(tau neutrino magnetic moment)

Reinhard Schwienhorst

University of Minnesota

Donut analysis

Talk at Nagoya University, 6/9/99

Outline• Introduction

• Physics– magnetic moment interaction– Expected event yield

• Spectrometer analysis:– Monte Carlo Analysis– Cuts

• Preliminary Physics result

• Conclusions

All of the numbers in this presentation are preliminary

Introduction• Standard Model

– =0

• current experimental limit: – e:<1.810-10B

– :<7.410-10B

– :<5.410-7B

(all obtained in neutrino-electron scattering experiments)

Magnetic moment interaction

e

e

Magnetic moment interaction example (MC)Title:event.ps (Landscape A 4)Creator:HIGZ Version 1.25/05Preview:This EPS picture was not savedwith a preview included in it.Comment:This EPS picture will print to aPostScript printer, but not toother types of printers.

Magnetic moment interaction example (MC)Title:event.ps (Landscape A 4)Creator:HIGZ Version 1.25/05Preview:This EPS picture was not savedwith a preview included in it.Comment:This EPS picture will print to aPostScript printer, but not toother types of printers.

Title:event.ps (Landscape A 4)Creator:HIGZ Version 1.25/05Preview:This EPS picture was not savedwith a preview included in it.Comment:This EPS picture will print to aPostScript printer, but not toother types of printers.

Physics reminder

• Neutrino-electron scattering– no hadronic activity in the event– small forward angle

• magnetic moment interaction– cross section

÷øö

çèæ -µ 12

T

E

dT

d s

• : neutrino magnetic moment• E: neutrino energy• T: electron kinetic energy

Electron energy and angleTitle:pawprint.epsCreator:HIGZ Version 1.23/09Preview:This EPS picture was not savedwith a preview included in it.Comment:This EPS picture will print to aPostScript printer, but not toother types of printers.

Title:pawprint.epsCreator:HIGZ Version 1.23/09Preview:This EPS picture was not savedwith a preview included in it.Comment:This EPS picture will print to aPostScript printer, but not toother types of printers.

Production angle and energy for the electron in a magnetic moment interaction

Expected event yield• If =5.410-7B (the current limit):

– with an electron energy cutoff at 5GeV• current cat3 neutrino event sample

• expect 10 magnetic moment interactions

• (compared to 40 CC interaction)

– with an electron energy cutoff at 0.5GeV• .nustrip files

• expect 30 magnetic moment interactions

– with an electron energy cutoff at 10MeV• emulsion analysis

• expect 80 magnetic moment interactions

• we must scan at least 1/3 of the emulsion to improve the sensitivity

Emulsion-only analysis• Scan a large volume of the emulsion

• Search for single electron tracks in the direction of the beam – challenges:

• identify electrons down to very low energies

• many straight tracks in the emulsion

• Advantage: independent of the spectrometer, time, trigger

• disadvantages: – must scan a large volume– background from pair production

Spectrometer analysis outline• Optimize cuts for magnetic moment events

– cross-check with CC events (data and MC)

• easy to find

determine efficiency

• apply to neutrino candidate events– apply first to MC events, determine expected # of events

– blind analysis

• apply to nustrip files– find (almost) all candidate events

– not quite a blind analysis

• at the end, scan emulsion for confirmation– identify hadrons, decays, secondary interactions, nuclear

breakup

Monte Carlo analysis

• So far only periods 3 and 4

• Trigger efficiency =65% for magnetic moment interactions with T>0.5GeV

• Tune each cut to remove no more than ~5% of the magnetic moment interactions

Cuts• Muon ID

– remove muons and hadrons

– watch out for noise require <2 MID hits (sum over all tracks)

• EMCAL– require EEMCAL<20GeV

– require for each track with P>4GeV that EEMCAL<P/2 for blocks within 0.2m of the track

– check the rectangle with |x-xvtx|<0.7m and |y-yvtx|<0.2m :• require at least 50% of the EMCAL energy to be inside the rectangle

• require the energy outside the rectangle to be less than 1GeV

Cuts II• SF system:

– require small # of SF hits (< 12000)

– remove events with:• hadrons: highly ionizing tracks (large fiber pulseheight)

• tracks not coming from the emulsion (muons interacting in the shielding)

• tracks that go straight through a module (electrons are required to shower)

– require at least one straight SF line in each view (<0.1rad)• put the vertex at the origin of this line

– require the vertex to be in the emulsion volume

Cuts III• Trigger counters:

– remove backward trigger O O O O O O O O T1O O X X O O O O O T2 O O X O O O O O T3

– require a trigger panel hit on a straight line behind the vertex

• VDC:– require VDC hits on a straight line behind the vertex

Cut efficiency:electronic analysis

Percentage ofevents removed in periods 3+4

Data:cat 3

Data:nustrip

MC: CC

MC:e CC

MC:NC

MC:magmom

Begin # of events 700 120000Muon ID cut 60% 10% 86% 48% 52% 8.3%First EMCAL cut 23% 18% 16% 52% 12% 6.4%Hadrons in SF, olddecoder

35% 26% 23% 39% 28% 0.9%

SF lines not fromemulsion

65% 79% 6.4% 21% 3.6% 8.2%

Long SF lines 20% 22% 41% 41% 21% 3.3%

Remaining # ofevents

38 (5%) 20000(17%)

(5%) (7%) (23%) (75%)

# of SF hits 0% 0.1% 0% 0% 0% 0%Hadrons in SF, newdecoder

20% 1.1% 6.6% 21% 6.7% 2.8%

Straight SF line Not used 95.4% 42% 29% 15% 31.1%Vtx in emulsion 13% 24% 4% 4.7% 5.2% 3.8%Backwards trigger Not used 23% 8.2% 14.1% 15.1% 11.7%Trigger counterbehind vertex

4% 40% 3.4% 0% 0% 0%

VDC hits behindvertex

33% 45% 10.5% 2.4% 2.7% 2.4%

vertex in EMCAL 50% 75% 50% 85% 6% 11.8%

Resulting # ofevents

5(0.7%)

81(0.07% )

(1%)(1.8%forcat3)

(0.5%)(0.8%forcat3)

(7.8%)(10.8%forcat3)

(37%)(61%forcat3)

Cuts IV• Refit and find the vertex

• remove events “by hand” if:– a straight muon is in the SF– the event has only a single track with P>0– there are slow hadrons in the SF

• apply all of the previous cuts again

• output: 3 cat3 events, 14 nustrip events– periods 3 and 4– MC efficiency for these cuts 100%

Cuts V

• Careful visual inspection of each event– Can it be scanned?

– Check EEMCAL/P for each track

– Check track straightness (angle <0.1rad in X and Y)– check trigger timing

• Output: 0 cat3 events, 1 nustrip event– if current limit: expect 6 cat3 events, 11 nustrip

events

Candidate eventTitle:event.ps (Landscape A 4)Creator:HIGZ Version 1.25/05Preview:This EPS picture was not savedwith a preview included in it.Comment:This EPS picture will print to aPostScript printer, but not toother types of printers.

Candidate eventTitle:event.ps (Landscape A 4)Creator:HIGZ Version 1.25/05Preview:This EPS picture was not savedwith a preview included in it.Comment:This EPS picture will print to aPostScript printer, but not toother types of printers.

Title:event.ps (Landscape A 4)Creator:HIGZ Version 1.25/05Preview:This EPS picture was not savedwith a preview included in it.Comment:This EPS picture will print to aPostScript printer, but not toother types of printers.

Preliminary Physics result

• Data analysis:– 0 events for T>5GeV– 1 events for T>0.5GeV– systematic error: not determined yet, assume

0.5events

• preliminary 90% confidence limit for the magnetic moment:

B

7103 -´<

Conclusions

• The magnetic moment analysis is still in progress

• Searching for event candidates in the nustrip files will give the best limit

• Emulsion information for candidate events is very important

• An emulsion-only analysis is only useful if we scan a considerable fraction of the emulsion volume