Tagged Deep Inelastic Scattering:

Tagged Deep Inelastic Scattering: Exploring the Meson Cloud of the Nucleon Dipangkar Dutta Mississippi State University Next generation nuclear physics with JLab12 and EIC FIU, Feb 10-13, 2016

Outline 1. Introduction - Mesonic content of nucleons 2. Tagged structure functions - Sullivan process and access to meson cloud of nucleon - New experiment at JLab12 3. Tagged DIS at an EIC 3. Summary Mississippi State U. D. Dutta FIU, February 2016 2 /33

Mississippi State U. D. Dutta FIU, February 2016 3 /33 There is ample evidence that nucleons have some mesonic content in them. Experimental evidence pointed to the nucleon existing ~20% of the time in a virtual meson-nucleon state.

There is ample evidence that nucleons have some mesonic content in them. Experimental evidence pointed to the nucleon existing ~20% of the time in a virtual meson-nucleon state. J. Arrington, arxiv 1208:4047 (2013) Pasquini and Boffi, Phys. Rev. D 76, 074011 (2007) Kelly, Phys. Rev. C 66, 065203 (2002) Proton & Neutron Charge Distribution Mississippi State U. D. Dutta FIU, February 2016 4 /33

There is ample evidence that nucleons have some mesonic content in them. Experimental evidence pointed to the nucleon existing ~20% of the time in a virtual meson-nucleon state. J. Arrington, arxiv 1208:4047 (2013) Pasquini and Boffi, Phys. Rev. D 76, 074011 (2007) Kelly, Phys. Rev. C 66, 065203 (2002) Proton & Neutron Charge Distribution Mississippi State U. D. Dutta Horn et al., Phys.Rev. C78 (2008) 058201 Pion Form Factor R. S. Towell et al., Phys. Rev. D 80, 3715 (1998). up/down sea-antiquark flavor asymmetry FIU, February 2016 5 /33

There is ample evidence that nucleons have some mesonic content in them. Experimental evidence pointed to the nucleon existing ~20% of the time in a virtual meson-nucleon state. J. Arrington, arxiv 1208:4047 (2013) Pasquini and Boffi, Phys. Rev. D 76, 074011 (2007) Kelly, Phys. Rev. C 66, 065203 (2002) Proton & Neutron Charge Distribution Horn et al., Phys.Rev. C78 (2008) 058201 Pion Form Factor R. S. Towell et al., Phys. Rev. D 80, 3715 (1998). up/down sea-antiquark flavor asymmetry Substantial theoretical developments, but Mississippi State U. D. Dutta FIU, February 2016 6 /33

Mississippi State U. D. Dutta FIU, February 2016 7 /33 There is no direct measurement of magnitude of mesonic content of nucleons. In the valance region data comes from pionic Drell-Yan experiments Pion structure function extracted from data disagree with calculations.

Mississippi State U. D. Dutta FIU, February 2016 8 /33 There is no direct measurement of magnitude of mesonic content of nucleons. In the valance region data comes from pionic Drell-Yan experiments Pion structure function extracted from data disagree with calculations. re-analysis Re-analysis after including the gluonic contributions, L. Chang, C. Mexrag, H. Moutarde, C. D. Roberts, J. Rodriguez-Quintero, P. C. Tandy, Phys. Lett. B420, 267 (2014)

Mississippi State U. D. Dutta FIU, February 2016 9 /33 Gluonic contribution also needed to explain the drop in koan/pion ratio at large x. Same Dyson-Schwinger Eq. based calculations with the gluonic contributions can explain the kaon/pion ratio from pionic Drell-Yan experiment. kaon/pion ratio from pionic Drell-Yan experiment at CERN Points to the need for more precise data C. Chen, L. Chang, C. D. Roberts, S. Wan and H.-S. Zong, in preparation (2016).

Outline 1. Introduction - Mesonic content of nucleons 2. Tagged structure functions - Sullivan process and access to meson cloud of nucleon - New experiment at JLab12 3. Tagged DIS at an EIC 3. Summary Mississippi State U. D. Dutta FIU, February 2016 10 /33

Mississippi State U. D. Dutta FIU, February 2016 11 /33 Deep-inelastic Scattering off a virtual-meson cloud is possible experimental technique. The Sullivan process Measuring the contribution to DIS from the Sullivan process is a direct measurement of the mesonic content of the nucleon

Mississippi State U. D. Dutta FIU, February 2016 12 /33 Scattering off a virtual-pion target was used to measure the pion structure function at low-x. In the sea region only data from HERA, no independent confirmation. DIS events with forward going neutrons in coincidence were found to be dominated by pion exchange; extracted pion F2 < 2/3 of proton F2 = xpi Forward neutron data Forward proton data dominated by other resonances and hence could not be used to extract pion structure function

Mississippi State U. D. Dutta FIU, February 2016 13 /33 Spectator Tagging can be used to tag the meson cloud target. Spectator tagging is now an established technique almost free neutron Deuteron Spectator proton (backward going slow proton) Almost-free neutron structure function studied with spectator tagging, technique successfully used by BoNuS PRL 108, 142001 (2012); PRC 89, 045206 (2014)

Mississippi State U. D. Dutta FIU, February 2016 14 /33 Spectator Tagging can be used to tag the meson cloud target. e.g. the Sullivan Process Hydrogen Target detect scattered electron Deuterium Target detect scattered electron neutral meson target (undetected) p p undetected recoiling hadronic system Spectator proton (backward going slow proton) charged meson target (undetected) n p p p Spectator proton undetected recoiling hadronic system detecting two protons with common vertex DIS event reconstruct x, Q 2, W 2, also M X of recoiling hadronic system

Mississippi State U. D. Dutta FIU, February 2016 15 /33 Spectator Tagging will provide the first measurement of tagged structure functions. e.g. the Sullivan Process Hydrogen Target detect scattered electron Deuterium Target detect scattered electron neutral meson target (undetected) p p undetected recoiling hadronic system Spectator proton (backward going slow proton) charged meson target (undetected) n p p p Spectator proton undetected recoiling hadronic system detecting two protons with common vertex DIS event reconstruct x, Q 2, W 2, also M X of recoiling hadronic system

Phenomenological models can be used to interpret the measured tagged structure function. total pion contribution inclusive DIS 100 < Pp < 200 MeV 60 < Pp < 100 MeV 300 < Pp < 400 MeV 200 < Pp < 300 MeV light cone momentum distribution of pions in the nucleon, GπN is the parametrization of Tagged SF pion flux Pion SF the momentum dependence of the πnn vertex function T. J. Hobbs, T. Londergan, W. Melnitchouk, et al. (2014, in preparation); H. Holtmann, A. Szczurek and J. Speth, Nucl. Phys. A 596, 631 (1996); W. Melnitchouk and A. W. Thomas, Z. Phys. A 353, 311 (1995) Mississippi State U. D. Dutta FIU, February 2016 16 /33

Mississippi State U. D. Dutta FIU, February 2016 17 /33 The tagged structure functions can provide the magnitude of the mesonic content of the nucleon. total pion contribution inclusive DIS Pion contribution dominates at JLab kinematic 60 < Pp < 100 MeV 100 < Pp < 200 MeV 200 < Pp < 300 MeV 300 < Pp < 400 MeV Important to note kinematic limits: z < k /M, where k is π 3-momentum = -p 150 < k < 400 MeV/c corresponds to z < ~0.2 Also, x < z! Low x, high W at 11 GeV means Q 2 ~2 GeV 2 T. J. Hobbs, T. Londergan, W. Melnitchouk, et al. (2014, in preparation); H. Holtmann, A. Szczurek and J. Speth, Nucl. Phys. A 596, 631 (1996); W. Melnitchouk and A. W. Thomas, Z. Phys. A 353, 311 (1995)

Mississippi State U. D. Dutta FIU, February 2016 18 /33 For a signal to accidental ratio of 1/10 we can measure the mesonic content by tagging 150-400 MeV/c protons. Pion contribution dominates at JLab kinematic Level of signal for a signal to accidental ratio of 1/10 Important to note kinematic limits: z < k /M, where k is π 3-momentum = -p 150 < k < 400 MeV/c corresponds to z < ~0.2 Also, x < z! Low x, high W at 11 GeV means Q 2 ~2 GeV 2 T. J. Hobbs, T. Londergan, W. Melnitchouk, et al. (2014, in preparation); H. Holtmann, A. Szczurek and J. Speth, Nucl. Phys. A 596, 631 (1996); W. Melnitchouk and A. W. Thomas, Z. Phys. A 353, 311 (1995)

Mississippi State U. D. Dutta FIU, February 2016 19 /33 Pion contributions dominate at JLab kinematics. total pion contribution inclusive DIS 100 < k < 200 MeV T. J. Hobbs, T. Londergan, W. Melnitchouk, et al. (2014, in preparation); H. Holtmann, A. Szczurek and J. Speth, Nucl. Phys. A 596, 631 (1996); W. Melnitchouk and A. W. Thomas, Z. Phys. A 353, 311 (1995) B. Kopeliovich, I. Potashnikova (2015), Rho, Regge

Mississippi State U. D. Dutta FIU, February 2016 20 /33 Tagged structure functions can also be used to extract the pion structure function. inclusive DIS total pion contribution 100 < Pp < 200 MeV 60 < Pp < 100 MeV 200 < Pp < 300 MeV 300 < Pp < 400 MeV Tagged SF (from spectator tagging) pion flux Pion SF

Mississippi State U. D. Dutta FIU, February 2016 21 /33 Tagged structure functions can also be used to extract the pion structure function. Pion flux is largest uncertainty, ~10-20% B. Kopeliovich, I. Potashnikova (2015), Rho, Regge T. Hobbs, W. Melnitchouk, T. Londergan (2014), Rho, Delta But can also be normalize to Drell-Yan data (5% uncertainty).

Mississippi State U. D. Dutta FIU, February 2016 22 /33 Tagged structure functions can also be used to extract the pion structure function. It requires extrapolation to the pion pole low momentum protons helps cover a range of low t Ratio of off-shell to on-shell pion EM form factors 0.6 Q 2 F π (Q 2 ) 0.5 0.4 0.3 0.2 0.1 C.D. Roberts, S. Qin (2015) P 2 = - m 2 π P 2 = + m 2 π P 2 = + 6m 2 π Pion s valence-quark GPDs in unified Dyson-Schwinger Equation framework: virtuality-independent form factor implies virtuality-independent pion structure function This ensures small uncertainty in extrapolation to the pion pole -within ~5% at JLab kinematics 0 0 1 2 3 Q 2 [GeV 2 ]

TDIS is a new experiment to probe the mesonic content of the nucleon. SBS U 40 cm long 10 mm dia. 10 um Al wall 1 atm. @ 77K RTPC V 11 GeV, 50 µa RTPC 5 cm radius of inner electrical wire grid 10 cm radius of middle electrical wire grid 15 cm radius of GEM foil 15.6 cm radius of U&V readout strips Mississippi State U. 40 cm bore, 5T super conduction solenoid D. Dutta 1. Tracker: 5 GEM planes 2. Add calorimeter (LAC from CLAS) 3. RICH or threshold gas Cherenkov 4. PID for trigger level 2: LAC + Cherenkov hadron calorimeter (HCAL) for quasi-elastic neutron calibration Proposal approved for Jlab Hall A: High luminosity, 50 µamp, L = 3 x 1036/cm2 s Large acceptance Super Bigbite ~70 msr, hadron spectrometer HCAL will be used in RTPC calibration Need to Add BONUS-type RTPC, requires solenoidal field Modify SBS for electron detection FIU, February 2016 23 /33

Mississippi State U. D. Dutta FIU, February 2016 24 /33 TDIS is a new experiment to probe the mesonic content of the nucleon. TDIS kinematics - optimized for isolating meson cloud High W 2 - High M x 2 - DIS! Low t, high z x range ~ 0.1 1 < Q 2 < 2 GeV 2 All data obtained simultaneously at one E = 11 GeV setting, only a target change will run hydrogen and deuterium (neutron)

Mississippi State U. D. Dutta FIU, February 2016 25 /33 The conceptual design for a radial TPC has been optimized for the TDIS experiment. RTPC 40 cm long 5 cm radius of inner electrical wire grid 10 cm radius of middle electrical wire grid 15 cm radius of GEM foil 15.6 cm radius of U&V readout strips (1mm x 21.25 mm, with 1mm pitch) Expected resolution ~ 300um, U Readout electronics at the end(s) of the detector V 200 A: Electron Energy deposit 200 B: Proton Energy Deposit 500 450 1 Photo Protons from H p2ds Entries 2329820 Mean x 84.75 Mean y 88.38 500 450 2 Photo Protons from H p2d Entries 2062885 3 Mean x 78.910 Mean y 92.81 Y (mm) 150 100 50 0-50 Y (mm) 150 100 50 0-50 Proton Momentum (MeV/c) 400 350 300 250 200 150 100 RMS x 9.859 RMS y 3 69.9210 2 10 10 Proton Momentum (MeV/c) 400 350 300 250 200 150 100 RMS x 28.63 RMS y 52.91 2 10 10-100 -150-100 -150 50 0 0 20 40 60 80 100 120 140 160 180 Proton Angle (deg.) 1 50 0 0 20 40 60 80 100 120 140 160 180 Proton Angle (deg.) 1-200 -200-150 -100-50 0 50 100 150 200 X (mm) -200-200 -150-100 -50 0 50 100 150 200 X (mm)

Mississippi State U. D. Dutta FIU, February 2016 26 /33 Entries 11938 Mean 1.479 RMS 0.4174 The conceptual design for a radial TPC has been optimized for the TDIS experiment. 480 Cylindrical Triple GEM 0 Window 20 µ m Be 150 Field Wire 12.7 µ m W Window 20 µ m Be 400 15 deg. 50 Target 10 mm diam, 10 µ m Al wall 2 atm H/D @ 25 deg. K RTPC Gas: 0.05 atm He @ 25 deg. K W Colli 7 mm bore 35 mm length 375 W Colli 5 mm bore 70 mm length 200 Outer pressure/temperature containment vessel The protons of interest have large transverse momentum and can be separated from background electrons using the solenoidal magnet. The proton of interest can be separated from accidentals using vertex reconstruction. Integrated Energy Deposit (MeV) 7 10 6 10 5 10 4 10 3 10 2 10-1 10-2 10 10 10 1-3 B: Target Dependence 3S Solenoid Field D 2 : 2 atm, 25 K H 2 : 2 atm, 25 K H 2 : 2 atm, 77 K rr0 Entries 16891 Mean 1.479 RMS 0.4187 confinement of Møller electrons rr0 Will require a level-3 trigger or a streaming DAQ -4 10 0 20 40 60 80 100 120 140 Radial Dist from Beam Axis (mm)

Mississippi State U. D. Dutta FIU, February 2016 27 /33 The TDIS experiment will measure tagged structure functions for protons and neutrons proton target total pion contribution inclusive DIS Colored lines are pion contribution for different bins in p proton Data for 200 < p proton <250 MeV/c are representative to show uncertainty Full momentum range (collected simultaneously) - all momentum bins in MeV/c Error bars largest at highest x points - at fixed x, these are the lowest t values

Mississippi State U. D. Dutta FIU, February 2016 28 /33 The TDIS experiment will measure tagged structure functions for protons and neutrons neutron target total pion contribution inclusive DIS Colored lines are expected total Delta and rho contribution for 250 < p proton < 400 MeV/c. Data for pion contribution are representative to show uncertainty Full momentum range (collected simultaneously) - all momentum bins in MeV/c run at lower luminosity due to larger background

Mississippi State U. D. Dutta FIU, February 2016 29 /33 The TDIS experiment will also extract the pion structure function. - Large x structure of the pion is of particular recent interest, verify resummed Drell-Yan results - Q 2 range will check evolution - Large x, low Q complementary to HERA low x, high Q - Low t extrapolation to the pion pole Will also measure n, p (π, π 0 ) difference - look for isospin dependence

Outline 1. Introduction - Mesonic content of nucleons 2. Tagged structure functions - Sullivan process and access to meson cloud of nucleon - New experiment at JLab12 3. Tagged DIS at an EIC 3. Summary Mississippi State U. D. Dutta FIU, February 2016 30 /33

Mississippi State U. D. Dutta FIU, February 2016 31 /33 TDIS experiments at an EIC would cover a large kinematic range. Simulated uncertainty for: 5 GeV e - on 25 GeV p spectator neutron tagging & luminosity = 10 32 cm -2 s -1 (for 10 6 s) Forward neutron angle < 50 mrad Q 2 > 1 GeV 2 1.15 1.1 1.05 1 0.95 0.9 0.85 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 x π R. J. Holt & P. Reimer, AIP Conf. Proc. 588, 234 (2001)

Mississippi State U. D. Dutta FIU, February 2016 32 /33 TDIS experiments at an EIC would cover a large kinematic range. Simulated uncertainty for: 5 GeV e - on 25 GeV p spectator neutron tagging & luminosity = 10 32 cm -2 s -1 (for 10 6 s) Forward neutron angle < 50 mrad Q 2 > 1 GeV 2 1.15 1.1 1.05 1 0.95 with forward protons detection kaon structure can be studied with 2 H, 4 He beams, pion structure in nuclear medium can be studied. 0.9 0.85 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 x π K. Park working on simulation suite for tagged measurements at EIC R. J. Holt & P. Reimer, AIP Conf. Proc. 588, 234 (2001)

Mississippi State U. D. Dutta FIU, February 2016 33 /33 Summary 1. Tagged DIS: Spectator tagging, provide new tools to study the structure of nucleons. 2. Spectator tagging can provide access to the mesonic content of the nucleon structure and the pion structure function. 3. A new experiments at JLab have been proposed to take advantage of these new avenues during the 12 GeV era. 4. These studies can be extended to a wide range of complimentary kinematics at an EIC. This work is supported by US Dept. Of Energy under contract # DE-FG02-07ER41528