OLYMPUS эксперимент

С.Белостоцкий сессия 2010

OLYMPUSOLYMPUS экспериментэксперимент

В. АндреевС.Белостоцкий Д.ВеретенниковГ.ГавриловА.ИзотовА.КиселевП.КравченкоА.КрившичО.МиклухоЮ.Нарышкин

+Отд.трек.дет.

Born ep CROSS SECTION AND POLARIZATIONTRANSFR

2 2 2 2E M

2

Mott

2

r2 2 2

p

e

E

2

M

G (Q ) G (Q )

G (Q ) G (

d d 1,

d d (1 )

Q,

4M

1photon polarizati

Q )

on , 0 1.1 2(1 )tan ( / 2)

pk'pk

ek 'ek

q

pJ

eJ Unpolarized cross section



2 2 2 2E M

2

Mott

2

r2 2 2

p

e

E

2

M

G (Q ) G (Q )

G (Q ) G (

d d 1,

d d (1 )

Q,Q

4M

1, 0 1.

1 2(1 ) tan ( /

)

2)

photon polarization

pk'pk

ek 'ek

q

pJ


Proton magnetic form factor



2 2 2 2E M

2

Mott

2

r2 2 2

p

e

E

2

M

G (Q ) G (Q )

G (Q ) G (

d d 1,

d d (1 )

Q,Q

4M

1, 0 1.

1 2(1 ) tan ( /

)

2)

photon polarization

pk'pk

ek 'ek

q

pJ



2 2

2p E 22 2M

Untill recently it was commonly

accepted t

μ G (Q )1 at

hat

Q 10 GeV / cG (Q )



2 2 2 2E M

2

Mott

2

r2 2 2

p

e

E

2

M

G (Q ) G (Q )

G (Q ) G (

d d 1,

d d (1 )

Q,Q

4M

1, 0 1.

1 2(1 ) tan ( /

)

2)

photon polarization

pk'pk

ek 'ek

q

pJ



иными словами, распределения заряда и магнетизма в протонесовпадают вплоть до растояний порядка 0.065 fm-1 !!


Puzzle of Proton Form Factor RatioPuzzle of Proton Form Factor Ratio


Dramatic discrepancy between Rosenbluth and recoil polarization technique

Jefferson LabMeasurement of recoil proton polarization

Puzzle of Proton Form Factor RatioPuzzle of Proton Form Factor Ratio

2 2E2 2M

'e e

ep

G (Q )

G (Q )

E EPtan( / 2)

P 2M


Contribution of Two Photon Exchange Effects Contribution of Two Photon Exchange Effects ????

+ e,p bremschtr.


p bremm

2 2 2 * 2 *ep ep Born Born 2 e bremmM M 2e M Re M 2e M M


+ e,p bremschtr.


p bremm



p bremm


2 2 2 *Born Born e bremstr p bremstr

2 2 2 *Born Born e bremstr p brems2 t

*r

*2Re(M )

Re

M 2e M 2e R e(M M )

M 2e M 2e Re(M MM ) )(

Charge asymmetry

P.G. Blunden et al.,Phys. Rev. C 72, 034612 (2005)

+ e,p bremschtr.


Model dependent

OLYMPUSEbeam=2 GeVarea

Dec.2010


The OLYMPUS ExperimentThe OLYMPUS Experiment• Electrons/positrons (100mA) in multi-GeV storage ring DORIS at

DESY, Hamburg, Germany

• Unpolarized internal hydrogen target (like HERMES) 3 x 1015 at/cm2 @ 100 mA → L = 2x1033 / (cm2s)

• Measure elastic e+/e- proton scattering to 1% precision at 2 GeV energy with ε range from 0.4 to 1 at high Q2 ~ 2-3 (GeV/c)2 using the existing Bates Large Acceptance Spectrometer Toroid

• Experiment requires switching from e+ beam to e- beam on timescale of ≤ 1 day.

• Redundant monitoring of luminosity, pressure, temperature, flow, current measurements - small-angle elastic scattering at high ε and low Q2


Создана Коллаборация OLYMPUS; Разработан TDR , в котором обозначен материальный и интелектуальный вклад участников в эксперимент; ПИЯФ и DESY подписали MoU о проведении эксперимента и об обязательствах сторон ; Эксперимент оффициально одобрен Департаментом Энергии США с гарантией финансовой поддержки; Администрация ОФВЭ поддерживает эксперимент и выделяет средства на разработку и изготовление аппаратуры, являющейся материальным вкладом института; Администрация DESY поддерживает эксперимент и содействует его проведению.

Статус эксперимента и вклад ПИЯФ

Разработана и производится трековая система монитора светимости (7 модулей пропорциональныхкамер, XUV-плоскости, шаг 1мм, всего на 2 200 каналов) для ep-elastic монитора. Проп.камеры будут использоваться в комбинации с GEM дет.ПИЯФ является отвественным за Slow Control;ПИЯФ участвует в Monte-Carlo моделировании эксперимента и в обработке и анализе экспериментальных данных.


time-of-flight

scintillators

target

GEMtrackers

12deg luminosity

GEM+MWPC

magnet coils

drift chambers

Moller/Bhabh

luminosity calorimeters

DORISbeam

OLYMPUS Experiment OLYMPUS Experiment


ep – coincidences, tracking, TOF, Δp/p

12 deg Luminosity Monitor 12 deg Luminosity Monitor

3GEMs+3MWPCs left /right symmetricallocated between toroid coilsserious difficulties with lack of space3GEMs+3MWPCs MC-tracking simulation

PCOS readout


Target System Target System

DESY integration:Will be new vacuum segment.Valves controlled by DESY vacuum group.

Pumps and internal valves will be controlled by OLYMPUS

Target Beamline Target Beamline


Test Beam Time in 2011 Test Beam Time in 2011

• TOF bars (spares from OLYMPUS)• 3 Lumi GEM detectors• 2 MWPC (prototype)• 16 lead glass detectors (Bonn)

Installation week 12-18 January


Time lines

Done-DCs wiring and tests-Toroid powering, control field mapping-TOF scint. counters revised, checked -Target cell fabricated Well on track-DORIS beam e+ /e- test 2.-2.3 GeV-IP area preparation, target installation January 2011-In construction• GEM trackers• 12 deg lumi: GEM+MWPC• Möller/Bhabha lumi calo Test run start January 2011 Detector commissioning in parking position February 2011Detector commissioning in DORIS beam August 2011 Data taking 2012


BACKUP SLIDES

Richard Milner DESY April 6, 2009 20

Projected OLYMPUS uncertaintiesProjected OLYMPUS uncertainties

Richard Milner DESY April 6, 2009 21

•Target cell installed and aligned•Cold-head installed•Pumps and controllers connected•Vacuum gauges connected

Target System Target System

R. Beck, F. Brinker DESY MAC 2010

• Shipped without wires• Completely re-wired• Currently

– electronics assembly

Wire Chambers Wire Chambers


• Existing radiation hard PbF2 crystals

• Assembly and testing

Moller/Bhabha Luminosity Monitor Moller/Bhabha Luminosity Monitor


ep ep e pM e e

Radiative Corrections & TPE graphs

p bremm

2 22 2 * *ep ep e p Born e p Born 2 e p e bremmM e e M 2e e M Re M 2e e M M

Calculable standardradiative correction

Contribution from two photon exchange diagram not taken into account in traditional analysis may be an explanation

S.Belostotski Seminar HEPD, May 05 2009

Change sign

ELASTIC ep SCATTERING AMPLITUDE ,CROSS SECTION AND POLARIZATIONTRANSFR

2

rMott p

2 2 2 2

2

2 2 2 2M

e

E E MG (Q ) G (Q ) G (Qd d 1 Q

, ,d d (1 ) 4M

1, 0 1.

1 2(1 ) tan ( / 2

) G (Q )

)photon polarization

pk'pk

ek 'ek

q

pJ

eJ

2 2' 'e e e p p pM2 E

1M e u k u k G (Q ) G (Q )e u k i q u k

q

In plane wave Born (OPE) approximation e-p scattering invariant amplitud

e

pJeJ Using M one may calculate all necessary observables:

Unpolarized cross section

Spin transfer from longitudinally polarized electron to recoil proton

2 2E2 2M

'e e

ep

G

(

E Etan(

(Q )

G (Q 2)

P

P M

P

P

Longitudinal polarization component (along recoil proton momentum)

Transverse polarizationcomponent in scattering plane

perp. to recoil proton momentum

)

/ 2)

under study


Extraction of FFs from Unpolarized Elastic e-p ScatteringExtraction of FFs from Unpolarized Elastic e-p Scattering


3R

2

iqx 3

3R

0

22 22

2

2D

22D

D

e e d x8

sin qRG Q

G Q

e RdR2 q

, Q qQ

0.84Ge

Q

V

GDipole parametrization

with

By far not idealbut acceptableparameterization


Schedule for studies

• Operation at 2.3 GeV successfully tested in 2009/2010• Electron tests in February 2011 • First runs with test experiment in February 2011• Test runs without detector during two service weeks in April

and June 2011 ( ~ 48 hours each week )• Starting full operation with detector in August 2011• Detector commissioning and beam studies during service

weeks in September and October 2011 + parasitic running at 4.5 GeV ( w/o target )

• Possibilities for access and short tests on most Wednesdays

• 1 week commissioning in January 2012

6 shifts in 1 week

4 days

4 days

2 days

_______

12 days

Documents

OLYMPUS эксперимент