Tensor Polarized Deuteron at and EIC

Transcription

1 Tensor Polarized Deuteron at and EIC Tensor Polarized Observables Workshop March 10-12, 2014 Narbe Kalantarians Hampton University

2 Outline Background/Motivation Spin-1/Tensor-Polarization Concept Starting point (Spin-1) Physics with an EIC p n 2

3 Why Deuteron? Spin-1 system Simple lab for nuclear physics Reasonably easy to polarize. p n Spatial distribution depends on the spin state J. Carlson, R. Schiavalla Rev. Mod. Phys (1998) J.L. Forrest et al. Phys. Rev. C (1996) M = 0 M = ±1 3

4 Spin-1 Spin-1 system in a B-field leads to 3 sublevels via Zeeman interaction. m = n- n 0 n+ z Vector polarization: (n+ - n - ); -1 < P z < +1 Tensor polarization: (n+ - n 0 ) (n 0 - n-); -2 < P zz < +1 Normalization: (n + + n - +n 0 ) = 1 Some research has been done with deuteron beams (Thesis: V. Morozov) 4

5 Tens. Pol. Scattering at low x Possibilities Small x aspect of tensor pol. (deuteron) could access anti-shadowing and 2 nucleon (coherent) scattering. A good starting point would be to extract b 1 d with an EIC. Issues to Address: How well can polarization, beam stability be understood and controlled? Need simulation studies.. 5

6 Inclusive Scattering with Spin-1 l ' l θ l q Frankfurt & Strikman (1983) Hoodbhoy, Jaffe, Manohar (1989) D M W d 2 σ! 1 =σ dωde ' Mott y F 2(x,Q 2 )+ 2 M F $ # 1(x,Q 2 )tan 2 (θ / 2) &+γg 1 (x,q 2 )+δg 2 (x,q 2 ) " % +ςb 1 (x,q 2 )+εb 2 (x,q 2 )+ζb 3 (x,q 2 )+ηb 4 (x,q 2 ) b 1,b 2 ~ 1 P zz eff Spin-1 => 4 more structure-functions: b 1,b 2,b 3,b 4 6

7 b 1 d b d 1 1 ( 2 q0 q 1 ) Deuteron essentially combination of nuclear and quark physics. Measured via DIS, but dependent on deuteron spin-state. Allows for investigation of nuclear effects at parton level.. 7

8 b 1 d Hoodbhoy,Jaffe, Manohar (1989) b 1 vanishes in the absence of nuclear effects. i.e., if Details in S. Kumano, G. Miller, S. Liuti Talks d = p + n p,n in relative S-state Even accounting for D-state admixture, b 1 d expected to be very small. Khan & Hoodbhoy, PRC 44,1219 (1991) : b 1 O(10-4 ) Relativistic convolution model with binding Umnikov, PLB 391, 177 (1997) : b 1 O(10-3 ) Relativistic convolution with Bethe-Salpeter formalism 8

9 Experimental Method Observable is the Normalized XS Difference " σ meas = σ U 1 P B P Z A P % ZZ A ZZ # $ & ' PRL (2005) A zz = 1 P zz 2σ 1 2σ 0 3σ U b 1 =- 3 2 F 1A zz ( P ZZ = n+ + n ) 2n 0, 2 < P n + + n + n 0 ZZ <1 9

10 HERMES Measurement:b 1 d PRL (2005) b 1 =- 3 2 F 1 A zz A zz = 1 P zz 2σ 1 2σ 0 3σ U Rising of b 1 as x->0 can be related to same mechanism responsible for nuclear shadowing. Ashman,et al. PLB (1988) Can also be described in models involving double-scattering of leptons HERMES Details in C. Riedl s talk. Proposed measurement at JLab (K.Slifer s talk). 10

11 b 1 d Predictions Z.Phys. A (1997), Phys.Rev. C (1998) Bonn OBE Paris Both models predict b 1 (rapidly) increasing as x->0: Double-scattering Errors for (HERMES) data shown are statistical only.. 11

12 Predictions for b 2d, A zz d Phys.Rev. D (1998) Phys.Lett. B (1997) Disentangling possible at lower x. (HERMES) errors are statistical here.. 12

13 Tens. Pol. Scattering at low x L. Frankfurt, V. Guzey, M. Strikman Mod. Phys.Lett. A21(2006) Solid curve: Q 2 2 GeV 2 Dashed: 5 GeV 2 Dotted: 10 GeV 2 " T 20 = 2 σ + σ 0 $ # σ + +σ 0 % ' & b d 1 (x,q 2 ) = F d 2 (x,q 2 ) T 20 (x,q 2 ) 2x 13

14 The (M)EIC at JLab 12 GeV CEBAF is a fullenergy lepton injector e injection Parallel running with fixed target possible Hall D Both the MEIC and CEBAF have a 1.4 km circumference IP1 IP2 High-Energy Arc (Stage II) Prebooster CEBAF Ion linac Halls A-C MEIC can store GeV protons, or heavy ions up to 40 GeV/A. The stage II EIC will increase the energy to 250 GeV for protons and 20 GeV for electrons. Two detectors IP2 could host ephenix 14

15 MEIC design goals P. Nadel-Turonski EICAC 2014 EIC MEIC MEIC Spin control for all light ions Figure-8 layout Vector- and tensor polarized deuterium Full-acceptance detector Ring designed around detector requirements Detection of all fragments nuclear and partonic (arxiv: ) Stable concept detailed design report released August

16 EIC Staging Already the first stage of an EIC gives access to sea quarks and gluons Need polarization and good acceptance to detect spectators & fragments An EIC aims to study the sea quark and gluon-dominated matter. Stage I JLab 12 GeV Stage I+II 16

17 MEIC full-acceptance detector Design goals: 1. Detection/identification of complete final state 2. Spectator p T resolution << Fermi momentum 3. Low-Q 2 electron tagger for photoproduction low-q 2 electron detection (from GEANT4, top view) e large-aperture electron quads ion quads IP ~60 mrad bend far forward hadron detection FP n, γ p EM calorimeter 50 mrad beam (crab) crossing angle dual-solenoid in common cryostat 4 m inner coil e/π threshold Cherenkov barrel DIRC + TOF Tracking EM calorimeter central detector with endcaps RICH + TORCH? EM calorimeter small-diameter electron quads Endca p 1 m 2 Tm dipole Thin exit windows 1 m Ion quadrupoles Electron quadrupoles Fixed trackers Trackers and donut calorimeter Roman pots 17

18 Polarized Deuterons in Figure-8 Longitudinal Transverse (arxiv: ) Maintaining pol. deuteron difficult with present tech., due to small magnetic moment. Figure-8 design allows one to control the stable spin orientation with a small spin rotation around a certain axis using magnetic inserts. Deuteron pol. is then stable and points along the rotation axis at the insert s location. Simulation in progress for MEIC (figure-8) concept.. 18

19 Deuteron Beam Polarization Studies Studied deuteron spin manipulation with a 270 MeV vertically polarized beam stored in IUCF storage ring. Similar study done at COSY. Beam Fast RF cycled through 4 vertical polarization states (to reduce systematic errors). Spin-1 linear combination: Flip by bunches or extract at experiment. (P V,P T ) = (1,1),( 1,1),(0,1),(0, 2) Thesis: V. Morozov) 19

20 Summary Tensor Polarized deuteron provides Spin-1 quark/nuclear system. Spin-1 produces 4 new SSFs. HERMES measurement, complementary proposal at Jlab. Access to lower x, with tensor polarized deuteron, could open new physics capabilities. b 1 d would be a good starting point. Study underway for polarized deuteron beam for MEIC. *Many thanks to C. Weiss, V. Morozov, S. Liuti, P. Nadel-Turonski 20

21 Support Slides 21

22 Spin-1 Structure Functions Leading Twist: F 1,g 1,b 1 1 F 1 2 g q Nucleon e q 2 e q 2 b 1... q $ % q 1/2 +q 1/2 $ % q 1/2 q 1/2 & ' & ' Deuteron F 1 : quark distributions averaged over spin states g 1 : difference of distributions of quarks aligned/anti-aligned with nucleon b 1 : difference of helicity-0/helicity non-zero states of the deuteron 1 2 q e 2 q " # q 0 q 1 $ % q 0 = (q 0 +q 0 ) = 2q 0 q 1 = (q 1 +q 1 ) = (q 1 +q 1 ) 22

23 Spin-1 Structure Functions Nucleon b 1... From reflection-symmetry q m = q m 1 2 q Deuteron e 2 q $ % 2q 0 (q 1 +q 1 )& ' b 1 d.n.e for spin-1/2 and vanishes in absence of nuclear effects. In relative S-state b 1 describes difference between helicity-0 and averaged nonzero. q 0 = (q 0 +q 0 ) = 2q 0 q 1 = (q 1 +q 1 ) = (q 1 +q 1 ) b 1 depends on spin-averaged distributions 1 2 q e 2 q " # q 0 q 1 $ % Hoodbhoy,Jaffe, Manohar (1989) 23

24 Spin-1 Structure Functions Leading Twist: F 1,g 1,b 1 F 1 g 1 b q q Nucleon e q 2 e q 2 $ % q 1/2 +q 1/2 $ % q 1/2 q... 1/2 & ' & ' 1 2 q Deuteron e 2 q " # q 0 q 1 $ % b 2 : related to b 1 by relation similar to Callan-Gross. b 4 : kinematically suppressed at longitudinal polarization. Also, leading twist. b 3 : higher twist, similar to g 2. 24

25 HERMES Measurement:A zz d **HERMES result was about 2σ from 0. PRL (2005) 27.6 GeV longitudinally polarized positron beam Internal tensor polarized d 2 gas target; P zz ~0.8 (negligible P z ), dilution~ month of data taking. Tensor spin asymmetry A zz = 1 P zz 2σ 1 2σ 0 3σ U 0.01< x < < Q 2 < 5GeV 2 25

26 HERMES Measurement:b 2 d Thesis: C. Riedl b 2 related to b 1 via Callan-Gross-type relation.! 1+R $ b 2 = 2xb 1 # & " 1+γ 2 % R = (1+γ 2 ) F 2 2xF

27 HERMES Close-Kumano Sum Rule F.E.Close,S.Kumano, PRD (1990) If sea quark and antiquark tensor polarization vanishes i.e. b 1 (x)dx = 0 HERMES measurement: b 1 (x)dx = ± ± b 1 (x)dx = ± ± σ result, over measured range 1.7σ result, with Q 2 >1GeV 2 PRL (2005) 27

28 Proposal To Determine b 1 d at JLab Measurement at Jlab 12GeV could be complementary to HERMES. Advantage would be higher luminosity: ~10 35 cm -2 s -1 compared to ~10 31 cm -2 s -1. Some research has been done tensor polarizing solid deuteron (ND 3 ) target via NMR*: P zz ~0.2, dilution~0.24,0.36. Submitted at PAC 40; Conditionally approved. 28

29 MEIC accelerator parameters 50 5 GeV GeV 2 Proton Electron Proton Electron Beam energy GeV Collision frequency MHz Particles per bunch Beam Current A Polarization % ~80 >70 ~80 >70 Energy spread 10-4 ~3 7.1 ~3 7.1 RMS bunch length mm Horizontal emittance, normalized µm rad Vertical emittance, normalized µm rad Horizontal and vertical β* cm 10 and 2 10 and 2 10 and 2 10 and 2 Vertical beam-beam tune shift Laslett tune shift < <0.001 Distance from IP to 1 st quad m 7 (downstream) 3.5 (upstream) 3 7 (downstream) 3.5 (upstream) Luminosity * Includes space-charge per IP* effects and cm -2 sassumes -1 conventional 2.4 x electron cooling 8.3 x Red indicates parameters specific to the full-acceptance detector 29 3