Yi Qiang Duke University for CIPANP 2009 May 27, 2009 The first measurement of neutron Transversity using a transversely polarized 3He target Good morning… My name is Yi Qiang, from Duke University I will talk about the first measurement of neutron transversity using a transversely polarized 3He target Yi Qiang Duke University for CIPANP 2009 May 27, 2009 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Outline Overview of leading twist TMDs Jefferson Lab Experiment E06-010 First neutron Transversity experiment Experimental configuration Polarized 3He target Detector performance Current Status and Future Plan In this talk, I will first introduce the background about the nucleon transverse momentum distributions. Then I will talk about the details of this neutron transversity experiment performed in Jefferson Lab Hall A including … At the end, I will summarize with the current status and the future plan. 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Nucleon Structure from DIS Un-polarized Nucleon Structure Function Longitudinal Momentum Distribution Well probed for 50 years over very large kinematics range Longitudinal Polarized Nucleon Structure Functions Since “spin crisis” in 1980s Plotted in fairly large range Transversity: Can be probed in Semi-Inclusive DIS New business: recent measurements from HERMES and COMPASS using Hydrogen and Deuteron targets f1 = g1 = Deep inelastic lepton-hadron scattering (DIS) has played a seminal role in the development of our present understanding of the sub-structure of hadrons. Since the discovery of the parton from the Bjorken scaling in the late 1960s, the unpolarized structure function f1 has been measured with excellent precision over a large range of the kinematics including the longitudinal momentum fraction x and momentum transfer Q2. Motivated by the original “spin crisis” from the EMC experiment in the 1980s, the nucleon longitudinal spin structure g1 has been determined through polarized DIS with good precision. If we look at a nucleon from a more realistic 3D point of view, other than the unpolarized and longitudinal nucleon structure functions, the least known part is the transverse spin and momentum distributions. Transversity describes the quark transverse polarization in a transversely polarized nucleon, and its difference to the longitudinal parton distribution reveals the relativistic nature of the quarks inside the nucleon. Because Transversity is chiraly-odd, it can not be measured through inclusive DIS, but one can probe it through single target spin azimuthal asymmetries from semi-inclusive DIS processes with a transversely polarized target. In this process, it’s convoluted to the Collins fragmentation function which describes the correlation between the fragmenting quark’s transverse spin and the outgoing hadrons' transverse momentum. The COMPASS and HERMES collaborations have recently reported first SIDIS asymmetries on transversely polarized proton and deuteron targets and the business has just started! h1 = 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Leading Twist TMDs Blue: kT independent; Red: T-odd Quark polarization Un-Polarized Longitudinally Polarized Transversely Polarized Nucleon Polarization U L T f1 = h1 = g1 = h1L = Including the previously mentioned three distributions, totally eight transverse momentum dependent distribution functions, TMDs, are identified in the leading twist. They are listed in this table. h1 = f 1T = g1T = h1T = 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Access Leading Twist Parton Distributions through Semi-Inclusive DIS SL, ST: Target Polarization; le: Beam Polarization Unpolarized Polarized Target Beam and Boer-Mulder Transversity Sivers Pretzelosity All the eight leading twist TMDs can be measured through semi-inclusive DIS by using different combinations of beam and target polarizations. In this experiment, we used a transversely polarized 3He target, therefore, by only considering the target single spin asymmetry, we can measure Transversity, Sivers and Pretzelosity distribution functions. The physical meanings of Transversity has been mentioned. The Sivers function refers to the correlation between the nucleon’s transverse spin and the quark’s transverse momentum, which involves the quark orbital motion The Pretzelosity describes the difference between the helicity and transversity distribution and measures the relativistic effects in the nucleon. Since the electron beam was polarized as well during the experiment, we parasitically measured the double spin azimuthal asymmetry for the g1T distribution function. g1T describes the quark longitudinal polarization in a transversely polarized nucleon and is non-vanishing only if the quark orbital angular momentum is non-zero. 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Transversity from JLab Hall A Linear accelerator provides continuous polarized electron beam Ebeam = 6 GeV Pbeam = 85% 3 experimental halls This is where the experiment performed: Jefferson Lab, located in Newport News Virginia. The Jefferson Lab accelerator has two LINACs forming a circle and it can delivery electron beam up to 6 GeV with polarization around 85%. There are three experimental Halls at the end of the beam line and they are Hall A, B and C. The neutron transversity I’m reporting was carried out in Hall A. A C B 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

E06-010 Collaboration E06-010: Single Target-Spin Asymmetry in Semi-Inclusive n↑(e, e’p±) Reaction on a Transversely Polarized 3He Target Spokespersons: Xiaodong Jiang (Rutgers/Los Alamos, Contact Person), Jian-ping Chen (JLab), Evaristo Cisbani (INFN-Rome), Haiyan Gao (Duke), Jen-Chieh Peng (UIUC) Thesis Students: C. Dutta (Kentucky), J. Huang (MIT), A. Kalyan (Kentucky), J. Katich (W&M), X. Qian (Duke), Y. Wang (UIUC), Y. Zhang (Lanzhou U) Approved with A rating and was just finished in early February, 2009. This experiment is supported by a world-wide collaboration and we have 7 PhD thesis student in total. In early February this year, we just finished the three months’ data taking. 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

E06-010 Setup g* p e’ e Electron beam: E = 5.9 GeV 40 cm polarized 3He target BigBite at 30 degrees as electron arm: P = 0.7 ~ 1.8 GeV/c HRSL at 16 degrees as hadron arm: P0 = 2.35 GeV/c Measure Collins, Sivers and pretzelosity asymmetries in valence range: x = 0.1 ~ 0.4 p HRSL 16o e g* e’ BigBite 30o The experimental is configured as following. We have 5.9 GeV polarized electron beam incident on a 40 cm polarized 3He target. The scattered electron was detected by the BigBite spectrometer positioned 30 degrees to the beam right. And the momentum range is … The produced hardon was detected coincidently using the left high resolution spectrometer 16 degrees to the beam left. And the momentum setting is 2.35 GeV/c. This setup allowed us to measure the … asymmetries in the valence range … Polarized 3He Target 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Separation of Collins, Sivers and Pretzelosity effects through angular dependence Rotate target spin direction to increase fs coverage Vertical Horizontal Transversity The separation of the three single spin azimuthal asymmetries will be done based on their different angular dependences. Let me first define two important azimuthal angles around the 4 momentum transfer: fs is the target spin direction and fh is the hadron direction and both angles are defined with respect to the electron scattering plane. The transversity distribution is modulated by the sum of fs and fh, sivers distributions by the difference of fs and fh and the pretzelosity has the dependence on 3fh – fs. Due to the small acceptance of the left HRS, in order to increase the angular coverage, we polarized the 3He spin in four directions around the beam and they are marked by the arrows: vertical up and down, horizontal left and right. Sivers Pretzelosity 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Polarized 3He Target Effective polarized neutron target ~90% ~8% ~1.5% Effective polarized neutron target High luminosity: L(n) = 1036 cm-2 s-1 Fast spin exchange with K/Rb hybrid cells Oven 230 oC Laser 795 nm F = 3” Pumping Chamber The 3He target is widely used as an effective polarized neutron target. Because the two protons in the 3He nucleus will most likely form a pair, about 90% of the 3He spin is carried by the single neutron. The 3He target we used is high pressure cell and was polarized through spin-exchange optical pumping. It has 10 atm 3He inside which allows the luminosity to be as high as 10 to the 36 level with 10 uA beam. We also put K and Rb alkali metal into the cell as the spin transfer medium. Here is the picture of a 3He cell. It has two parts. The lower part is the 40 cm long target chamber and the electron passes through it. Top part is the 3 inch spherical pumping chamber where the optical pumping happens. We put the pumping chamber into a oven and heat it up to 230 degrees so that we have some amount of alkali vapor in it. The whole target was put in a uniform 25 G magnetic field, and a circular polarized high power laser was shot to the pumping chamber. The wave length of the laser is chosen to be the D1 transition of the Rb atom, so with the existance of the external magnetic field, the Rb atom will be polarized by the laser. Then the spin of the Rb atoms will be first transferred to K and then to the 3He nuclei. Actually, the spin of the Rb atom can be directly tranfered to 3He, but with K as a middle stage, the spin exchange efficiency got greatly improved! 25 G Holding Field 40 cm Target Chamber 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Target Setup for Transversity New vertical coil together with existing horizontal coils and new oven allow 3He to be polarized in ALL three directions! New narrow band COMET lasers make optical pumping more efficient. 3He spin pumped to horizontal and vertical directions. Auto spin flip every 20 minutes. For the Transversity experiment, the Hall A 3He target got upgraded mainly in the following ways vertical coil and oven comet lasers spin direction auto flip by 180 degree every 20 minutes though adiabatic fast passage to reduce the systematic error. 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

3He Target Polarimetries Water NMR NMR: Nuclear Magnetic Resonance Free NMR at pumping chamber from every auto spin flip. Target chamber polarization is calibrated by Water NMR measurement. EPR: Electron Paramagnetic Resonance Got signal from both K and Rb. Measures pumping chamber polarization. EPR We used two polarimetries to cross calibrate the target polarization 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Target Performance Online Preliminary Online preliminary EPR/NMR analysis shows a stable 65% polarization with 15 mA beam and 20 minute spin flip Cell: Astral Cell: Maureen The target performance is very good throughout the experiment. The … The plot shows the polarization history from the beginning of the experiment till the Christmas shut down. Since the first high pressure 3He cell was used in the SLAC E142 experiment in early 1990s, the effort to improve the target polarization has never been stopped. With some many technique breakthrough such as hybrid cell and narrow band laser, we just set the bar to a new height for the future 3He experiment. Online Preliminary 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

BigBite Spectrometer 30 degrees to the beam right Detect electrons A big bite of acceptance DW = 64 msr P : 700 ~ 1800 MeV/c 3 Wire Chambers: 18 planes Optics is crucial for the angular dependence separation and kinematics variables Pre-Shower and Shower for electron PID 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

BigBite Optics Optics for both negative and positive charged particles have been done Wire Chamber Spatial Resolution: 180 mm Vertex Resolution: 1 cm Angular Resolution: < 10 mrad Momentum Resolution: 1% BigBite Sieve Slit Because of the large acceptance of the BigBite, even with a dipole magnet, both negative and positive charged particles can be detected at the same time. Therefore, the optics for both neg and pos … Spatial resolution achieved the design goal Vertex resolution: 1cm will allow us to do vertex coincident cut Angular resolution: put sieve plate which is made of 1.5’’ lead in front of the BigBite magnet Momentum resoluton 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Electron Selection in BigBite Pre-shower/Shower have been calibrated Energy Resolution: 8% Well separated electrons and pions 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Left High Resolution Spectrometer ep Coincidence Time s < 400 ps p K 16 degrees to beam left with p0 = 2.35 GeV/c Clean e/p separation with Gas Cherenkov and Pion Rejector Vertex and TOF coincidence with BigBite will help reduce the background Kaon asymmetry data can also be extracted: A1: Pion rejection > 90 % RICH: K/p separation ~ 4 s TOF: K/p separation ~ 4 s Cherenkov Ring from RICH 4 s Separation 1. 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Kinematics Coverage x<0.25 x>0.25 y Q2 W’ z x Pretzelosity Angle: 3fh-fs Sivers Angle: fh-fs Collins Angle: fh+fs y 0.6 ~ 0.9 x<0.25 0.6 ~ 3 (GeV/c)2 Q2 W’ Y: forwardness Q2: momentum transfer W’: missing mass, above main resonance region Z: fraction of the energy transfer, selecting leading hadron in the fragmentation Pt: transverse momentum up to ~ 0.5 GeV Have pretty much 1.5 ~ 2.3 (GeV/c2) x>0.25 0.4 ~ 0.6 z 0.25 0.5 x 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Projections of Collins and Sivers Functions This is the projection of our data with pure statistic uncertainties. If we divide x into 4 bins, both Collins and Sivers asymmetry have the statistic uncertainty from 3 to 5 percent. 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Projections of g1T First Neutron (3He) Measurement With Fast Beam Helicity Flip (30Hz) Projected Uncertainties (Stat. Only): 2.3% at low x 3.4% at high x The statics uncertainty of g1T is very similar to Sivers uncertainty except for the addition beam polarization term and this will make the error bars slightly larger. The plotted g1T was estimated from g1 through Lorentz Invariance Relations and Wandzuraand Wilczek Relations. 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

The 12 GeV upgrade of Jefferson Lab will bring more lights on the future neutron transversity experiment. We are proposing a new measurement with the new Solenoid spectrometer on a transversely polarized target. Benefited of the large acceptance of the new solenoid spectrometer and higher beam energy, we can plot out the neutron transversity in a much larger kinematic range with much higher precision. 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Status of E06-010 The experiment was smoothly performed from Oct 2008 to Feb 2009. Statistics exceeded the approved goal. Detector calibrations and target analysis are ongoing. Will start to extract physical asymmetries afterwards. 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Summary First measurement of neutron transversity from polarized 3He Target. Data will cover valence quark range: x = 0.1~0.4 High luminosity and statistics: Absolute error on neutron pion asymmetries is about 3%~5%. Preliminary results coming out really soon! 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Backup Slides 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Collaboration members E06-010 Collaboration Institutions California State Univ., Duke Univ., Florida International. Univ., Univ. Illinois, JLab, Univ. Kentucky, LANL, Univ. Maryland, Univ. Massachusetts, MIT, Old Dominion Univ., Rutgers Univ., Temple Univ., Penn State Univ., Univ. Virginia, College of William & Mary, Univ. Sciences & Tech, China Inst. Of Atomic Energy, Beijing Univ., Seoul National Univ., Univ. Glasgow, INFN Roma and Univ. Bari, Univ. of Ljubljana, St. Mary’s Univ., Tel Aviv Univ. Collaboration members A.Afanasev, K. Allada, J. Annand, T. Averett, F. Benmokhtar, W. Bertozzi, F. Butaru, G. Cates, C. Chang, J.-P. Chen (Co-SP), W. Chen, S. Choi, C. Chudakov, E. Cisbani(Co-SP), E. Cusanno, R. De Leo, A. Deur, C. Dutta, D. Dutta, R. Feuerbach, S. Frullani, L. Gamberg, H. Gao(Co-SP), F. Garibaldi, S. Gilad, R. Gilman, C. Glashausser, J. Gomez, M. Grosse-Perdekamp, D. Higinbotham, T. Holmstrom, D. Howell, J. Huang, M. Iodice, D. Ireland, J. Jansen, C. de Jager, X. Jiang (Co-SP), Y. Jiang, M. Jones, R. Kaiser, A. Kalyan, A. Kelleher, J. Kellie, J. Kelly, A. Kolarkar, W. Korsch, K. Kramer, E. Kuchina, G. Kumbartzki, L. Lagamba, J. LeRose, R. Lindgren, K. Livingston, N. Liyanage, H. Lu, B. Ma, M. Magliozzi, N. Makins, P. Markowitz, Y. Mao, S. Marrone, W. Melnitchouk, Z.-E. Meziani, R. Michaels, P. Monaghan, S. Nanda, E. Nappi, A. Nathan, V. Nelyubin, B. Norum, K. Paschke, J. C. Peng(Co-SP), E. Piasetzky, M. Potokar, D. Protopopescu, X. Qian, Y. Qiang, B. Reitz, R. Ransome, G. Rosner, A. Saha, A. Sarty, B. Sawatzky, E. Schulte, S. Sirca, K. Slifer, P. Solvignon, V. Sulkosky, P. Ulmer, G. Urciuoli, K. Wang, Y. Wang, D. Watts, L. Weinstein, B. Wojtsekhowski, H. Yao, H. Ye, Q. Ye, Y. Ye, J. Yuan, X. Zhan, Y. Zhang, X. Zheng, S. Zhou. 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

Fermi Lab E704: p↑p→pX at 400 GeV 5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009

5/27/2009 Neutron Transversity in JLab Hall A CIPANP 2009