Display the Experiment Proposals for S1127

Experiment: S1127

Search for Exotic Particle Emission in the Decay of Trapped Isomers

by the TRINAT group

Data Analysis
Spokespersons:
J.A. Behr (TRIUMF)

Progress Report for EEC meeting 200907S

Table of Contents

Detailed Information

Complete/Merged PDF S1127_200907S_merged.pdf
Form data only S1127_200907S.pdf
Detailed Statement update09s1127e.pdf (477.06 kB)

Beam Shift Summary

12-hr ShiftsBeam Line / channelPriority
New Beam Requests
 6 TRINAT

June 2009 request: 2 for tuneup, 4 for counting. Tuning shifts can be shared with S1238

Committee Recommendations
 6 M

This experiment was first proposed in December, 2006 as a technique to either observe new massive particles or to set stringent limits on them. At that time, the Committee recommended that ‘the method should be better established before substantial effort and beam time is allocated to the effort. The best case system should be identified, presumably 81mRb, and the effort should be directed toward a demonstration of the technique and its potential.’ The progress report from the group described the work that has been done on 86mRb. The full complement of shifts was used to study the isomer decay in this nucleus. Several factors significantly reduced the sensitivity of this experiment. The analysis of the data indicates a loss of sensitivity, under the best conditions, to observe new particles from a projected 10-6 to about 2.5 x 10-4 branching ratio. This makes the technique somewhat less interesting as a way to constrain, or observe, new particles.

The Committee recognizes that a physics result from this work is needed to complete the Ph.D. thesis of a student who has developed this technique. An experiment to measure the 81mRb decay was proposed as a way to set limits on massive scalar particles and obtain this physics result. Little information was available to assess the importance of a limit on these particles at the level of a few 10-4. We urge the group to initiate contact with theorists to better understand this.

In view of the need to complete this project, we recommend that 6 shifts of 81mRb be allocated to obtain a publishable result for massive 0+ particles. Following the experiment, the group is urged to complete the analysis and submit the results for publication as soon as possible in order to assess the impact of the measurement and the importance of this class of experiments.

If in follow up analysis of the 86mRb data, the group finds more issues that impact the sensitivity limit for the measurement on 81mRb, they should consider using the six shifts to carry out a search for massive neutrinos as described in S1238.

Beam Shifts Used
 8 ISAC

Used on Schedule 116.

Beam Shifts Remaining
 0 -

As of December 3, 2009.


Membership

J.A. Behr TRIUMF Research Scientist 100 % Spokesperson
A. Gorelov TRIUMF PDF 100 %  
T. Kong University of British Columbia Student (PhD) 100 %  
M.R. Pearson TRIUMF Research Scientist 40 %  
K.P. Jackson TRIUMF Research Scientist 30 %  
D. Ashery Tel Aviv University Professor 20 %  
M. Dombsky TRIUMF Research Scientist 5 %  
P. Bricault TRIUMF Research Scientist 5 %  

Basic Information

Date Submitted
2009-06-07 20:31:15
Date Experiment Ready
2008-08-15
Summary *

June 2009: below is the previous summary. We will include the summary of the present update in the .pdf document. We will change isotopes. JB

Using TRIUMF's neutral atom trap (TRINAT), we are measuring the recoil
nucleus momentum in the decay of 86mRb.
The momentum will be smaller, Px = (Eγ2 - Mx2)1/2
if an unknown particle with mass Mx is emitted instead of a γ-ray. This general method searches for many possible particles that could be emitted in the decay of a nucleus. Our method does not rely on any information about interaction of the particles in any detector, or the lifetime of the particle, so our method has less model dependence than others.

This is what is called in high-energy physics a ``signature-based search''. There are perhaps a surprising number of physics motivations in this mass range, which we will discuss briefly.

We will mainly describe our experimental progress. The nuclear recoil in these cases is a neutral atom with kinetic energy < 1.9 eV. First we will describe our off-line progress: We have learned to efficiently photoionize these atoms as they leave the atom trap. We have shown that our configuration of electrostatic fields works and optimizes the momentum resolution. We have calibrated our new larger MCP and delay-line anode readout. (The detection methods and spectrometer methods are being considered for the 38mK beta-neutrino correlation upgrade.)

We will show the results from a test run at 1/500 the expected rate from
a poor tantalum target. We trapped 1000's of atoms of 86mRb and
found their optical isotope shift was in agreement with previous measurements.
We accomplished the most difficult task, finding the narrow two-photon resonance that we use as the first photoionization step, by trapping the 86gRb ground state. Then we measured in 90 minutes of counting a very small number of allowed gamma-ray recoils, within about 10% of possible rates.

So we have demonstrated all aspects of the experiment and now can complete it, once the beam is available in reasonable quantities. If 109/sec can be re-produced in the ion beam, we would be sensitive to rare branches of 10-6 per day of counting.

We request 10 shifts this time. The experiment is considerably more optically
complex than previous ones. Though almost all of the setup can be done on stable 85Rb (from a local source; ISAC not required), it is hard to guarantee success in less than this amount of time because of the several systems that must operate together.

This is the Ph.D. thesis of UBC student Tao Kong.

Plain Text Summary *
Using TRIUMF's neutral atom trap, we search for unknown massive particles that could be emitted in the gamma-decay of a nuclear isomer. We measure the momentum of the recoiling nucleus, which would be smaller if a massive particle were emitted than for the massless gamma ray. There are a surprising number of physics motivations for new particles with these masses.
Primary Beam Line
ISAC 2A
ISAC Facilities
ISAC Facility
TRINAT
Secondary Beam
Isotope(s)
81mRb
Energy
30
Energy Units
keV
Spot Size (mm, FWHM)
LEBT is fine(mm, FWHM)
Intensity Requested (pps)
2x10**10/sec from Nb or ZrC(pps)
Minimum Intensity (pps)
1x10**10/sec(pps)
Maximum Intensity (pps)
5x10**10/sec(pps)
Beam Purity (%)
Does not matter(%)
Experiment Support
Beam Diagnostics Required

Trap is powerful diagnostic. Local NaI detectors also.

Signals for Beam Tuning

Tuned Faraday cup on stable Rb, and ground state of 86gRb-- which is 10x the isomer-- was seen this way even with 1/500 production. TRINAT acceptance is 10x source emittance and 2x LEBT transmittance, so tuning is very simple.

DAQ Support
(Summary of Requirements)

Continued support of midtis01/CAMAC/VME for TRINAT. We have upgraded histrogramming to rootana-based system. We are implementing VME V1729 digitizer for delay-line anode readout

TRIUMF Support (Resources Needed)

Continued support of existing TRINAT lab at ISAC

NSERC

TRINAT project grant through April 2009; applied for 3-year grant

Other Funding
Safety Issues

Safety approval was granted for a run that was planned for full yields. (The 86gRb has an 18-day half-life and a 10% 1 MeV gamma along with 2 511's. Fields are projected to be 1 microS/hr 1 meter from the collection chamber after the run. Less than 1 ALI is produced, so normal TRIUMF procedures would be followed for any opening.) Laser safety is established inside the TRINAT room (the 10 Watt fiber laser is new, and the invisible light implies goggles for all personnel.)

Proposals and Progress Reports

200907S
200812S
200612S (Original Proposal)