The P2 Experiment at MESA

Transcription

1 The P2 Experiment at MESA Sebastian Baunack Johannes utenberg-universität Mainz Intense Electron Beams Workshop June 17-19, 2015 Cornell University

2 External target experiments: Challenges and opportunities Sebastian Baunack Johannes utenberg-universität Mainz Intense Electron Beams Workshop June 17-19, 2015 Cornell University

3 External target experiments Opportunities: Measurement of very small asymmetries with parity violating electron scattering Challenges: Technique, form factor input, targets Studies for the upcoming P2 experiment at MESA

4 Concept of an ERL - MAMI-Shutdown: Clearing of MESA Hall-2 - Moving of MAMI beamline instrumentation - Erection of shielding Mainz energy recovering superconducting accelerator 1.3 Hz c.w. beam Normal conducting injector LINAC Superconducting cavities in recirculation beamline ERL mode (Energy recovering mode): 10 ma, 100 MeV unpolarized beam (pseudo internal gas hydrogen target L~10 35 cm -2 s -1 ) EB mode (External beam): 300 µa, 150 MeV polarized beam (liquid Hydrogen target L~10 39 cm -2 s -1 )

5 Concept of an ERL - MAMI-Shutdown: Clearing of MESA Hall-2 - Moving of MAMI beamline instrumentation - Erection of shielding Mainz energy recovering superconducting accelerator 1.3 Hz c.w. beam Normal conducting injector LINAC Superconducting cavities in recirculation beamline Internal target ERL mode (Energy recovering mode): 10 ma, 100 MeV unpolarized beam (pseudo internal gas hydrogen target L~10 35 cm -2 s -1 ) Electrons that pass the internal target are decelerated and their energy recovered: Very intense electron beams possible! EB mode (External beam): 300 µa, 150 MeV polarized beam (liquid Hydrogen target L~10 39 cm -2 s -1 )

6 Concept of an ERL - MAMI-Shutdown: Clearing of MESA Hall-2 - Moving of MAMI beamline instrumentation - Erection of shielding Mainz energy recovering superconducting accelerator 1.3 Hz c.w. beam Normal conducting injector LINAC Superconducting cavities in recirculation beamline ERL mode (Energy recovering mode): 10 ma, 100 MeV unpolarized beam (pseudo internal gas hydrogen target L~10 35 cm -2 s -1 ) External target EB mode (External beam): 300 µa, 150 MeV polarized beam (liquid Hydrogen target L~10 39 cm -2 s -1 ) Target is too thick: Electrons can't be decelerated and go directly into a beam dump Very high luminosity possible!

7 Parity violating electron scattering

8 Parity violating electron scattering

9 Presence Forward angle PV experiments Past Future

10 Forward angle PV experiments Experiment Luminosity (10 38 s -1 cm -2 ) Target cooling power (kw) HAPPEX A Qweak P Moller

11 Forward angle PV experiments Experiment Luminosity (10 38 s -1 cm -2 ) Target cooling power (kw) HAPPEX A Qweak P Moller Opportunity! Measure tiny asymmetries in ppb range

12 Forward angle PV experiments Experiment Luminosity (10 38 s -1 cm -2 ) Target cooling power (kw) HAPPEX A Qweak P Moller Opportunity! Measure tiny asymmetries in ppb range Challenge! Huge energy deposition in the hydrogen target

13 PVES and the weak mixing angle sin²q W (µ) h= s p s p +: h=+1 : h= 1 detector R ± long. polarized beam electrons proton - target At low momentum transfer: Q² 0: A PV = F Q π α (Q W ( p) F (Q 2 )) Weak charge of the proton: Q w ( p)=1 4sin 2 (θ W )(μ) Proton structure: F (Q 2 )=F EM (Q 2 )+F Axial (Q 2 )+F Strange (Q 2 )

14 PVES and the weak mixing angle sin²q W (µ) h= s p s p +: h=+1 : h= 1 detector R ± long. polarized beam electrons proton - target At low momentum transfer: Q² 0: A PV = F Q π α (Q W ( p) F (Q 2 )) Weak charge of the proton: Q w ( p)=1 4sin 2 (θ W )(μ) Proton structure: F (Q 2 )=F EM (Q 2 )+F Axial (Q 2 )+F Strange (Q 2 ) Weak mixing angle

15 The weak mixing angle / standard model relations

16 The weak mixing angle sin²q W (µ) Measurements: Atomic parity violation Neutrino scattering LEP and SLAC Tevatron Q weak (finished data taking) Moller (planned) P2 (planned)

17 Sensitivity to a new Physics Example: Dark Z boson H. Davoudiasl, H. S. Lee and W. J. Marciano, Phys. Rev. D 89 (2014) 9,

18 DA PV (ppm) A PV (ppm) Finding a scattering angle for an experiment A PV Scattering angle Contributions to DA PV => Forward scattering angles preferred! Scattering angle

19 Choice of kinematics for the P2 experiment

20 Choice of kinematics for the P2 experiment

21 Choice of kinematics for the P2 experiment

22 Beam fluctuations Uncorrelated beam fluctuations: Larger uncertainty Helicity correlated beam fluctuations: Systematic uncertainty

23 Helicity correlated beam fluctuations Example: Different positions of the beam for the helicities "+" and "-" Different scattering angles Different cross sections Different solid angles Different scattering rates => False asymmetries

24 Beam stabilization at MAMI/A4 Analog feedback loops Helicity flip 50 Hz Beam energy 315 MeV

25 Helicity correlated beam fluctuations Which uncertainty contribution to A PV would be realistic with the existing MAMI technique after hours of data taking? Requirement from the experiment: DA<0.1 ppb Helicity correlated beam parameter Expected average after hours Uncertainty contribution after hours Beam intensity asymmetry 23 ppb 11 ppb Beam position difference 7 nm 5 ppb Beam energy difference 0.04 ev < 0.1 ppb

26 Helicity correlated beam fluctuations Which uncertainty contribution to A PV would be realistic with the existing MAMI technique after hours of data taking? Requirement from the experiment: DA<0.1 ppb Helicity correlated beam parameter Expected average after hours Uncertainty contribution after hours Beam intensity asymmetry 23 ppb 11 ppb Beam position difference 7 nm 5 ppb Beam energy difference 0.04 ev < 0.1 ppb J

27 Helicity correlated beam fluctuations Which uncertainty contribution to A PV would be realistic with the existing MAMI technique after hours of data taking? Requirement from the experiment: DA<0.1 ppb Helicity correlated beam parameter Expected average after hours Uncertainty contribution after hours Beam intensity asymmetry 23 ppb 11 ppb Beam position difference 7 nm 5 ppb Beam energy difference 0.04 ev < 0.1 ppb J L

28 Helicity correlated beam fluctuations Which uncertainty contribution to A PV would be realistic with the existing MAMI technique after hours of data taking? Requirement from the experiment: DA<0.1 ppb Helicity correlated beam parameter Expected average after hours Uncertainty contribution after hours Beam intensity asymmetry 23 ppb 11 ppb Beam position difference 7 nm 5 ppb Beam energy difference 0.04 ev < 0.1 ppb J L L

29 Helicity correlated beam fluctuations Which uncertainty contribution to A PV would be realistic with the existing MAMI technique after hours of data taking? Requirement from the experiment: DA<0.1 ppb Helicity correlated beam parameter Expected average after hours Uncertainty contribution after hours Beam intensity asymmetry 23 ppb 11 ppb Beam position difference 7 nm 5 ppb Beam energy difference 0.04 ev < 0.1 ppb J Improvements for the new accelerator MESA: Digital feedback loops (FPA based) Stabilizations directly on the beam differences / asymmetries Increased bandwidth / sensitivity for the beam monitors L L

30 Helicity correlated beam fluctuations Test of new feedback techniques already started with 180 MeV beam at MAMI

31 Installations at MAMI Test of new feedback techniques already started with 180 MeV beam at MAMI

32 Choice of kinematics for the P2 experiment

33 2 2 2 p M p E n M p M n E p E EM Q F ) (1 1 ) 4 (1 p M p E A p M z axial s Q F p M p E s M p M s E p E Strange Q F p M Q tan Form factor input A PV = F Q π α (Q W ( p) F (Q 2 )) Parity violating asymmetry Vector coupling without strangenes Axial coupling Vector coupling, strangeness contribution

34 2 2 2 p M p E n M p M n E p E EM Q F ) (1 1 ) 4 (1 p M p E A p M z axial s Q F p M p E s M p M s E p E Strange Q F p M Q tan Form factor input A PV = F Q π α (Q W ( p) F (Q 2 )) Parity violating asymmetry Vector coupling without strangenes Axial coupling Vector coupling, strangeness contribution Largest contributions to the uncertainty

35 Experimental data for M s SAMPLE: D. T. Spayde et al., Phys.Rev.Lett. 84 (2000) Happex: A. Acha et al., Phys.Rev.Lett. 98 (2007) : D. S. Armstrong et al., Phys.Rev.Lett. 95 (2005) D. Androic et al., Phys.Rev.Lett. 95 (2010) A4: F. E. Maas et al., Phys.Rev.Lett. 93 (2004) S. Baunack et al., Phys.Rev.Lett. 102 (2009)

36 Experimental data for A SAMPLE: T. M. Ito et al., Phys.Rev.Lett. 92 (2004) : D. S. Armstrong et al., Phys.Rev.Lett. 95 (2005) D. Androic et al., Phys.Rev.Lett. 95 (2005) A4: Paper in progress A4-IV: about 700 hours deuterium data on tape

37 Can we measure M s and A with better precision? Sketch of P2 main experiment: Liquid hydrogen target Elastic ep-scattering DQ = 20 Measurement time: T= h Luminosity L= s cm²

38 P2 back angle measurement! Back angle measurements: Determination of M s and A

39 P2 back angle measurement Imagine to place an A4-like detector (DW=0.63 sr, 140 Q 150 ) into the P2 setup: A PV 7.5 ppm Parameter P2 back angle experiment Integrated luminosity fb -1 DA stat = 0.03 ppm HC correlated false asymmetries DA HC = ppm Polarimetry DP = 0.5% DA Pol = 0.04 ppm Uncertainty in the measured asymmetry DA tot = 0.05 ppm ( 0.7 %) Ideal solution: Separate measurements with hydrogen and deuterium target

40 Possible uncertainties of A and M s with P2 back angle measurement Q²=0.06 ev² Numerical determination of precision Choose randomly EM form factors and asymmetries according to their uncertainties and calculate A and M s Correlation of electromagnetic form factors input taken into account D A 0.05 D s 0. M 04

41 Measurements with other targets at P2

42 Sensitivity of the weak charges to New Physics

43 12 C measurement at P2

44 12 C measurement at P2

45 P2 concept: Solenoid spectrometer

46 P2 concept: Solenoid spectrometer Full EANT4 simulation: Interface with CAD program (CATIA) Tests of various setups See talk of D. Becker for details

47 Detector development for P2

48 Prototype detector tests at MAMI

49 Prototype detector tests at MAMI

50 Summary Parity violating electron scattering: Ideal application for external target experiments Hydrogen target: Determination of the weak mixing angle at low Q² with high precision Technical challenges: Due to high rates and small asymmetries Additional benefits: Measurement of A and M s, carbon target P2: Measurement of weak mixing angle at MESA, work in progress

51 Example: P.E. yield for different polishings and scattering angles