Weak form factors and standard model tests. Gordon D. Cates University of Virginia

Transcription

1 Weak form factor and tandard model tet Gordon D. Cate Univerity of Virginia QCD and Hadron Phyic Town Meeting - Rutger- January 12, 2007

2 The Z 0 ha hown itelf to be an increaingly veratile probe over the pat 2+ decade e - Z 0 p Etablihing the tandard model. Exploring the role of trange quark in hadronic tructure. Searching for phyic beyond the tandard model. e - p Weak amplitude can be readily tudied by meauring parity violating aymmetrie that reult from their interference with electromagnetic amplitude.

3 The Z 0 ha hown itelf to be an increaingly veratile probe over the pat 2+ decade e - Z 0 p Etablihing the tandard model. Exploring the role of trange quark in hadronic tructure. Searching for phyic beyond the tandard model. e - p Exciting and divere new application are coming. For example: PREx: Mapping out the neutron ditribution in lead. Studying charge ymmetry violation (CSV) in the parton ditribution function. Weak amplitude can be readily tudied by meauring parity violating aymmetrie that reult from their interference with electromagnetic amplitude.

4 Parity violating pin-aymmetry in elatic cattering from the proton The parity violating pin-aymmetry that reult from elatic cattering off the proton i rich with divere type of phyic!

5 Parity violating pin-aymmetry in elatic cattering from the proton The parity violating pin-aymmetry that reult from elatic cattering off the proton i rich with divere type of phyic! Thi term i proportional to the weak charge.

6 Parity violating pin-aymmetry in elatic cattering from the proton The parity violating pin-aymmetry that reult from elatic cattering off the proton i rich with divere type of phyic! Thi term i proportional to the weak charge. Thi term i proportional to hadronic tructure, including the trange-quark form factor.

7 Parity violating pin-aymmetry in elatic cattering from the proton The parity violating pin-aymmetry that reult from elatic cattering off the proton i rich with divere type of phyic! Thi term i proportional to the weak charge. Thi term i proportional to hadronic tructure, including the trange-quark form factor. Thi term i proportional to the neutral weak axial form factor, and contain contribution from thing uch a the anapole moment.

8 In PV elatic e-p cattering, different kinematic emphaize different phyic Weak charge Hadronic Weak charge Hadronic 0.85 ppm ppm 0.64 ppm ppm 0.43 ppm 7.50 ppm 0.21 ppm 3.75 ppm 0 ppm Qweak Q 2 = 0.03 GeV 2 Happex II p Q2 = 0.1 GeV2 Happex I Q 2 = GeV 2 0 ppm The relative contribution from the weak charge and hadronic tructure change dramatically depending on the Q 2

9 experiment to meaure trange form factor HAPPEX forward angle, integrating, GE GM at Q2=0.48 GeV2 GE GM at Q2=0.1 GeV2 GE at Q2=0.1 GeV2 (4He) SAMPLE Open geometry, backward angle, integrating, GM and GA at Q2=0.1 GeV2 A4 (Mainz) fat-counting calorimeter for background rejection GE GM at Q2=0.23 GeV2 GE GM at Q2=0.1 GeV2 GM, GA at Q2=0.1, 0.23, 0.5 GeV2 G0 fat counting, open geometry with ToF for background rejection GE + η GM over Q2=[0.12,1.0] GeV2 GM, GA at Q2= 0.23, 0.63 GeV2

10 Experimental approach for Happex Polarized electron are cattered off proton or 4 He nuclei in a 20 cm 400W tranvere-flow LH 2 or highpreure 4 He target.

11 Experimental approach for Happex Polarized electron are cattered off proton or 4 He nuclei in a 20 cm 400W tranvere-flow LH 2 or highpreure 4 He target. Elatically cattered electron are detected uing a high-reolution pectrometer (eptum + QQDQ) at 4-8 and 5 mtr/pectrometer arm.

12 Experimental approach for Happex Polarized electron are cattered off proton or 4He nuclei in a 20 cm 400W tranvere-flow LH2 or highpreure 4He target. Elatically cattered electron are detected uing a high-reolution pectrometer (eptum + QQDQ) at 4-8 and 5 mtr/pectrometer arm. High rate (120 MHz for H and 12 MHz for 4He) are handled uing integrating Cherenkov detector.

13 Data from Happex II proton run (A raw correction 11 ppb) Hitogram of aymmetrie aociated with individual pule pair how Gauian behavior over ix decade Aymmetrie aociated with each lug - a group of run taken for a given halfwave plate etting. Q 2 = / GeV 2 A raw = / ppm (tat)

14 Overall, there ha been tremendou progre on our undertanding of G E and G M. At Q 2 = 0.1 GeV 2 : A4 SAMPLE with G A calculation 0.05 GE Q ~ 0.1 GeV G M Pre-Happex II pre-g0 time period with only A4 (Mainz) and SAMPLE

15 Overall, there ha been tremendou progre on our undertanding of G E and G M. At Q 2 = 0.1 GeV 2 : 0.15 A4 SAMPLE with G A calculation 0.15 A4 G0 (extrapolated) SAMPLE with G A calculation HAPPEX-H (2005) GE GE HAPPEX- He (2005) Q ~ 0.1 GeV Q ~ 0.1 GeV G M Pre-Happex II pre-g0 time period with only A4 (Mainz) and SAMPLE G M All reult, including SAMPLE, A4, Happex II, and G0 extrapolated to 0.1 GeV 2

16 Overall, there ha been tremendou progre on our undertanding of G E and G M. At Q 2 = 0.1 GeV 2 : A4 SAMPLE with G A calculation G0 (extrapolated) 0.05 HAPPEX-H (2005) 0.05 HAPPEX-H (2005) GE HAPPEX- He (2005) GE HAPPEX- He (2005) Q ~ 0.1 GeV Q ~ 0.1 GeV G M Happex II only G M All reult, including SAMPLE, A4, Happex II, and G0 extrapolated to 0.1 GeV 2

17 Current and future data on G E + ηg M at forward angle at all Q 2 M + G 0.2 Black line how very imple naive fit. G E 0.1 Data are uggetive of poitive value, but would be unlikely to convince a keptic. 0.0 G0 (FORWARD) MAMI A4 (different ) HAPPEX-H Q

18 Current and future data on G E + ηg M at forward angle at all Q 2 M + G 0.2 Black line how very imple naive fit. G E 0.1 Data are uggetive of poitive value, but would be unlikely to convince a keptic. 0.0 HAPPEX-III (anticipated) G0 (FORWARD) MAMI A4 A4 (different ) ) HAPPEX-H Q More Happex data are forthcoming at Q 2 = 0.6 GeV 2, (centered at zero). Not hown are upcoming back-angle data from both G0 and A4

19 Current and future data on G E + ηg M at forward angle at all Q 2 M + G 0.2 Black line how very imple naive fit. G E 0.1 Data are uggetive of poitive value, but would be unlikely to convince a keptic. 0.0 HAPPEX-III (anticipated) G0 (FORWARD) MAMI A4 A4 (different ) ) HAPPEX-H New data at Q 2 = 0.6 GeV 2 hould trongly contrain the higher Q 2 region. Q More Happex data are forthcoming at Q 2 = 0.6 GeV 2, (centered at zero). Not hown are upcoming back-angle data from both G0 and A4

20 Two decade of effort ha reulted in atomic-cale control over helicity-correlated beam parameter difference Charge aymmetrie or PITA effect: Bate carbon experiment. Poition difference from lening: teering from lening-type phenomena: Bate carbon experiment. High voltage poitive High voltage negative Poition difference from intrinic phae gradient: due to phae gradient intrinic to the Pockel cell or other optical component, SLAC E158. Poition difference from induced phae gradient: due to coupling of divergence to the Pockel cell tilt: Happex II.

21 Helicity-correlated beam parameter averaged over the Happex II run Charge aymmetry Energy difference x-poition difference x-angle difference y-poition difference y-angle difference The control achieved during the hydrogen run wa unprecedented. Control during the helium run, while more than ufficient, wa limited due to electronic cro-talk problem.

22 Steady progre ha made it poible to conider increaingly challenging parity experiment

23 Steady progre ha made it poible to conider increaingly challenging parity experiment

24 The long legacy of parity experiment poition our community to perform enitive earche for phyic beyond the SM Control of helicity-correlated effect at ppb level. Strong contraint on hadronic effect uch a non-zero trange-quark matrix element Un-precedented figure of merit in term of polarization 2 x luminoity Senitive earche for phyic beyond the SM uch a Qweak (cheduled), and perhap an 11 GeV Møller experiment

25 There are exciting hint indicating phyic beyond Standard Model Meaurement of in 2 θ W agree fairly poorly. g-2 of the muon i 2-3 σ off the SM. Dark matter i unexplained. There are good reaon to expect additional phyic!

26 Electron cattering compliment collider meaurement On the Z pole, A Z will be purely imaginary while A X will likely be real. Accordingly: σ A Z 2 + A X 2 σ A γ + A Z + A X 2 and A RL σ R σ L σ R + σ L A Z RL Away from the Z pole, at higher and lower energie, both amplitude are real and interference can occur. and A RL σ R σ L AZ + A X σ R + σ L A γ (1 + AX 2 ) A Z 2

27 Electron cattering provide acce to very high energy cale δa Z A Z π/λ2 g G f Senitivity to new contact interaction will extend to energy cale Λ on the order of roughly 10 TeV Already E158 provide the mot accurate meaurement of in 2 θ W at low Q 2 Qweak and a poible Møller experiment at 11 GeV provide enitivity that would be tremendouly valuable in the upcoming era of LHC

28 Marciano like to point out that if either the SLD or the bet CERN number were not there, we would have a very different picture right now SLD number, if correct, would tend to favor SUSY CERN number, if correct, would tend to favor modern technicolor

29 Marciano like to point out that if either the SLD or the bet CERN number were not there, we would have a very different picture right now SLD number, if correct, would tend to favor SUSY CERN number, if correct, would tend to favor modern technicolor E158 number, if correct, would tend (ever o lightly) to upport upport the technicolor cenario! Amuing, but hould not be taken eriouly

30 Marciano like to point out that if either the SLD or the bet CERN number were not there, we would have a very different picture right now SLD number, if correct, would tend to favor SUSY CERN number, if correct, would tend to favor modern technicolor Qweak would have greatly improved enitivity to complimentary phyic E158 number, if correct, would tend (ever o lightly) to upport upport the technicolor cenario! Amuing, but hould not be taken eriouly

31 Marciano like to point out that if either the SLD or the bet CERN number were not there, we would have a very different picture right now SLD number, if correct, would tend to favor SUSY CERN number, if correct, would tend to favor modern technicolor E158 number, if correct, would tend (ever o lightly) to upport upport the technicolor cenario! Amuing, but hould not be taken eriouly Qweak would have greatly improved enitivity to complimentary phyic An 11 GeV Møller experiment, the ONLY poibility of reolving outtanding iue here, could be equal to or better than the bet ingle meaurement exiting.

32 Qweak will (and an 11 GeV Møller experiment could) provide powerful probe of SUSY theorie Qweak, by itelf, provide coniderable enitivity to RPV SUSY theorie. Kurylov, Ramey-Mulolf, Su

33 Qweak will (and an 11 GeV Møller experiment could) provide powerful probe of SUSY theorie Qweak, by itelf, provide coniderable enitivity to RPV SUSY theorie. An 11 GeV Møller experiment could provide important enitivity to RPC SUSY theorie that include table particle that could contribute to dark matter. Kurylov, Ramey-Mulolf, Su

34 Qweak apparatu

35 An important perpective on SM tet i to conider a model independent effective Lagrangian Each parity violating aymmetry can then be interpreted to contrain the coefficient C 1u, C 1d, C 2u, and C 2d Qweak i een to put excellent contraint on a linear combination of C 1u and C 1d

36 To learn about ALL the coefficient C 1u, C 1d, C 2u, and C 2d, we need additional type of parity violating emi-leptonic meaurement: PV deep inelatic cattering (PVDIS) Jut a with parity violation in elatic cattering, PVDIS can be ued to tudy of hot of phyic phenomena, from tandard model tet, to charge ymmetry violation, to higher twit effect, and even d/u.

37 Senitivity of PV DIS experiment approved or being conidered at JLab The coefficient C 2u, and C 2d are relatively mall in the tandard model. Thi in fact make them more enitive to certain type of new phyic.

38 Looking toward the future

39 Looking toward the future The role of trange quark i far better undertood today and more information i coming.

40 Looking toward the future The role of trange quark i far better undertood today and more information i coming. Parity violation in electron cattering will provide the ONLY mean for acceing certain important quetion in electroweak phyic until the ILC i built.

41 Looking toward the future The role of trange quark i far better undertood today and more information i coming. Parity violation in electron cattering will provide the ONLY mean for acceing certain important quetion in electroweak phyic until the ILC i built. Both Møller and PVDIS are critical if we are to undertand emi-leptonic interaction.