VLADD

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VLADD

• VLAnd extra Dimensions Detector
• H. Ray, R. V. de Water (LANL)
• P. Vetter (LBL)
• (LANL G. Garvey, B. Louis, G. Mills)

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Documentation
http//home.fnal.gov/hray

• TDR (extensive calculations included)
• References from TDR
• LDRD/ER proposal
• All talks VLADD related

work in progress
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Outline

• Intro to Positronium
• Theoretical Motivation
• VLADD Detector Design
• Event Selection
• Some Numbers
• Future Plans

See P. Vetters Jan. 25th LANL talk on web
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Positronium
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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 (0,0gt)
• ? 0.125 ns
• Spin 1 (3S1) orthopositronium (oPs), triplet
  state (1,1gt, 1,0gt, 1,-1gt)
• ? 142.074 ns (vacuum)

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Decay of States

• SM couplings to ?, ?-? pair
• pPs ? ?-? pair suppressed by (m?/me)2
• oPs ? ?-? pair G2F?3m5e / 24?21?4sin2?w2
• 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 2S1Ljgt -1LS 2S1Ljgt
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oPs Energy Spectrum
1.5
1.4
0.8
0.4
Ps total E 1.022 MeV
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Why Search for Invisible oPs Decays?
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Review R-S Extra-D
hep-th/9905221 RS hep-th/9906064 RS

• 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
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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

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oPs?Nothing Rate
Ps has no quantum s, longest lived ferm-antiferm
bound state
Br(oPs?nothing) 3104 (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
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A search for (o-Ps -gt 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.

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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

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Previous oPs-gt Nothing Experiments
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Previous Searches (?)

• 1989 Atoyan, Gninenko, Razin, Ryabov
• BR lt 5.8 x 10-4 (90 CL)
• 1993 Mitsui, Fujimoto, Asai, et. Al.
• BR lt 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 .
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VLADD
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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
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Atoyan et al. 1989
10 -4
Excluded by BBN
10 -5
VLADD
Mitsui et al. 1993
10 -6
10 -7
ETH Zurich, proposed
Milicharged particles, Mirror matter
Branching ratio (o-Ps -gt invisible)
10 -8
LBNL/LLNL 1st design proposal
Limit from width of (Z0 -gt invisible)
10 -9
Allowed region for (o-Ps-gtg-gtextra dimensions)
final goal
10 -10
Triviality extra dimension physics happens at gt
10 TeV
Neutrino magnetic moment
(o-Ps -gt nn)
10 -18
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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)

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Overview
PMTs
e
Cerenkov cones
e-
Sodium-22
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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

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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 _at_ 408 nm
• lt 100 keV X-rays
• Alpha, beta particles

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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
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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 (801010) 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)
• RD 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 RD funds come in ..
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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
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GEM Technology
Total gain 102 (single) - 105 (triple)
www.lnf.infn.it/seminars/talks/murtas_28_11_02.pdf
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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 _at_ 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!
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SiO2 Aerogel

• Particles 2-5 nm diameter, pores 2 to gt 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 _at_ 800 C
• Doping possible

RD
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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 _at_ 425 nm

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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.
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VLAND Tank
Dude, where are the Extra-ds???
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B-Field

• 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?

Max separation

• _at_ TPC resolution of 200 ?m, resolve e, e- w/ KE
  8.1 MeV

?Sgt 1 0,0gt - 0.0002205 1,0gt ?Tgt 0.0002205
0,0gt 1 1,0gt
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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
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6 mm thick layer of SiO2 aerogel
Positron source (22Na)
Two scintillator layers, each read out by its own
PMT
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Scintillating plastic vessel
Positron source (22Na)
Two scintillator layers, each read out by its own
PMT
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2 m long
1 m radius
Typical PMTs
VLANDtank
13 cm long 13 cm high
VLADD
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The Numbers
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Event Selection

• 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

On-line
Off-line
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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

RD!
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Detection Efficiency

• photons absorbed/interact in plastic scint.
  container
• PMT coverage (12)
• PMT efficiency (20 _at_ 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
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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

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Considerations

• Stuff weve 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

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Plans and Goals
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Future Plans

• Submit proposal for funding as LDRD/ER (Feb.
  18th) (145K-200K/year)
• Use Directors Funds for TPC RD (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)

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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
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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

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Backup Slides
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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 M2nVn, (V is the extra-d
  volume)

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Current Assumptions

• Assumptions rely on factorizable geometry (metric
  of 4-d is independ of coordinate in extra-d)

• Can live in 4n non-compact dim, in perfect
  compatibility with expt. gravity
• Planck scale determined by higher-dim curvature,
  NOT by the size of the extra-d!

Remove this assumption!
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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)
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Extra Dimensions Theory
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R-S Model

• Real world described using warped geometry
• defines universe as 5-D anti-de Sitter space, two
  4-D branes
• all elementary particles (SM) except graviton
  localized on 31D brane
• Gravity confined to Planck scale physics brane
• Fermions obtain mass by interacting weakly
  across warped bulk

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R-S Model

• Brane world massive matter becomes unstable due
  to tunneling into additional 5th dimension
• (this feature is generic to fields with bulk
  modes)

Also generates a Kaluza-Klein tower of graviton
modes, and possibly other particles.
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Kaluza-Klein Modes are generated in X-Dim theories
If the extra dimension is compact, then momentum
is quantized along that dimension
P n R
This generates new particle modes at
different masses
R
Mn2 M02 n2 / R2
This is usually referred to as the Kaluza-Klein
tower of modes
Gravitons in all these models have KK-modes, and
in some models, other bosons (g, W, Z) do as
well These could in principle be detected at
collider experiments (TeV level) Unless the
number of XDs is big!
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Why Positronium?

• Pure QED state
• No net gauge quantum numbers
• No gauge symmetries to confine to our brane
• Long lifetime - longest lived fermion-antifermion
  bound state
• prob to osc. into extra-d scales with ratio of
  lifetime to complex phase (extra-d) of lifetime

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Lifetime vs Counting

• AFS Adkins, Fell, Sapirstein
• Pick-off rate estimates were the problem!

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Possible Failure Modes

• Vacuum broken
• TPC outer layer tears gas enters aerogel
• Acrylic container cracks oil enters aerogel

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