1973) 1183Phys. Rev. Lett 35 (1975) 632

decr

easing

with

ener

gy

incr

easing

with

ener

gy

The existing data for Ay in np elastic scattering indicate that the analyzing power decreases faster than the pp analyzing power, becoming very small, then negative around 6 GeV/c neutron momentum.

AyAy

0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5, 0 5,50,01

0,1

1

10

100

d/d

t, m

b/(G

eV/c

)2

-t, (GeV/c)2

0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0-0,9

-0,8

-0,7

-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0,0

0,1

0,2

0,3

Ay

-t, (GeV/c)2

3.6 GeV/c

3.0 GeV/c

np -> np np -> pn

dσ/dtel > dσ/dtce

| Ayel | < | Ay

ce |

FOMel < FOMce

and increasing with energy

Liquid H2 or D2 target

E12-11-009CH - target

(for proton as a target)From WangYing talk

Changing CH to CH2 increasesdifference FOM twice

0,0 0,5 1,0 1,5 2,0 2,5 3,00

50

100

150

200

250

300

ev

ents

Tkin, GeV

HBC, 3.83 GeV/c protons & pions

0,2 0,4 0,6 0,8 1,0

0

20

40

60

80

100

120

140

160

180

200

220

even

ts

= p/E

0,84 0,86 0,88 0,90 0,92 0,94 0,96 0,98 1,00

0

20

40

60

80

100

120

140

160

180

200

220

even

ts

= p/E

5933 protons5252 pions

Aerogel counter

Suppression of pionsemitted from the targetby aerogel counter

If we use this counter in the differential mode we can detect only protonsin our sensitive region

Thre

shol

d

upper

low

Schematic of Neutron Beam Extraction and Transport

Scheme of both extracted deuteron and free neutron beam lines. The beryllium target BT for the neutron production, the collimators C1 – C4, the monitors M1, M2 for estimation of beam intensity, the SM – magnet for vanishing of the charged deuterons.

neutron monitors

Neutrons have a laboratory momentum Pn = Pd /2 with a gaussian momentum spread of σP/P ~ 3 ÷ 4 %

The distance form the BT to the collimator exit is about 12 m and thus determining the solid angle equal ~ 5 msr.

Hadron calorimeter

Active targetFor neutron Aymeasurement

Neutron beam

Drift chambers

Aerogelcounter

Neutronbeam

Picture of the ALPOM2 Setup

Hadron calorimeter

Active targetFor neutron Aymeasurement

The angular distribution of charged particles after the target.

Theta-phi correlation plot.

MC simulation result

The angular distributions of neutrons and protons with the momentum of 3.75 GeV/c for CH and CH2 targets, compared with the distribution for incident protons.

0.0 0.2 0.4 0.6 0.8 1.0101

102

103

104

105

# e

vent

s

Pperp,GeV/c

p+CH2p+CHp+N

About 106 tracks

Conclusion

Thank you for your attention

Charge-exchange np reaction is preferable overnp elastic scattering in GeV region

A new polarized source is under testing

The setup has been tested

We hope that the measurements be done in 2016

0,0 0,2 0,4 0,6 0,8 1,0

0,1

1

10

p + CH2 3.8 GeV/c (2001) 3.75 GeV/c (2015)

rela

tive

units

pt , GeV/c

unscat tered beam

p + C scattering

p +N scattering

region sensitive for ana lyzing power

arXiv:1408.4928v1 [nucl-ex] 21 Aug 2014

np ->np

np ->pn

np ->np

np ->pn

1.1 GeV

np -> pnDelta-sigma setupCarbon contribution

0.8 GeV

1.4 GeV

1.05 GeVdp -> (pp) n

Strela setup

CH2C

0 5000 10000 15000 20000 250000

2x104

4x104

6x104

8x104

even

ts

cal.sum

1 -> 1 unsc. beam 1 -> 0 1 -> 2

0 5000 10000 15000 20000 250000

1x105

2x105

even

ts

cal.sum

0->1 0->0 0->2 +

10.3*10^6 trigs

0 10000 20000 30000 400000

20000

40000

B

cal.sum

1 -> 1 unsc. beam 1 -> 0 1 -> 2

3.75 GeV/c protons 6.0 GeV/c protons

3.75 GeV/c neutrons HBC, 3.83 GeV/cprotons & pions

A.Yu. Troyan

0,0 0,5 1,0 1,5 2,0 2,5 3,00

50

100

150

200

250

300

even

ts

Tkin, GeV

CH2 CH2

CH H2

0,2 0,4 0,6 0,8 1,0

0

20

40

60

80

100

120

140

160

180

200

220

even

ts

= p/E0,84 0,86 0,88 0,90 0,92 0,94 0,96 0,98 1,00

0

20

40

60

80

100

120

140

160

180

200

220

even

ts

= p/E

HBC, 3.83 GeV/cprotons & pions

5933 protons5252 pions

Aerogel counter

10o

~ 105 – 106

per cycle

40 cm3 - 4.5 GeV/c

1% per 1 cm,40% per 40 cm

Dead time of the data acquisition ~ 30 µs

5 * 105 2 * 105

(15-20) 103 events per second

We can take the data ~ 10 s

Really (now) ~ 3-4 s, so 7*104 events per cycleFor 5 cycles per min = 35*104

Elastic np cross section (<100) ~ 2 mbTotal (np+nC) ~ 350 mb

175*103 * 2 / 350 = 2000 np events per min

Half reaches hadcal, so 175*103 per min107 events per 1 hour

hadcal

Tn = 1.05 GeV/c

dp -> (pp) n

CH2C

p1 + p2 , GeV/c

Strela setup

30

2015-2016

Test the polarimeter using the polarized proton beam of 7.5 GeV/c 48 hours.

2016-2017

Total Data taking time 240 hours.

for proton beam 120 hoursa) measurement of Ay at proton momentum of 5.3 GeV/c (control point)b) two measurements to check polarization of breakup proton, at k=0.15 GeV/c with deuteron momentum of 11.2GeV/c (proton momentum 6.5 GeV/c) and at k = 0 GeV/c withdeuteron momentum of 13.0 GeV/c (proton momentum 6.5 GeV/c)c) measurement of Ay at proton momentum of 7.5 GeV/c

for neutron beam 120 hoursmeasurement Ay at neutron momenta of 3.0, 3.75 and 4.5 GeV

Beam Time Request

CH, 6x5 cmDeuterons7.5 GeV/cNeutrons

3.75 GeV/c

2.94 GeV/n15.06.1450

CH2, 20 cm40 cm,Empty

Deuterons7.5 GeV/c

2.94 GeV/n21.02.1449

CH2, 40 cmEmpty

Protons???

5.15 GeV/n13.12.1348

CH2, 40 cmEmpty

Protons

5.66 GeV/c

4.5 GeV/n

4.8 GeV/n

25.03.13

27.03.13

47

TargetBeam onthe target

Deuteronenergy

DateNuclotronrun

ALPOM2 setup