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VLADD

This seminar discusses the theoretical motivation and design of the VLADD detector for detecting invisible decays of positronium, a bound state of an electron and positron, which could provide evidence for the existence of extra dimensions.

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VLADD

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  1. VLADD VLAnd extra Dimensions Detector H. Ray, R. V. de Water (LANL) P. Vetter (LBL) (LANL : G. Garvey, B. Louis, G. Mills) H. Ray (P-25) Wednesday Seminar

  2. Documentation • TDR (extensive calculations included) • References from TDR • LDRD/ER proposal • All talks VLADD related http://home.fnal.gov/~hray = work in progress H. Ray (P-25) Wednesday Seminar

  3. Outline • Intro to Positronium • Theoretical Motivation • VLADD Detector Design • Event Selection • Some Numbers • Future Plans See P. Vetters Jan. 25th LANL talk on web H. Ray (P-25) Wednesday Seminar

  4. Positronium H. Ray (P-25) Wednesday Seminar

  5. Positronium • Bound state of an electron and positron • no nuclear structure • Bound + annihilates through EM interactions http://positrons.physics.lsa.umich.edu • 2 ground levels : spin 0 and spin 1 • Spin 0 (1S0) : parapositronium (pPs), singlet state (|0,0>) •  = 0.125 ns • Spin 1 (3S1) : orthopositronium (oPs), triplet state (|1,1>, |1,0>, |1,-1>) •  = 142.074 ns (vacuum) H. Ray (P-25) Wednesday Seminar

  6. Decay of States • SM couplings : to , - pair • pPs - pair : suppressed by (m/me)2 • oPs - pair ≈ [G2F3m5e / 242][14sin2w]2 • ≈ 10-18 BR(oPs 3 ) •  only decays to photons • Eigenstate of C operator • oPs = odd #  (3) only • pPs = even #  (2) only • Additional  pair emission suppressed by power of 2 • Mixing/pickoff can occur between states C |2S+1Lj> = -1L+S |2S+1Lj> H. Ray (P-25) Wednesday Seminar

  7. oPs Energy Spectrum 1.5 1.4 0.8 0.4 Ps total E ~1.022 MeV H. Ray (P-25) Wednesday Seminar

  8. Why Search for Invisible oPs Decays? H. Ray (P-25) Wednesday Seminar

  9. Our brane graviton g e+ e- BULK Review : R-S Extra-D hep-th/9905221 : R&S hep-th/9906064 : R&S • Real world described using warped geometry • defines universe as 5-D anti-de Sitter space, two 4-D branes • all elementary particles with gauge numbers localized on SM brane • Gravity confined to Planck scale physics brane • SM particles without gauge numbers couple to graviton, can “disappear” from our brane Ps  *, * couples to graviton H. Ray (P-25) Wednesday Seminar

  10. How might extra dimensions be detected? Discover massive KK modes at particle accelerators • heavy bosons (new particle signature) • heavy gravitons (missing energy signature) (Substantial Std. Model background) Maybe the KK modes are stable particles and are dark matter • dark matter, WIMP searches Gravity behaves differently at short range • fancy Cavendish balances Mass-energy itself is unstable in some scenarios bulk modes of particles allow tunneling off our brane • Total calorimetry experiment to search for energy disappearance H. Ray (P-25) Wednesday Seminar

  11. oPs”Nothing” Rate Ps has no quantum #s, longest lived ferm-antiferm bound state Br(oPsnothing) ≈ 3·104 (moPs / k) 2 Bound on k from LEP data on Z nothing : k 2 TeV Solve gauge hierarchy with extra infinite d, k ≤ O(10) TeV 4 ·10-9 Br(oPs”nothing”)  O(10-10) Dubovsky, Rubakov, Tinyakov, PRD 62, 105011 Gninenko, Krasnikov, Rubbia, PRD 67, 075012 H. Ray (P-25) Wednesday Seminar

  12. A search for (o-Ps -> “nothing”) at a level below 1e-10 is appealing • Positive result suggests Randall-Sundrum extra dimensions are correct • Null result eliminates broad class of extra dimensional theory • Complementary to accelerator searches for KK mode particles or KK graviton missing energy: • If accelerators detect KK modes, this does not distinguish among a broad range of extra dimension theories. Need lots of data on the spectrum of KK modes. • Accelerator searches could get unlucky. Little theoretical preference right now. H. Ray (P-25) Wednesday Seminar

  13. Caveat • Focus here on extra-dimensions • In reality missing energy signature from oPs is forbidden, could be the result of anything! • Fractional charged particles (GUTs) • SSM light EW vector boson • Non-zero  magnetic moment H. Ray (P-25) Wednesday Seminar

  14. Previous oPs-> “Nothing” Experiments H. Ray (P-25) Wednesday Seminar

  15. Previous Searches () • 1989 : Atoyan, Gninenko, Razin, Ryabov • BR < 5.8 x 10-4 (90% CL) • 1993 : Mitsui, Fujimoto, Asai, et. Al. • BR < 2.8 x 10-6 (90% CL) • 2003 : proposal by Badertscher, Gninenko, Rubbia, et. Al. • expect backgrounds from fake positron tagging • Cosmic rays, environmental activity, etc.. Enter VLADD ……. H. Ray (P-25) Wednesday Seminar

  16. VLADD H. Ray (P-25) Wednesday Seminar

  17. Two ways to search for a new decay counting lifetime VLADD is a counting experiment, not a lifetime measurement! VLADD is not the final goal - this is a demonstration experiment H. Ray (P-25) Wednesday Seminar

  18. Atoyan et al. 1989 10 -4 Excluded by BBN 10 -5 VLADD Mitsui et al. 1993 10 -6 ETH Zurich, proposed Milicharged particles, Mirror matter 10 -7 Branching ratio (o-Ps -> “invisible”) 10 -8 LBNL/LLNL 1st design proposal Limit from width of (Z0 -> invisible) 10 -9 Allowed region for (o-Ps->g->extra dimensions) final goal 10 -10 Triviality: extra dimension physics happens at > 10 TeV Neutrino magnetic moment (o-Ps -> nn) 10 -18 H. Ray (P-25) Wednesday Seminar

  19. Overview • Positron source • Scintillator layers to trigger on positron emission, start data collection • TPC to identify positron, separate electron background • SiO2 aerogel for creation of Ps • Scintillating container for “innards” • VLAND tank filled with scintillating mineral oil, PMTs • B field (0.0016 Tesla) H. Ray (P-25) Wednesday Seminar

  20. Overview PMTs e+ Cerenkov cones e- Sodium-22 H. Ray (P-25) Wednesday Seminar

  21. Sodium-22 • Half-life = 2.605 years • e+ max KE of 0.55 MeV • Source placed on inner surface of scint. Layer • LANL is manufacturer and distributer of 22Na H. Ray (P-25) Wednesday Seminar

  22. Scintillator Trigger • Two cylindrical shells of plastic scintillator, located in TPC hollow core • Each layer has own PMT readout • Bicron BC-404 • decay time of 2 ns • peak emission @ 408 nm • < 100 keV X-rays • Alpha, beta particles H. Ray (P-25) Wednesday Seminar

  23. TPC Outer field cage e+ e- created in gas Inner field cage Endcap - anode, traditionally wire chamber B E Gas filled chamber HV central membrane H. Ray (P-25) Wednesday Seminar

  24. TPC • Known Specs • Inner radius ~0.5 cm, outer ~6 cm • B field of 0.0016 Tesla, E field ~ few hundred V/cm (typical) • Gas choice : ArCF4C2H6 (80:10:10) = ~9cm/s in 0 T, 400 V/cm • Need ~0.1 MeV to 0.55 MeV K.E. e+ to pass through (90% of all sodium-22 particles) • R&D Vital • Thin, sturdy walls, VERY LOW dE/dx • Cu = 0.16 MeV/cm, Al = 0.6 MeV/cm, Kapton = 1.28 MeV/cm, Mylar = 1.33 MeV/cm, Nomex = 0.15 MeV/cm • Outer wall faces vacuum or dry nitrogen • GEM readout + electronics This is where R&D funds come in .. H. Ray (P-25) Wednesday Seminar

  25. GEM Technology Cathode ~3 mm conversion and drift region 1 GEM drifting ele guided into holes ~1mm induction gap PCB w/ pick-up strips (anode) • pitch of 140 m • ~100 m thick Pot. Diff (400-500V) between electrodes • 2 sided Cu foil • diameters 70 m Amplification!! each hole = indivdual prop. counter H. Ray (P-25) Wednesday Seminar

  26. GEM Technology Total gain : 102 (single) - 105 (triple) www.lnf.infn.it/seminars/talks/murtas_28_11_02.pdf H. Ray (P-25) Wednesday Seminar

  27. GEM Technology • GEM qualities • Ion-feedback reduced • Small pitch between holes • ExB effects reduced • All readout geom possible • No ion tail = fast signal • More stable than wires • Separate gas amplification and readout geometries • Can withstand high radiation flux • GEMs introduced @ CERN, 1996 • HE physics, dosimetry, thermal n detect., medical imaging, X-ray burst detection, polarization detection ….. • Period of intensive research/use of GEMs/GEM TPCs • GEM-TPCs : Karlsruhe, CERN, B-factory LANL needs to become a part of this technology! H. Ray (P-25) Wednesday Seminar

  28. SiO2 Aerogel • Particles 2-5 nm diameter, pores 2 to > 50 nm diameter • Density 0.1 - 0.5 g/cm3 • ~ 5% solid, 95% free space • b/c oPs pickoff (shortened lifetime) in O2, need vacuum or dry nitrogen • Cooked @ 800 C • Doping possible R&D H. Ray (P-25) Wednesday Seminar

  29. Containment Vessel • Porous nature of aerogel = must protect from mineral oil • Create container to surround entire source/scint/tpc/aerogel package • Construct from plastic scintillator, use to measure “lost” photons from Ps decay • Bicron BC-408 • 0.1 MeV - 5 MeV , fast neutrons, charged particles (cosmic rays, muons, protons, etc) • Decay time 2.1 ns • Peak emission @ 425 nm H. Ray (P-25) Wednesday Seminar

  30. VLAND Complete construction March/05 • 2 meter diameter x 2 meter high tank • 1700 gal. b-PBD mineral oil • ~10K /MeV, ~7% E/E • 50 8” PMTs • 12% coverage • Precision electronics (LSND) • Reconstruct time, position, direction, E of event Use alone to detect n,  from rad mat. + Rad = defeat attempts to shield rad mat. H. Ray (P-25) Wednesday Seminar

  31. VLAND Tank Dude, where are the Extra-ds??? H. Ray (P-25) Wednesday Seminar

  32. B-Field Max separation • Need a small B field (0.0016 Tesla) to separate e+ from e- • For e+ with KE of 0.001 MeV, radius of curvature of 6.675 cm, sep between e+, e- = 0.1856 cm • External or mag? • @ TPC resolution of 200 m, resolve e+, e- w/ KE 8.1 MeV |S> = 1 |0,0> - 0.0002205 |1,0> |T> = 0.0002205 |0,0> + 1 |1,0> H. Ray (P-25) Wednesday Seminar

  33. 12 cm long 6 cm outer radius Positron source (22Na) 0.5 cm inner radius Two scintillator layers, each read out by its own PMT H. Ray (P-25) Wednesday Seminar

  34. ~6 mm thick layer of SiO2 aerogel Positron source (22Na) Two scintillator layers, each read out by its own PMT H. Ray (P-25) Wednesday Seminar

  35. Scintillating plastic vessel Positron source (22Na) Two scintillator layers, each read out by its own PMT H. Ray (P-25) Wednesday Seminar

  36. 2 m long 1 m radius Typical PMTs VLANDtank ~13 cm long ~13 cm high VLADD H. Ray (P-25) Wednesday Seminar

  37. The Numbers H. Ray (P-25) Wednesday Seminar

  38. Event Selection On-line • Trigger on inner scintillator coincidence in window of 1-2 ns • Collect all info in detector for 3 s window • Look for track in TPC identified as good e+ • Curvature = positively charged particle • proper momentum, energy for Na decay • Track going from Na into aerogel • Not exiting endcap • Look for 1.275 MeV in scint. container, tank from Na decay emitted 3.2 ps after e+ • Cut on arrival times of other  in tank Off-line H. Ray (P-25) Wednesday Seminar

  39. Rate Calculation • 0.1 Curie = 3.2 x 108 decays/day (~3700/s) • Reductions to rate : • Loss of e+ in scint layers : 2% • Geom of TPC and scint layers : loss of 0.17% • Eff. of scint layers : 80% • Momentum || to B field : loss of 1.6% • Eff. of TPC : 80% • Loss of  in TPC shell/dead material • Creation rate of oPs in aerogel : 20% • Conversion due to B field : loss of 0% • Overlap with cosmic events : loss of 0.3% R&D! H. Ray (P-25) Wednesday Seminar

  40. Detection Efficiency • % photons absorbed/interact in plastic scint. container • PMT coverage (12%) • PMT efficiency (20% @ 400 nm) • Eff. to detect/lose 1, 2 photons • Fiducial volume of VLAND vs interaction length of photons in oil • Rad length of oPs decay photons ~ 15 cm • ~50 cm between TPC & PMT faces • Need 4-6 rad length to guarantee photons interact (p.e., Compton) = Cerenkov radiation use pPs as calibration source H. Ray (P-25) Wednesday Seminar

  41. Fake Missing Energy • Fake occurs when : • coincidence in trigger • TPC identifies good e+ exiting away from endcaps • Good : proper E + momentum for Na decay, traveling from Na into aerogel, not exiting TPC in endcap region • Observe no photons in scint. container AND no photons in tank (aside from 1.275 MeV from Na) • Possibilities : • e+ absorbed in TPC outer shell  still forms Ps! • photons from Ps decay absorbed in aerogel/TPC shell/TPC endcap/Na source H. Ray (P-25) Wednesday Seminar

  42. Considerations • Stuff we’ve already considered … • Fake rate from trigger PMTs (Prob = 0.002) • Neutrino interactions from source in tank (0) • Effect of e+ irradiation of aerogel (0) • Effect of B field on aerogel (0) • Photon interactions in mineral oil • All e- from pPs p.e. effect will Cerenkov radiate • All pPs compton scattered e- will Cerenkov radiate • More complicated for oPs due to 3 photons (1 always causes Cereknov radiation), photon efficiency for detection .. • Calibration source (pPs) • Overlap of triggered evts w/ cosmics (0.3%) • Inner-brem of ele capture decays • Overlap of triggered evts w/ environmental radioactivity H. Ray (P-25) Wednesday Seminar

  43. Plans and Goals H. Ray (P-25) Wednesday Seminar

  44. Future Plans • Submit proposal for funding as LDRD/ER (Feb. 18th) (~145K-200K/year) • Use Directors Funds for TPC R&D (~20K) • working with Mike Ronan of LBL • C.D.R (Conceptual Design Report) published as pre-print • Attend TPC workshop at LBL in March • APS presentation in April (Tampa, FL) • 13th int. workshop on low E e+ and Ps physics in July (Campinas, Brazil) H. Ray (P-25) Wednesday Seminar

  45. Future Plans Pending LDRD/ER Funding • Prove that TPC technology works for oPs expt, allows greater sensitivities • Move to a larger tank (i.e. SNS!) • Place a new lower limit on the BR(oPs”nothing”) • (i.e. rule out a portion of extra-d theories) • Discover extra-dimensions! OR H. Ray (P-25) Wednesday Seminar

  46. Conclusions Why you should support LDRD/ER funding of VLADD • Demonstrate TPC oPs expts work  open up whole new world of sensitivity! • Can make definitive statement about R-S extra-d model (in final expt) • Bring GEM technology to LANL H. Ray (P-25) Wednesday Seminar

  47. Backup Slides H. Ray (P-25) Wednesday Seminar

  48. Current Assumptions • SM cannot propagate a large distance in extra-d without conflict with observations • Additional dim are acceptable if compact + sufficiently small to be consistent with current grav. tests • if “n” extra compact dim, Planck scale is related to the higher dim scale of gravity, M, through the relation M2Pl = M2+nVn, (V is the extra-d volume) H. Ray (P-25) Wednesday Seminar

  49. Current Assumptions • Can live in 4+n non-compact dim, in perfect compatibility with expt. gravity • Planck scale determined by higher-dim curvature, NOT by the size of the extra-d! • Assumptions rely on factorizable geometry (metric of 4-d is independ of coordinate in extra-d) Remove this assumption! H. Ray (P-25) Wednesday Seminar

  50. Types of Extra Dimensions (Particle Adventure) Compact, small extra dimensions (soda straw, rope) Branes -- extra dimensions are “out there” String is stuck to our brane, while gravity may propagate in all dimensions, or be confined to another brane. Space can be “warped”. There are lots of subtle variations of extra dimensions! (New York Times article) H. Ray (P-25) Wednesday Seminar

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