Low-Energy Accelerators for High Precision Measurements Sebastian Baunack

Transcription

1 Low-Energy Accelerators for High Precision Measurements Sebastian Baunack Johannes Gutenberg-Universität Mainz EINN 2017, Oct Nov 4, 2017 Paphos, Cyprus 1

2 Outline New type of accelerators: ERL High beam currents, thin targets, high luminosities Experiments for Energy Recovering Mode Nucleon form factors Nucleon polarizabilities Searches for particles in the dark sector Experiments for External Beam Mode High preciscion determination of sin²q W Neutron Skin measurement 2

3 Electron accelerator "Classical" recirculating LINAC Multi-turn Electrons are dumped at full energy Example MAMI: E=1.6 GeV, I=100 µa Beam Power P=160 kw Total power needed 2 MW 3

4 Electron accelerator "Classical" recirculating LINAC Multi-turn Electrons are dumped at full energy Higher beam currents? Example MAMI: E=1.6 GeV, I=100 µa Beam Power P=160 kw Total power needed 2 MW Example E=300 MeV, I=10 ma Beam Power P=3 MW (beam dump activation) Total power needed 37 MW (power bill) 4

5 Concept of an ERL Example: Mainz energy recovering superconducting accelerator (MESA) 1.3 GHz c.w. beam Normal conducting injector LINAC Superconducting cavities in recirculation beamline 5

6 Concept of an ERL Example: Mainz energy recovering superconducting accelerator (MESA) 1.3 GHz c.w. beam Normal conducting injector LINAC Superconducting cavities in recirculation beamline ERL mode (Energy recovering mode): 10 ma, 105 MeV unpolarized beam (pseudo internal gas hydrogen target L~10 35 cm -2 s -1 ) Electrons are decelerated after passing the target, giving their energy back to the RF system 6

7 Concept of an ERL Example: Mainz energy recovering superconducting accelerator (MESA) 1.3 GHz c.w. beam Normal conducting injector LINAC Superconducting cavities in recirculation beamline ERL mode (Energy recovering mode): 10 ma, 105 MeV unpolarized beam (pseudo internal gas hydrogen target L~10 35 cm -2 s -1 ) EB mode (External beam): 150 µa, 155 MeV polarized beam (liquid Hydrogen target L~10 39 cm -2 s -1 ) No energy recovering in EB mode 7

8 Past Workshops for ERL Physics PEB Workshop, MIT, March 2013 IEB Workshop, Cornell, June many more: LEPP Apr (Mainz), EIC Workshops,... 8

9 ERL facilities f shielding ERL at Jefferson Lab: Drives the Free-Electron-Laser Current Design Parameter: E=160 MeV, I=10 ma Single Pass Operational since

10 ERL facilities ERL at S-Dalinac at Darmstadt: f shielding Under commissioning, first operation in April 2017 E=22.5 MeV Single Pass First ERL in Germany 10

11 New ERL at Mainz: MESA The Mainz Energy-recovering Superconducting Accelerator 11

12 New ERL at Mainz: MESA 12

13 Experiments in Energy Recovering Mode The MAinz Gas Internal Target EXperiment windowless internal gas target High resolution spectrometers MAGIX: double arm compact design momentum resolution: Δp/p < 10-4 acceptance: ±50 mrad GEM-based focal plane detectors Gas Jet or polarized T-shaped target 1mA ERL beam Simple Design: Quadrupole + Dipole 200 MeV/c maximum momentum Focal plane detector: 50 µm resolution 13

14 Internal Gas Target Approach 1: "Tube Target" Luminosity: ~10 32 cm -2 s -1 (pol.) Target polarization: Injection of polarized hydrogen possible Windows: No target window Scattered particles have to pass tube walls 14

15 Internal Gas Target Approach 2: "Gas Jet Target" Luminosity: ~10 35 cm -2 s -1 Target polarization: No polarization possible Windows: No target window No target wall for scattered particles 15

16 Internal Gas Target First test with MAMI beam in September

17 Focal plane detectors GEM Detector development - 2D Strip readout - 0.7% radiation length - High rate capabilities - Aim for 50 µm resolution 2 Sensitive layers The first centered on the focal plane The second with a sizable lever arm to measure the angle 30 x 120 cm² 17

18 EM Form factor measurements Proton radius puzze e/µ p Pohl et al. [Nature 2010] Antognini et al. [Science 2013] Lamb Shift H : R E = ± fm 7 Difference p Bernauer et al. [A1] (PRC 2014) ep-data & Electronic Spectroscopy: R E = ± fm Codata Electron Scattering on the proton (EM form factors, low Q 2 ) => Form factor measurements at low Q² with MAGIX 18

19 Magnetic Form factor of the proton 19

20 EM Form factor measurements Determination of the magnetic FF of the proton down to Q²=0.005 GeV² Double polarization measurement MAGIX ideally suited: Neglible multiple scattering and energy losses Expected accuracy for the Beam-Target asymmetry of elastic electron scattering from the proton at MESA 20

21 EM Form factor measurements Form factor ratio µ p G Ep /G Mp : Projected accuracy for MAGIX measurement MAGIX projected errors µ p G p E / G p M Bernauer (MAMI 2010) Zhan (JLab 2011) Crawford (Bates 2007) MacLachlan (JLab 2006) Jones (JLab 2006) Punjabi (JLab 2005) Pospischil (MAMI 2001) Dietrich (MAMI 2001) Gayou (JLab 2001) Jones (JLab 2000) MESA projected error Belushkin (Disp. Analysis 2007) Q 2 / (GeV 2 /c 2 ) 21

22 Proton polarizabilities Reaction of nucleon under influence of an EM field <--> Compton scattering provides fundamental information of the nucleon; very sensitive test of theories (H/BχPT, Disp. Rel.). Electric Polarizability: α E1 Magnetic Polarizability: β M1 Spin (Vector) Polarizabilities: γ E1E1, γ M1M1, γ M1E2, γ E1M2 22

23 Proton polarizabilities at MESA Low-energetic proton measured in one of the spectrometers Use dipole close to MAGIX as tagging spectrometer for scattered electron quasi-real photon E g = E MESA E Under investigation: Tagged photon beam at MESA 23

24 Proton polarizabilities at MESA Measurement of photon in final state via dedicated detectors Highly-pressurized active target (TPC) developed by group from St. Petersburg (proton detection) Planned precision of a E1 and b M1 measurements at MESA (proton): Statistical uncertainty: Da E1 =0.07, Db M1 =0.12 Systematical uncertainty: Da E1 =0.11, Db M1 =0.12 Total uncertainty: Da E1 =0.13, Db M1 =

25 Proton polarizabilities at MESA First test with MAMI beam in August 2017 Highly-pressurized active target (TPC) developed by group from St. Petersburg (proton detection) Planned precision of a E1 and b M1 measurements at MESA (proton): Statistical uncertainty: Da E1 =0.07, Db M1 =0.12 Systematical uncertainty: Da E1 =0.11, Db M1 =0.12 Total uncertainty: Da E1 =0.13, Db M1 =

26 Search for a Dark Photon Dark Photon: A New massive force carrier of extra U(1) d gauge group Dark photon LHC Axion W, Z a =e 2 a em Mass [ev] Search for the O(GeV/c 2 ) mass scale in a world-wide effort Could explain large number of astrophysical anomalies Arkani-Hamed et al. (2009) Andreas, Ringwald (2010); Andreas, Niebuhr, Ringwald (2012) Could explain presently seen deviation of 3.6 between (g-2) μ Standard Model prediction and direct (g-2) μ measurement Pospelov(2008) 26

27 Search for a Dark Photon Status year 2010 Coupling allowed parameter range for (g-2) µ explanation 27

28 Search for a Dark Photon Dark Photon Search at MESA: Lepton pair detected with MAGIX spectrometers Lower beam energy to extend search to lower masses Use the high momentum resolution of the spectrometers 28

29 Direct Dark Matter Search (BDX) Electron Scattering on Beam Dump Collimated pair of Dark Matter particles! BDX MESA Beam dump of the P2 experiment 10, µa electrons on target 29

30 Experiments with External Beam Mode Beam energy E=155 MeV, Intensity I=150 µa, Polarization P=85% Thick targets, L=10 39 cm -2 s -1 30

31 The weak mixing angle sin²q W Tree level relations: Electric charge Masses of W and Z Boson Myon decay constant Including radiative corrections: with Absorb universal quantum corrections in an effective, running weak mixing angle: or mit µ as energy scale 31

32 The weak mixing angle sin²q W Running of sin²q W (µ) for a dark Z-Boson with mass of 100 MeV and 200 MeV Mixing parameter are chosen, so that at the same time the anomaly of the magnetic moment of the myon can be explained. Clear sensitivity for the new experiments 32

33 P2: Parity violating asymmetry Polarized electrons R L Detector Target Asymmetry in the cross section of elastic electron-proton scattering for left- and right-handed polarized electrons 33

34 The weak mixing angle sin²q W PDG 2014: Q W (Cs): Atomic parity violation SLAC E158: Møller scattering NuTeV: Neutrino scattering Z-Pole Measurements LEP SLAC Tevatron LHC P2: New measurement at low energy in Mainz with precision comparable to Z-Pole results Sensitivity to BSM Physics at TeV Scale 34

35 Experiments with External Beam Mode The P2 Setup Spectrometer: Superconducting Solenoid Full azimuthal angle coverage 0.6 T magnetic field ~3m diameter Detector: ~100 Fused Silica bars (integrating) +PMT HV-MAPS (Tracking detector) Target: 60 cm liquid hydrogen ~ 3 kw cooling power Target Tracking detectors Integrating detectors 35

36 Magnet spectrometer for the P2 setup Detection of elastically scattered electrons Separation of Møller events in the field of the solenoid Suppression of photons with shielding Find a suitable place for the integrating detectors 36

37 Integrating detectors for the P2 setup Cherenkov-Medium: Fused Silica High transmission in the deep UV radiation hard 37

38 Integrating detectors for the P2 setup Detector development tests ongoing at MAMI beam Most recent test October 2017 Mease yield of photo-electrons as a function of cherenkov material particle energy incidence angle particle type (electron / photon)... 38

39 Tracking detector for the P2 setup Electrons with low momentum: Thin detectors Very high rates: Fast, granular detectors High-voltage monolithic active pixel sensors (HV-MAPS), 50 μm thick 40 x 32 pixels 80 x 103 μm pixel size 9.4 mm² active area 39

40 Measurements with 12 C at P2 Separation of excited states possible Complementary sensitivity for New Physics 40

41 Neutron Skin Measurement PVES on a 208 Pb target: Determination of the Neutron Skin R n 41

42 Summary Energy Recovering LINACs: Intense beams, thin targets, high luminosity New high precision measurements possible Internal beam mode: EM nucleon form factors, nucleon polarizibilities, Dark Photon Searches... External beam mode: High precision measurement of sin²q W, Standard Model tests, Neutron Skin,... 42