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Window of Opportunity. … Physics . There are mysteries in the neutrino mass spectrum which a complementary, direct measurement can help unravel. Oscillation Exp. only sensitive to D m 2 n disappearance => oscillation => mass 2-flavor mixing is much easier to write down

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slide1

Window of Opportunity

… Physics ...

There are mysteries in the neutrino mass spectrum which a complementary, direct measurement can help unravel.

Oscillation Exp. only sensitive to Dm2n disappearance => oscillation => mass 2-flavor mixing is much easier to write down

Astrophysics/Cosmologyno sterile n, standard model interactions, stable n

Supernovaeonly applies to Dirac neutrinos model-dependent at supernuclear densities

… Experiment …

G-2 storage ring: state-of-the-art spectrometer at bargain prices

Beamlinecan be parasitic with SEB, easily switched to RHIC, FEB

An order of magnitude improvement in a fundamental constant

slide2

A stricter limit is part of this decade’s focus on neutrino physics

PRESENT

Atmospheric: nm=> nXand Dm2 ~.0012 - .008 eV2 (SuperK: nm=> nt slightly favored)

Solar Neutrino: ne => nX and Dm2 ~ 10-6eV2 or is it 10-11 eV2 ? (SNO may help)

LSND nm => ne and Dm2 ~ .03-1.0 eV2

FUTURE

MINOS - Beams early 2004 CERN - Beams early 2005

K2K - 220 evts by 2005 (if Dm2 large)

MiniBoone in 2003, Boone in ??

The next Supernova - Tools to interpret and limit

slide3

Closing Loopholes

Neutrino decay

nm -> ne ne ne via DLo (minimal LR symmetric model) consistent with

Mass Density of UniversePrimordial nucleosynthesis Microwave Bkgd Diffuse g-ray Bkgd SN1987a

as long as m(nm) > 35 keV (from Z-width)

Supernovae

For m(nX)> 10 keV, Dt ~ day => pulse is below background if SNO sees no delayed pulse, then take your pick:No nX produced? Oscillated to n(sterile)? They decayed? nm is massive?

Check out all those 17 keV papers for more exotic loopholes

slide4

dGF dtm 5dmm 4m2

GF 2tm 2mmm2m

nm

0.5 ppmMuLan

10 ppm

0.38 ppm

It is, after all, a Fundamental Constant !

Its uncertainty affects our knowledge of other fundamental constants

For example:

* Mass of the pion as measured by decay of stopped p’s

* Gfermi theoretical precision negligible compared to experimental variables other electroweak variables, such as MZ, continue to improve

slide5

Direct Measurements are …more direct!

Current Limits

m(ne)< 4.35 - 15 eV Tritium b-decay endpoint < 23 eV TOF spread from SN1987A< 0.5 - 9 eV Double b-decay for Majorana n’s

m(nm) < 170 keV p -> mn (stopping p’s)

m(nt) < 18.2 MeV Inv. Mass of t -> n + hadrons (e+e- Colliders)

slide6

DIRECT MEASUREMENTS OF M(nm)

Pure 2-body decay p -> m n No model-dependent nuclear/atomic environment

Pions live a reasonably long time

Pion Decay at RestParent pmomentum is well-known Limited by the uncertainty in the pion mass

Pion Decay in Flight Need to measure pp-pm Momentum Resolution limited by mult.scattering in detectors

slide7

Pion Decay at Rest

Series of experiments at PSI

1979:Daum et al. (Phys Rev D20 p.2692) Solution A Solution B

1984:Abela et al (Phys Lett B146 p.431) Solution A Solution B

1996:Assamagan et al. (Phys RevD53 p.6065) Solution A Solution B

m2(nm) = + 0.13 +- 0.14 - (MeV/c2)2

m(nm) < 570 keV/c2

m2(nm) = - 0.163 +- 0.080 - (MeV/c2)2

m(nm) < 250 keV/c2

m2(nm) = - 0.143 +- 0.024 -0.016 +- 0.023 (MeV/c2)2

m(nm) < 170 keV/c2

slide8

Pion Decay in Flight

1982:Anderhub et al. Phys Lett B114 p.76

m2(nm) = - 0.14 +- 0.20 (MeV/c2)2

m(nm) < 500 keV/c2

2002:BNL g-2 Neutrino Mass Experiment?

m(nm) < 8 keV/c2

If SuperK definitively proves nm=> nt (Dm2~.007) Then this experiment reduces the t neutrino mass limit by 3 orders of magnitude!

slide9

Highlights of the Experimental Technique

  • Translate Dp to Dr in 0.1 ppm uniform B-Fieldno multiple scattering no need to measure decay angle or location
  • Reference each m to parent pslow extraction
  • In situ alignmentprotons (7 ns/turn late) prescaled undecayed pions remote positioning of active vetoes remote angular adjustment of detector
  • Position resolution from silicon1.4 mm SSD
  • Time resolution from scintillators and PMT’stight triple coincidence trigger TDC’s on all vetoes and embedded hodoscope
slide10

In a perfectly uniform B-fieldAny charged particle returns to origin independent of B, p, q

* Origin can produce a range of angles and momenta * Uniformity is more important than value of B* 1st harmonic (and other nonuniformities) are always monitored using residuals of prescaled pions and undecayed protons

“origin”

slide11

G-2 Storage Ring

G-2 Experiment Weak-focussing Storage Ring: Muons stored for 800 ms Quadrupoles Muon Kicker

NuMass Experiment Spectrometer: p -> mn observed evt-by-evt No Quads Pion kicker

Same Momentum - 3 GeV retain excellent shimming and B-field uniformity 0.1 ppm over 4.5 cm Trolley runs in vacuum to map field Fixed probes to track changes Active shimming and thermal insulation to minimize change

slide12

Put pions on orbit using dE/dx Injection 5.2 cm Beryllium

p orbit withoutdegrader

p orbit with degrader

“Pion Kicker”

D p = -16.2 MeV/c X/Xo = 14.7 %q (rms) = 1.56 mr

slide13

Conceptual Design

Forward-going decay muons orbit a larger diameter byDD

CM

nm p m

q = 29.7 MeV/c

undecayed pions

D

DD pm - pp 0.7 MeV/c 3.26 mmD pp3 GeV/c 14 m

DD

decay m’s

dD depends on m(n)

non-zero mn shrinks DD

dD -mn2 D 2 q mp

0.04 mm for current limit

slide14

DD pm - pp 0.7 MeV/c 3.26 mmD pp3 GeV/c 14 m

Conceptual Design

Forward-going decay muons orbit a larger diameter byDD

CM

nm p m

q = 29.7 MeV/c

undecayed pions

D

DD

decay m’s

slide15

dD depends on m(n)

non-zero mn shrinks DD

dD -mn2 D 2 q mp

0.04 mm for current limit

slide16

J-Veto

Non-forward going muons are lower momentum

They move to the inside of S2

Also vetoed offline by the g-2 calorimeters and J veto

g-2 Cal’s

S1

S2

slide17

Experimental Method

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

S1

S2

Trigger Hodoscope

slide18

Silicon mstrip Detectors (S1, S2)(1.28 cm long vertical strips at 50 mm pitch)

S2

Embedded Scintillator:2 mm Prescale Strips Trigger pads

S1

6.4 cm

BerylliumDegrader

2.56 cm

slide20

Sample & Hold Readout System

Simple Standard Cheap

225 ns

Beam Counter

150 ns

Hodoscope

Trigger:latch data

p

1st turn:

S1 (ch 6)

O

m

2nd turn:

S1 (ch 71)

O

1st turn:

S2 (ch 6)

p

O

m

S2 (ch 71)

2nd turn:

O

slide21

Running Time

5% of SEB beam => 492 hrs (crystal extr. eff.)

Parasitic Running

E952 Parameters2.8 x 106p+into g-2 ring/TP5.4 x 1012p+for an 8 keV result

E949 Running Conditions

25 Gev protons70 TP in a 4.1 s spill / 6.4 s cycle

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

slide22

Scintillator Hodoscope

Radial segmentation = 2 mm Vertical segmentation = 12.8 mm

  • 4 ns gate for 3-fold coincidence triggerAccidentals at 0.004, flagged by beam counter
  • Veto events Dr < 2mm to enrich p-m eventsx 50 prescale => 0.5 MB/s or 37 DLT tapes
  • Select readout SSD0.7% dead time 1/10 data volume
  • 1 ns timing resolution (TDC) + 2mm segmentationreject accidentals offline (another factor of .002)
slide23

Sources of Background

  • Beam-gas scattersvacuum is 10-6 torr
  • Injected p (27%)7 ns/turn slower
  • Injected e (12%)lose 1 MeV/turn from SR (4.7 mm inward) identify in J-Veto calorimeter (or position)
  • m => enn(gt = 64 ms)injected m (1%) and p =>mn < 10 -4 of good p -m events rejected by g-2 calorimeters
  • p => en (BR=1.2 x 10-4)low tail out to ~ 5 mm calorimeter at inner J-Veto
slide24

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

slide25

Schedule

Summer 2000 Test individual SSD’s at CERN

Spring 2001 Do tests at end of g-2 run (fast extraction)

Insert 2 SSD’s in rigid frame with removable “degrader” p-inj, low intensity, no quads, no kicker No degrader: m-m, p-J-veto Degrader: m- J-veto, p-p

Summer 2001Test of crystal extraction for Slow Beam

2001 Build mosaic of SSD Customize VA readout (chip run) Tests of detector at CERN test beam

2002 Engineering run - parasitic with E949 Crystal extraction: slow beam down V-line Final 5x5 SSD configuration with degrader in ring

2002 Physics run - parasitic or dedicated

slide26

Responsibilities

Beamline and Ring BNL

SSD and readout electronics CERN, Minnesota

Active Vetoes and Scint Trigger BU, Illinois, Tokyo IT ??

Feedthrus and positioners Tokyo IT, Heidelberg ??, BNL

DAQ and g-2 electronics Existing (Minnesota, BU)

Field Measurements Yale, Heidelberg, BNL

Orbital dynamics, Monte Carlo Cornell, BNL, Yale, NYU, Minn, BU

Analysis The team!

slide27

Goals of the 2001 Test Run

  • Check out trigger and DAQ modifications
  • Read out silicon microstrip prototype detector in g-2 conditions
  • Beamline settings for pion injection link to position of pion and muon at detector and J-veto most efficient angle thru inflector
  • Map scattering background in g-2 Cal, FSD, J-Veto
  • Practice tightening profile using beamline
  • Practice tightening profile using current shims
slide28

Problems: Fast extraction, high intensity, msec shaping timeConditions: No vacuum, no kicker, no quads, reverse B-field

  • Inject positive pions at 0.5% above magic momentum
  • Observe trigger hodoscope(TDC and ADC gives 2 rough profiles 150 ns apart)
  • No degraderFind 1st pass pion distribution and 2nd pass muon distribution Some storage: tune on fast rotation in detectors Check lifetimes of lost muons vs positrons in FSD’s See pions at Flash Counter on 1st turn
  • DegraderFind 1st pass pion and 2nd pass pion distribution No storage: Check lifetime of lost muon distribution No pions on Flash Counter Muons scraped off inner J-Veto after 1st pass and pions after 2nd
  • Read out microstrip detector as well, but unable to do residuals..yet
  • Gradually reduce emittance and then reduce intensity How low a rate can we get? Can we find the on-orbit protons 7 ns later?
  • Watch FSD, PSD and CAL detectors, collect information on the scattered background - electrons? muons?
  • Delay S2 microstrip trigger to remove 1st pass in S2
slide29

S1

12.8 mm

12.8 mm

Prototype SSD’s from CERN

g-2 Test setup

S2

PSD tiles

Trigger tiles

Removable Copper sheets

slide30

Using VA-2 chip: 800 ns shaping time

225 ns

Beam Counter

150 ns

Hodoscope

Trigger S2

Trigger S1

p

1st turn:

S1 (ch 6)

O

m

2nd turn:

S1 (ch 71)

O

1st turn:

S2 (ch 6)

p

O

m

S2 (ch 71)

2nd turn:

O

More Accidentals and More Deadtime

slide31

T0

J-Veto

Inflector

Flash Counter

Pion hits inflector

Muon on orbit

collimator

No Degrader

pion => muon residual profile

slide32

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