Double Deeply Virtual Compton Scattering Opportunities in Hall
Double Deeply Virtual Compton Scattering Opportunities in Hall A at Jefferson Laboratory Alexandre Camsonne ECT* Trento workshop October 24 th to 28 th 2016 Jefferson Laboratory Hall A
DVCS / Double DVCS g* + p g‘(*) + p’ l+ + l- Guidal and Vanderhaegen : Double deeply virtual Compton scattering off the nucleon (ar. Xiv: hep-ph/0208275 v 1 30 Aug 2002) Belitsky Radyushkin : Unraveling hadron structure with generalized parton distributions (ar. Xiv: hep-ph/0504030 v 3 27 Jun 2005) 9/15/2016 2
DDVCS cross section • VGG model • Order of ~0. 1 pb = 10 -36 cm 2 • About 100 to 1000 smaller than DVCS • Virtual Beth and Heitler • Interference term enhanced by BH • Contributions from mesons small when far from meson mass 9/15/2016 3
Double Deeply Virtual Compton Scattering p = p 1+p 2 q = ½ (q 1+q 2) D = p 1 -p 2 = q 2 -q 1 Q 2 = - q 2 Q 2 D. q x= h= 2 p. q scattered proton Q 2= -(k-k’)2 x = Q 2 bj 2 p 1 q 1 scattered electron outgoing virtual photon 9/15/2016 lepton pair from virtual photon Belitsky Radyushkin : Unraveling hadron structure with generalized parton distributions (ar. Xiv: hepph/0504030 v 3 27 Jun 2005) 4
Kinematical coverage JLab 11 Ge. V 25 Ge. V 40 Ge. V DVCS h=x Hu(h , x) 2 2 • DVCS only probes h = x line • Example with model of GPD H for up quark • Jlab : Q 2>0 h x 9/15/2016 • Kinematical range increases with beam energy ( larger dilepton mass ) 5
Two letters of intent at JLab • PAC 43 : Measurement of Double Deeply Virtual Compton Scattering (DDVCS) in the dimuon channel with the So. LID spectrometer (Boer, Camsonne, Gnanvo, Sparveri, Voutier, Zhao) • PAC 44 : Electroproduction of muon pairs with CLAS 12: Double DVCS and J/ψ electroproduction (Boer, Guidal, Stepanyan, Guidal, Paremuzyan) 9/15/2016 6
LOI 12 -15 -005 Measurement of Double Deeply Virtual Compton Scattering (DDVCS) in the di-muon channel with the So. LID spectrometer H. Atac 4, W. Armstrong 15, V. Bellini 10, A. Blomberg 4, M. Boer 5, A. Camsonne 1, G. Charles 2, J. -P. Chen 1, E. Cisbani 8, M. Defurne 12, R. Dupré 2, S. Covrig 1, K. Gnanvo 6, C. Gu 6, P. Guèye 14, M. Guidal 2, T. Hemmick 16, M. K. Jones 1, S. Joosten 4, C. Le Galliard 2, N. Linayage 6, D. Marchand 2, M. Mazouz 13, Z. -E. Meziani 4, P. Moran 4, H. Moutarde 12, C. Muñoz Camacho 2, S. Niccolai 2, M. Paolone 4, F. Sabatié 12, N. Sparveris 4, C. M. Sutera 10, A. W. Thomas 11, G. M. Urcioli 9, E. Voutier 2, Z. Zhao 3, Z. Ye 7 Jefferson Lab, Newport News, VA, USA 2 IPN, Orsay, France 3 Old Dominion University, Norfolk, VA, USA 4 Temple University, Philadelphia, VA, USA 5 Los Alamos National Laboratory, Los Alamos, NM, USA 6 University of Virginia, Charlottesville, VA, USA 7 Duke University, Durham, NC, USA 8 Istituto Superiore di Sanità, Roma, Italia 9 INFN, Roma, Italia 10 Università di Catania, Italia 11 ARC, Adelaïde, Australia 12 CEA Saclay, Gif-sur-Yvette, France 13 Faculté des Sciences, Monastir, Tunisia 14 Hampton University, Hampton, VA, USA 15 Argonne National Laboratory, Argonne, IL, USA 16 Stony Brook University, Stony Brook, IL, USA 1 Newport News, May 6 -7, 2016 3/…
Muon detection @ So. LID 3/31
DDVCS Ideally want Q’ 2 to be high enough to be away from pion production and have Q’ 2 < Q 2 Dedicated experiment Parasitic experiment first exploratory measurement Need luminosity and improved Q’ 2 and Q 2 coverage hence So. LID Newport News, May 6 -7, 2016 7/…
DDVCS v Cross sections, calculated within the twist-2 VGG approach, are about two orders of magnitude smaller than DVCS. |BH 1+BH 2+DDVCS|2 v Additional Bethe-Heitler like |BH 1+BH 2|2 |DDVCS|2 Newport News, May 6 -7, 2016 contributions with different f-dependence interfere with the pure small DDVCS amplitude. v Muon pair detection in the final state allows to circumvent electron indiscernability. 8/…
DDVCS |BH 1+BH 2+DDVCS|2 |BH 1+BH 2|2 Newport News, May 6 -7, 2016 The BSA of the DDVCS process allows to access the same linear combination of the Compton form factors than the BSA of DVCS, however at h≠x. 9/…
Muon detection @ So. LID 3/31
Muon detection @ So. LID Preliminary design from IPNO : Christine Legalliard / Dominique Marchand /Eric Voutier start to interact with So. LID Hall A designer Need to figure cable management and interference with End Cap motion Very rough estimate : 200 K$ to 500 K$ 3/31
DDVCS @ So. LID Acceptance 1 st FAMD (P>0. 7 Ge. V) 2 nd FAMD (P>1 Ge. V) 3 rd FAMD (P>1. 5 Ge. V) 4 th FAMD (P>2 Ge. V) 1 st LAMD (P>1 Ge. V) 3/31
DDVCS @ So. LID Detector acceptance 3/31
DDVCS @ So. LID Kinematical coverage 3/31
DDVCS @ So. LID Muon Discrimination 3/31
ele Trigger at EC e- with Q 2>1 • • e- with Q 2>1 Jpsi and TCS ele trigger (red): by FAEC with 4 Ge. V (r=105 -115 cm), 3 Ge. V (r=115145 cm) and 2 Ge. V (r=145 -235 cm), by LAEC with 3 Ge. V (r=80 -100 cm) and 2 Ge. V (r=100 -140 cm) DDVCS ele trigger on Q 2=1 (blue): by FAEC with 4 Ge. V (r=105 -115 cm), 3 Ge. V (r=115 -145 cm) and 1 Ge. V (r=145 -235 cm), by LAEC with 1 Ge. V (r=80 -100 cm) and 0. 5 Ge. V (r=100 -140 cm) (as we don't have 0. 5 Ge. V trigger curve for now, use 1 Ge. V curve instead)
Muon trigger rate • • • Muon Trigger (2 nd FAMD+1 st LAMD)2 (((161+284+505+869)+(230+162+102+144))*1 e 3)^2*30 e-9/1 e 3=181 k. Hz Muon Trigger (2 nd FAMD)2 ((161+284+505+869)*1 e 3)^2*30 e-9/1 e 3=100 k. Hz Muon Trigger (3 rd FAMD+1 st LAMD)2 (((17+29+213+379)+(230+162+102+144))*1 e 3)^2*30 e-9/1 e 3=49 k. Hz Muon Trigger (3 rd FAMD)2 Use “Hall. D” pion generator instead of ((17+29+213+379)*1 e 3)^2*30 e-9/1 e 3=12 k. Hz “Wiser” Muon Trigger (4 th FAMD+1 st LAMD)2 (((4+5+90+157)+(230+162+102+144))*1 e 3)^2*30 e-9/1 e 3=24 k. Hz Muon Trigger (4 th FAMD)2 1 st LAMD is before LGC, 2 nd LAMD is previous 1 st LAMD ((4+5+90+157)*1 e 3)^2*30 e-9/1 e 3=2 k. Hz Simulation JLAB_VERSION 1. 3 instead of 1. 2
DDVCS @ So. LID Random coincidence background • At 4 th FAMD, pip(2. 2 k. Hz), pim(0. 26 k. Hz), Time resolution 1 ns, 6 muonp(7. 4 k. Hz), muonm(7. 0 k. Hz) sigma cut is 6 ns • Two hadron 6 ns time coincidence Vertex resolution 0. 75 cm, (2. 2+7. 4)*1 e 3*(0. 26+7. 0)*1 e 3*6 e-9=0. 418 Hz 6 sigma cut 5 cm, factor 3 • Then hadron and ele 6 ns time coincidence reduction for 15 cm long (520)*1 e 3*(0. 418)*6 e-9=0. 0013 Hz target • Then vertex cut between 3 particles, Cut with P>2 Ge. V because BH muon has P>2 Ge. V at 0. 0013/3/3=0. 000145 Hz 4 th FAMD 3/31
DDVCS @ So. LID • BH signal 0. 126 Hz at 3 rd FAMD • Signal/(random coincidence background)=0. 126/0. 00762=17 • BH signal 0. 084 Hz at 4 th FAMD • Signal/(random coincidence background)=0. 084/0. 000145=579 3/31
DDVCS @ So. LID Expected Results 3/31
DDVCS @ So. LID Expected Results Two bins : 8 bins in Phi Q 2 > Q’ 2 : 2. 0 Ge. V 2< Q 2<2. 2 Ge. V 2 1. 9 Ge. V 2< Q 2<2. 1 Ge. V 2 Q 2 < Q’ 2 : 1. 6 Ge. V 2< Q 2<1. 8 Ge. V 2 1. 9 Ge. V 2< Q 2<2. 1 Ge. V 2 Asymmetries from 5 to 10 % 3/31
So. LID JPsi Setup Muon chambers Cernkov detectors Forward Iron plate Calorimeter Large Angle Calorimeter GEM trackers 9/15/2016 24
Counts J/psi setup 60 days at 10^37 cm-2 s-1 9/15/2016 25
Dedicated setup Iron plates • Target moved 2 m from Jpsi position inside and switch to 45 cm target • Iron plate from 3 rd layer yoke in front and behind calorimeter • Remove Gas Cerenkov • Try to reach 1038 cm-2 s-1 • 10 u. A on 45 cm target 9/15/2016 26
Expected accuracy dedicated setup 90 days at 1038 cm-2 s-1 9/15/2016 27
Eta and xi coverage 9/15/2016 28
Eta Xi coverage large bin 9/15/2016 29
Higher luminosity ? • Current could go up to 80 u. A • Target length up to 1 meter • Tracker occupancy and photon background – – – Reduce amount of Copper in GEM Micromegas option Build smaller chambers and add more channels Study complement with 2 D pad readout Superconducting tracker option • Calorimetry – Study liquid scintillator and cryogenics calorimeter option – Superconducting detector to replace PMT ( 1 ns width pulse to increase rate capability ) • Cerenkov – Superconducting detector to replace PMT ( 1 ns width pulse to increase rate capability ) – HBD type Cerenkov for Large Angle calorimeter 9/15/2016 6. 10^38 cm-2 s-1 Technically doable mostly matter of cost 30
Conclusion • Jlab 12 Ge. V beam along with high power target offers a unique opportunity to study DDVCS • Muon detection is interesting to distinguish from incoming electron and to increase luminosity • Hall B DDVCS or So. LID Parasitic measurement on J/Psi could give a first measurements of DDVCS • Dedicated setup could increase luminosity by a factor of 10 up to 1038 cm-2. s-1 for improved statistical accuracy • High statistics would allow binning in different variables to look a binning in Q’ 2 to probe xi eta surface with xi different of eta of GPDs 9/15/2016 31
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