# Presentation: 544737

## 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

- 1/26/05

## 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

- 1/26/05

## 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

- 1/26/05

## Positronium

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## Positronium

- Bound state of an electron and positron
- no nuclear structure
- Bound + annihilates through EM interactions

- _[http://positrons.physics.lsa.umich.edu](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

- 1/26/05

## 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

- 1/26/05

## oPs Energy Spectrum

- Ps total E    ~1.022 MeV

- 1.5

- 1.4

- 0.8

- 0.4

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## Why Search for Invisible oPs Decays?

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## Review : R-S Extra-D

- 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

- Real world described using warped geometry
- defines universe as 5-D anti-de Sitter space, two 4-D branes

- hep-th/9905221 : R&S
- hep-th/9906064 : R&S

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

**Notes:**
Brane = 3 d surface

Higher-dimensional space = bulk mode

## 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

- 1/26/05

## oPs”Nothing” Rate

- Br(oPsnothing) ≈ 3·104 (moPs / k) 2

- 4 ·10-9  Br(oPs”nothing”)  O(10-10)

- Bound on k from LEP data on Z nothing : k 2 TeV
- Solve gauge hierarchy with extra infinite d, k ≤ O(10) TeV

- Dubovsky, Rubakov, Tinyakov, PRD **62**, 105011
- Gninenko, Krasnikov, Rubbia, PRD **67**, 075012

- Ps has no quantum #s, longest lived ferm-antiferm bound state

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## A search for (o-Ps -> “nothing”) at a level below 1e-10 is appealing

-  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.

- A search for (o-Ps -> “nothing”) at a level below 1e-10 is appealing

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## 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

- 1/26/05

## Previous oPs-> “Nothing” Experiments

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## 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

- 1/26/05

**Notes:**
1989 : sodium 22, gas proportional chamber for e+ detection, aerogel target, 
NaI calorimeter and counters for detection 1.275 MeV gamma with positron.  
1993 : sodium 22, plastic scintillator, aerogel, acrylic to stop any escaping positrons, 
Surrounded by NaI and CsI counters
2003 : e+ from pulsed beam are stopped in MgO target.  ExB filter to remove electrons 
Created by e+ hitting target, microchannel plate for tagger, BGO crystal calorimeter

## VLADD

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

##   VLADD is a counting experiment, not a lifetime measurement!

- Two ways to search for a new decay
-                 counting
-               lifetime

-   VLADD is not the final goal - this is a *demonstration* experiment

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## VLADD

- 10 -4

- 10 -5

- 10 -6

- 10 -7

- 10 -8

- 10 -9

- 10 -10

- 10 -18

- (o-Ps -> )

- Atoyan et al. 1989

- Mitsui et al. 1993

- Triviality:
- extra dimension physics
- happens at > 10 TeV

- Limit from width of (Z0 -> invisible)

- ETH Zurich, proposed

- LBNL/LLNL 1st design proposal

- Allowed region for (o-Ps->->extra dimensions)

- Branching ratio (o-Ps -> “invisible”)

- Excluded by BBN

- Milicharged particles,
- Mirror matter

- Neutrino
- magnetic moment

- final
- goal

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## 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

- 1/26/05

## Overview 

- e+

- e-

- PMTs

- Cerenkov
- cones

- Sodium-22

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## 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

- 1/26/05

## 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

- 1/26/05

## TPC

- HV central membrane

- Outer field cage

- Inner field cage

- Endcap - anode,
- traditionally wire
- chamber

- B

- E

- Gas filled chamber

- e+

-    e- created
- in gas

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## 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

- 1/26/05

## GEM Technology

- Cathode

- ~3 mm conversion and drift region

- 1 GEM

- ~1mm induction gap

- PCB w/ pick-up strips (anode)

- 2 sided Cu foil
- diameters 70 m

- pitch of 140 m
- ~100 m thick

- drifting ele guided into holes

- Pot. Diff (400-500V)
- between electrodes

**Amplification!!**
**each hole = indivdual prop. counter**

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## 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

- 1/26/05

## 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

- 1/26/05

## 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

- 1/26/05

## 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

- 1/26/05

## VLAND

- 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.

- Complete construction March/05

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## VLAND Tank

- Dude, where
- are the
- Extra-ds???

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## 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?

- |S> = 1 |0,0> - 0.0002205 |1,0>
- |T> = 0.0002205 |0,0> + 1 |1,0>

- @ TPC resolution of 200 m, resolve e+, e- w/ KE 8.1 MeV

- Max separation

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## 12 cm long

- 6 cm  outer
- radius

- 0.5 cm
- inner
- radius

- Two scintillator layers,
- each read out by its own PMT

- Positron source (22Na)

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## Two scintillator layers,

- each read out by its own PMT

- Positron source (22Na)

- ~6 mm thick layer of SiO2 aerogel

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## Two scintillator layers,

- each read out by its own PMT

- Positron source (22Na)

- Scintillating
- plastic
- vessel

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## 2 m long

- 1 m
- radius

- ~13 cm long
- ~13 cm high

- VLANDtank

- VLADD

- Typical PMTs

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

##  The Numbers

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## 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

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## 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

- 1/26/05

## 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

- 1/26/05

## 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

- 1/26/05

## 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

- 1/26/05

## Plans and Goals

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## 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

- 1/26/05

## 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

- 1/26/05

## Conclusions

- 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

- Why you should support LDRD/ER funding of VLADD

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## Backup Slides

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## 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

- 1/26/05

## 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!

- Remove
- this assumption!

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

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## Types of Extra Dimensions

- 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)

- (Particle Adventure)

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## Extra Dimensions Theory

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## 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 3+1D brane
- Gravity confined to Planck scale physics brane
- Fermions = obtain mass by interacting weakly across warped bulk

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

**Notes:**
Brane = 3 d surface

Higher-dimensional space = bulk mode

## 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.

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

**Notes:**
Brane = 3 d surface

Higher-dimensional space = bulk mode

## Kaluza-Klein Modes are generated in X-Dim theories

- If the extra dimension is compact, then momentum is quantized along that dimension:

- R

- P = n R

- This generates new particle modes at different
- masses

- 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 (, W, Z) do as well
- These could in principle be detected
- at collider experiments
- (TeV level)
- Unless the number of XD’s is big!

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## 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

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

**Notes:**
K = parameter determined by five-d planck mass and bulk cosmological constant.

Massive particles are strictly confined to our brane --  Gauge physics is geometric in our 4-D
    Gauge symmetries generate quantum numbers (lepton #, flavor, charge, baryon #, color)

From vetter : The lifetime business is crucial, though, as I understand it.
The existence of extra dimensions as a potential decay mode for
the Ps provides a complex part to the decay width of the state,
and the probability to go to extra dimensions scales with the ratio
of the ordinary lifetime to the complex phase argument, in much
the same way as the process of quantum tunneling through a barrier
works.

## Lifetime vs Counting

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

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

## Possible Failure Modes

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

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05

- H. Ray   (P-25)  Wednesday Seminar

- 1/26/05