An Improved Limit on the Muon Neutrino Mass from Pion Decay in Flight

1. International Summer School on Particle and Nuclear Astrophysics in Nijmegen 2003 An Improved Limit on the Muon Neutrino Mass from Pion Decay in Flight NuMass Experiment Carmen-Miruna Anăstăsoaie Alex Eduardo de Bernardini Sven Lafèbre Martin Vlček

2. Nijmegen’03 What is the aim of the project? NuMass will improve the value of the upper limit of the mass of the muon neutrino. Current limits: m(ne) < 4.35 - 15 eV Tritiumb-decay endpoint < 23 eV TOF spread from SN1987A< 0.5 - 9 eV Doubleb-decay for Majoranan’s m(nm) < 170 keV p -> mn (stoppingp’s) m(nt) < 18.2 MeV Inv. Mass oft -> n + hadrons (e+e- Colliders) improvement by NuMass by order of 20 to m(nm) < 8 keV

3. Nijmegen’03 History of the Muon Neutrino Mass Limit

4. Nijmegen’03 Why is this measurement so important? • verification of theoretical backgrounds- neutrino mass generation mechanism- complementary information to neutrino oscillation results- neutrino decays understanding - chiral left-right symmetry • improvement of the theoretical description of the Fermi constant • understand some loopholes in cosmology- lack of dark matter- limits to the density of Universe • minimal left-right model verification • some propagation phenomena related to supernova pulses • it is, after all, a fundamental constant !

5. Nijmegen’03 Highlights of the experimental technique In a perfectly uniform magnetic field any charged particle returns to origin independent of B or p or angle Uniformity is more important value of B “origin”

6. Nijmegen’03 Highlights of the experimental technique Beam counter p Injection J-veto: restrict early m‘s at large anglesJ-cal: 2nd turn electron id 24 g-2 calorimetersrestrict late decays identify electron bkginitial beam tuning C-veto: restrict incoming p’s decay m p orbit p -> mn observed event by event we will need SEB S1 S2 Trigger Hodoscope

7. Nijmegen’03 Highlights of the experimental technique NuMass will use the existing G-2 Storage Ring in the BNL facilityat Brookhaven with only minor modifications

8. Nijmegen’03 Highlights of the experimental technique S2 Embedded Scintillator:2 mm Prescale Strips Trigger pads S1 Silicon μ-strip Detectors BerylliumDegrader

9. Nijmegen’03 Endpoint structure Expected distance between first pass pion and second pass muon(in mm)

10. Nijmegen’03 Sources of background J-Veto • Beam-gas scatters => vacuum is 10-6 torr • Injected p (27 %) => rejected in embeddedscintilatorsΔT = 7 ns / turn slower • Injected e (12 %) => rejected in J-veto, calorimeter or position, lose 1 MeV / turn • μ → enn => rejected by g-2 calorimeter< 10-4 of good π-μ events • π→ en => rejected by calorimeter in inner J-veto C-Veto g-2 Cal’s S1 S2

11. Nijmegen’03 Advantages of NuMass • run in dedicated mode or in conjuction with K-decay (E949) or MECO experiment • another project may run nearly immediately after our beamtime, there are only minor changes on beam • pure 2 body decay p -> mn, no model dependent nuclear/atomic environment

12. Nijmegen’03 Responsibilities Beamline and Ring BNL SSD and readout electronicsCERN, Minnesota Active Vetoes and Scint Trigger BU, Illinois, Tokyo IT Feedthrus and positioners Tokyo IT, Heidelberg, BNL DAQ and g-2 electronics Minnesota, BU Field Measurements Yale, Heidelberg, BNL Orbital dynamics, Monte Carlo Cornell, BNL, Yale, NYU, Minnesota, BU Analysis The team!

13. Nijmegen’03 Budget $ 770k BNL - modifications on G-2 and SEB - improved sensitivity for the V1 beamline instrumentation - beam time $ 330k CERN, Universities - silicon detectors, degrader, active vetoes - feedthrus, positioners - electronics, DAQ $ 1.1 M TOTAL COST

14. Nijmegen’03 Scheduling • Year 2000build 2-SSD detectors plus removable degrader unitbuild active vetos or simple prototypewrite software for new electronics readout and integrate with g-2 • Year 2001install and test prototype detectors by running parasiticallyunderstand the π-μ orbital parameterstest AGS/beamline modifications for slow extraction to g-2build and test final silicon detector + degrader • Year 2002commission slow extraction to g-2run the experiment parasitically with E 949 • Year 2003dedicated experiment or further parasitic running to completion

15. Nijmegen’03 Thank you for your attention ...

16. Nijmegen’03

17. Nijmegen’03 Neutrino oscillation Neutrino oscillation experimental results are theoretically dependent. Some effects surrounding the standard formulation of neutrino oscillation phenomena: (flavor) quantum number oscillation existence of sterile neutrino chiral oscillation Δm2 DIRECT !!! Neutrino oscillation p -> mn I’m nm understanding of the mixing angles matter effect wave packet description Dirac formulation of neutrino oscillation

18. Nijmegen’03 Neutrino oscillation If you believe atmospheric neutrino result: nm=> ntwith only Dm2~.002 Then this experiment reduces the t neutrino mass limit by 3 orders of magnitude!

19. Nijmegen’03 T0 J-Veto Inflector Flash Counter Pion on orbit Muon hits J-Vetoon 1st turn pion 2nd time around collimator Degrader pion => pion residual profile

20. Nijmegen’03 Some background configurations p -> e n p -> mn J-Calorimeter g-2 Calorimeters m -> enn 5 mm endpt (q=70 MeV/c) SR shrinks it 2 mm

21. Nijmegen’03 Cross section of g-2 superconducting magnet

22. Nijmegen’03 Cross section of the field Contours every 1 ppm of field gradient represents lines every 1.5 μTesla Magnetic field is 1.45 Tesla

23. Nijmegen’03 Running Time 5% of SEB beam => 492 hrs (crystal extr. eff.) Proposed Parasitic Running with AGS Crystal Extraction E949 Running Conditions 25 Gev protons70 TP in a 4.1 s spill / 6.4 s cycle E952 Parameters2.8 x 106p+into g-2 ring/TP5.4 x 1012p+for an 8 keV result Triggers Offline Entering Ring Detector p-pp-m (p-m)+vetoes 8 x 106 part/s 1 x 106 part/s 1.8 x 105 s-1 910 s-1 42 s-1 400 Hz/strip 55 ms/SSD 11 ms/SSD 100 MB/s 0.5 MB/s Instantaneous rates (100% extr. eff.) Prescale in trigger