E XPERIMENTS WITH I NTERNAL T ARGETS AT THE M AINZ E NERGY -R ECOVERING S UPERCONDUCTING A CCELERATOR Harald Merkel Johannes Gutenberg-Universit¨ at Mainz 54 th International Winter Meeting on Nuclear Physics Bormio (Italy), January 27 th, 2016 The MESA Accelerator MAGIX High resolution magnetic spectrometers Internal targets: Gas Jet Target or Polarized Target Physics program Magnetic radius of the proton Astropyhsical S-Factor Few body physics Search for exotic particles Summary
MESA - Mainz Energy Recovery Superconducing Acclerator Super-conducting, recirculating LINAC Energy of up to 155 MeV Operation for external targets, 1 mA, polarized beam Operation in ENERGY RECOVERY MODE (up to 105 MeV) Recirculating with λ / 2 phase shift in last return path Deceleration in cavities recovers energy from the beam ⇒ High beam current (up to 10 mA) Large fraction of the beam can be used for an INTERNAL TARGET ...funded, under construction! Harald Merkel, Bormio 2016 2/19
Magix - Design Considerations Using the full power of the MESA beam quality Beam intensity ⇒ High count rate capability (MHz) Nuclear Physics: Separate energy levels at 100 MeV at 100keV distance ⇒ momentum resolution δ p p < 10 − 4 Precision measurement of electron scattering cross sections proportional to Mott cross section d σ d Ω ≈ 1 1 Q 4 ≈ sin 4 θ / 2 ⇒ angular resolution δθ < 0 . 05 ◦ Low energetic particles ( e , p , below π threshold) Negligible energy loss in window-less gas target Vacuum until first detector layer Excellent position detection in first layer, modest angular detection later ⇒ Focussing spectrometers Harald Merkel, Bormio 2016 3/19
Magix - Optics 2500 3500 B [T] 2000 0.7 0.525 3000 0.35 0.175 2500 1500 0 path length off central beam [mm] x [mm] 2000 1000 1500 1000 500 500 0 0 60 50 40 30 20 10 0 -10 -20 -30 -40 -50 -60 y [mm] 0 500 1000 1500 2000 2500 z [mm] scale 1:180 Harald Merkel, Bormio 2016 4/19
Magix Harald Merkel, Bormio 2016 5/19
Magix - Targets 1. Polarized Target Polarized Hydrogen target Flow is limited by polarizator (Laser driven/Atomic beam) Polarized Gas L = 2 × 10 31 s − 1 cm − 2 Luminosities of up to | � P e | ≈ 80% Polarization Beam T arget cell 2. Gas Jet Target Hypersonic gas jet by Laval nozzle Gas jet caught mbar → 10 − 11 mbar Expensive part: Pumping system Beam quality: narrow flow delimiters L = 10 36 s − 1 cm − 2 Luminosities of up to at 10 mA Harald Merkel, Bormio 2016 6/19
Physics Program at Magix Physics Program to employ the strenghtes of MESA and Magix High beam intensity ↔ low target density Excellent beam quality ⇒ Precision physics High degree of beam/target polarization Tuneable to very low energies Selected Examples: Magnetic Radius Tests of ab-initio Calulations in Few-Body Physics Astrophysical S-Factors Search for exotic particles: Search for Dark Photons Invisible Decay of Dark Photons Dark matter beam Harald Merkel, Bormio 2016 7/19
Magnetic Radius of the Proton Magnetic Radius from limit Q 2 → 0 Suppressed by τ = Q 2 p in cross section 4 m 2 � d σ � d σ 1 ε G 2 E ( Q 2 )+ τ G 2 M ( Q 2 ) � � = d Ω e d Ω e ε ( 1 + τ ) Mott p p | > 300 MeV Beam-Recoil polarization is limited by proton recoil momentum | � c Beam-Target polarization: A ( θ ∗ , φ ∗ ) = A I sin θ ∗ cos φ ∗ + A S cos θ ∗ τ ( 1 + τ ) tan θ G E G M � A I = − 2 τ + 2 τ ( 1 + τ ) tan 2 θ � � G 2 G 2 2 E + M 2 � G 2 1 + τ +( 1 + τ ) 2 tan 2 θ 2 tan θ M A S = − 2 τ τ + 2 τ ( 1 + τ ) tan 2 θ G 2 � � G 2 2 E + M 2 φ ∗ = 0 � A ⊥ = A l ∼ G E ⇒ θ ∗ = 0 , π A s G M 2 Harald Merkel, Bormio 2016 8/19
Magnetic Radius of the Proton - Asymmtry 0 Beam Energy E = 100 MeV 0 Beam polarization P = 80% beam -10 Target polarization P = 75% T Time per setting t = 10d 31 [%] -1 -2 -20 Luminosity L= 2 10 s cm × Asymmetry A -30 Asymmetry (Calc) -40 o Setting = 42.0 θ e o Setting = 61.8 θ e -50 o Setting = 79.3 θ e o Setting = 96.9 θ e o Setting = 116.2 -60 θ e o Setting = 141.8 θ e -70 -0.03 -0.025 -0.02 -0.015 -0.01 -0.005 2 2 2 Photon Virtuality q [GeV /c ] (Conservative) assumptions for target ≈ Blast target Statistical error only (systematic error should be small!) Harald Merkel, Bormio 2016 9/19
Magnetic Radius of the Proton - Errors 1.1 1 – Bernauer (MAMI 2010) 0.9 M Zhan (JLab 2011) E /G p Crawford (Bates 2007) MacLachlan (JLab 2006) µ p G p Jones (JLab 2006) Punjabi (JLab 2005) 0.8 Pospischil (MAMI 2001) Dietrich (MAMI 2001) Gayou (JLab 2001) Jones (JLab 2000) MESA projected error 0.7 — Belushkin (Disp. Analysis 2007) 0.6 0.01 0.1 1 10 Q 2 / (GeV 2 /c 2 ) Harald Merkel, Bormio 2016 10/19
Tests of ab-initio Calulations in Few-Body Physics Ab initio calculations e.g. with Effective Field Theory Consistent chiral expansion of elementary NN-interaction Consistent expansion of Few-Body-Systems Very promising, but How can we test this? Harald Merkel, Bormio 2016 11/19
How can we test Ab-Initio-Calculations? Challenge for theory: Reaction dynamics Possible solution: Use EFT input for potentials Faddeev Calculations for dynamics (J. Golak, H. Witała, ...) Prediction of dynamic observables Promising: Polarization observables Challenge for experiments: Low Momentum Region Needed: High resolution (separate excited states!) Low momentum (use gas targets!) High luminosity (in spite of gas target!) High degrees of beam and target polarization (in spite of high luminosity!) ⇒ Magix @ MESA Harald Merkel, Bormio 2016 12/19
Astrophysical S-Factor for α ( 12 C , 16 O ) γ σ ≈ 10 − 17 barn ← He-Burning How to overcome limits: 1. Timereversal (enhancement by factor 10 due to spin weight): γ + 16 O → 12 C + α 2. Covering the Threshold: Electroproduction in limit Q 2 → 0 e + 16 O → e ′ + 12 C + α γ ∗ + 16 O → 12 C + α ⇔ Electron has large momentum, but virtual photon energy goes to zero! 3. Detection of slow recoil α ⇒ gas target, recoil detector Harald Merkel, Bormio 2016 13/19
Search for exotic particles: Dark Photons (a) (b) γ' γ' e − e − e − e − Z Z Z Z Dark photon: Force carrier of the Dark Sector Radiative production e + Z → e + Z + γ ′ → e + + e − (detected in Magix) -2 10 KLOE 2014 KLOE 2013 ε B A B AR (g-2) 2009 WASA e APEX ± σ HADES (g-2) 2 µ B A B AR PHENIX A1 favored 2014 NA48/2 -3 10 E774 E141 -4 10 MESA -2 -1 10 10 2 m [GeV/c ] γ ' Harald Merkel, Bormio 2016 14/19
Beam-Dump Experiments: Motivation SuperCDMS Soudan CDMS-lite SuperCDMS Soudan Low Threshold XENON 10 S2 (2013) 10 � 39 CDMS-II Ge Low Threshold (2011) 10 � 3 CoGeNT PICO250-C3F8 (2012) 10 � 40 10 � 4 CDMS Si (2013) SIMPLE (2012) 10 � 41 10 � 5 WIMP � nucleon cross section � cm 2 � ) 2 1 0 WIMP � nucleon cross section � pb � 2 DAMA ( P P U ZEPLIN-III (2012) O C 10 � 42 CRESST 10 � 6 ) 9 0 0 2 ( e SuperCDMS G I I S SuperCDMS Soudan M D C 1 ) 0 1 2 S ( 10 � 43 S 10 � 7 E I W E L D E 2 ) 1 0 SNOLAB 2 ( 0 DarkSide 50 0 N 1 n E U o n e X T 10 � 44 R 10 � 8 I N LUX O PICO250-CF3I 7 Be C T C A T E O H S R E E N T R Neutrinos I N G 8 B 10 � 9 10 � 45 Xenon1T Neutrinos DEAP3600 DarkSide G2 10 � 46 10 � 10 Z L 10 � 47 10 � 11 (Green&ovals)&Asymmetric&DM&& (Violet&oval)&Magne7c&DM& G I N R E T T A (Blue&oval)&Extra&dimensions&& C S s 10 � 48 R E N T o 10 � 12 n i r H E u t e N (Red&circle)&SUSY&MSSM& O C B O N S I N R D T U d E n &&&&&MSSM:&Pure&Higgsino&& N a c r i e h p s 10 � 49 o 10 � 13 m &&&&&MSSM:&A&funnel& A t &&&&&MSSM:&BinoEstop&coannihila7on& &&&&&MSSM:&BinoEsquark&coannihila7on& 10 � 50 10 � 14 & 1 10 100 1000 10 4 WIMP Mass � GeV � c 2 � Direct detection experiments: No clear signal yet Limit of sensitivity (solar ν background) will be reached soon Lower masses ( i.e. low recoil energy) not accessible P . Cushman, et al. , arXiv:1310.8327 Harald Merkel, Bormio 2016 15/19
Beam-Dump Experiments: Idea 10 m 10 m Dirt e − χ Beam Dump Detector Production in beam dump, e.g. via pair production e − χ e − A 0 χ Z We now have a Dark Matter Beam! Dark Matter particles have enough recoil energy! Detection with simple detector, e.g. scintillator cube ... or with sophisticated DM Detector ... Harald Merkel, Bormio 2016 16/19
FLUKA Simulation Neutrons can be shielded Below pion threshold: negligible ν background Clean conditions, detailed layout of hall needed for further design Harald Merkel, Bormio 2016 17/19
Magix Sensitivity Reasonable sensitivity for low mass region Multidimensional plot: Assumptions for dark photon mass, m χ Calculations: G. Krnjaic Harald Merkel, Bormio 2016 18/19
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