Waveform Analysis for a Precision Pion Decay Measurementpen.phys.virginia.edu/talks/oakland_ap.pdf · Mean 314.6 ± 0.0 Sigma 0.4904 ± 0.0073 (ns) hodoscope e+ position - t 310 312

Waveform Analysis for a Precision Pion DecayMeasurement

Anthony Palladinofor the PEN Collaboration

University of Virginia

APS DNP Meeting; Oakland, California25 October 2008

Anthony Palladino (UVa) Waveform Analysis for a Precision Pion Decay Measurement 25 Oct ’08 1 / 23

Outline

IntroductionOverview of the PEN ExperimentConstraints on pseudoscalar and scalar couplings

PEN ExperimentDetectorExtracting the π+ → e+νµ Tail

Waveform DigitizerDigitizerWaveform Analysis

Conclusion


Introduction Overview of the PEN Experiment

Physics Motivation / Theory

• Precision Measurement of the π+ → e+ν branching ratio.

B =Γ(π+→e+νµ(γ))Γ(π+→µ+νµ(γ)) =

(ge

gµ

)2 (memµ

)2 (1−m2e/m2

µ)2

(1−m2µ/m2

π)2 (1 + δR)

Bcalc = (1.2352± 0.0001)× 10−4Cirigliano&Rosel, HepPH/07073439v1 (2007)

Bexp = (1.230± 0.004)× 10−4Experiment World Average (Current PDG)

Lepton Universality: W. Loinaz, et. al., Phys. Rev. D 65, 113004 (2004) [hep-ph/0403306](ge

gµ

)π

= 1.0021± 0.0016

Our Goal:∆Bexp

Bexp≤ 5× 10−4


Introduction Constraints on pseudoscalar and scalar couplings

Mass Limits on Leptoquark and Supersymmetric Particles

We will be able to give lower bounds on the masses of some hypotheticalparticles.

Mass of the Charged Higgs Boson: mH > 6.9 TeVMass of the Pseudoscalar Leptoquark: mp > 3.8 TeVMass of the Vector Leptoquark: MG > 630 TeV

Current limits: mH > 2 TeV, mp > 1.3 TeV, MG > 220 TeV.


PEN Experiment Detector

Beamline



20 cm

15 cm

75 cm 100 cm

45 cm

37.5 cm

21 cm

70 cm

276 cm

0.5 cm

32 cm~16 cm ~13 cm

PEN Experiment Beamline (Pase II : 2008)Not drawn to scale.

WallLead

O − Ring : 0.6 cm (un−compressed)O − Ring : 0.5 cm (compressed)

4.5 cm

B0

31.5 cm

8.9 cm

10.1 cm

14.2 cm

Thermal HouseWall

Frame

Figure: Beam Counter and Focusing Magnets.



Detector



Detector


PEN Experiment Extracting the π+ → e+νµ Tail

Tails via Geant4

Positron Energy in CsI (MeV)

Arb

itrar

y N

orm

aliz

atio

n

10-6

10-5

10-4

10-3

10-2

10 20 30 40 50 60 70 80 90 100

Must accurately distinguish the π+ → e+νµ events from the π → µ → eevents.

Suppress the Michel events and recover the π+ → e+νµ tail.


Waveform Digitizer Digitizer

Acqiris High Speed 10-bit PXI/CompactPCI Digitizer, Model DC2824 Channels, each with 2 GS/s

Digitized PMT waveforms from three beamline detectors:

• Beam Counter

• Degrader (wedge: left,right,top,bottom)

• Target



0 10 20 30 40 50 60 70 800

5000

10000

15000

20000

25000

30000

35000

40000

Degrader (Top) pion Waveform

0 10 20 30 40 50 60 70 800

5000

10000

15000

20000

25000

Target pion Waveform

Figure: System Response Functions (Waveforms).



Channel Number (ns*2)0 100 200 300 400 500 600 700 800

Tar

get D

SC A

mpl

itude

0

10000

20000

30000

40000

50000

60000

B0 Waveform


Tar

get D

SC A

mpl

itude

0

10000

20000

30000

40000

50000

60000

DEG LR Waveform


Tar

get D

SC A

mpl

itude

0

10000

20000

30000

40000

50000

60000

DEG TB Waveform


Tar

get D

SC A

mpl

itude

0

10000

20000

30000

40000

50000

60000

TGT Waveform

Figure: Digitizer Waveforms and Deconvolution Output.




Dig

itize

r A

mpl

itude

10000

20000

30000

40000

50000

60000

B0 Waveform


Dig

itize

r A

mpl

itude

20000

25000

30000

35000

40000

45000

50000

55000

60000

65000

DEG LR Waveform


Dig

itize

r A

mpl

itude

20000

25000

30000

35000

40000

45000

50000

55000

60000

65000

DEG TB Waveform


Dig

itize

r A

mpl

itude

20000

25000

30000

35000

40000

45000

50000

55000

60000

65000

TGT Waveform

Figure: Fitted Digitizer Waveforms.




Dig

itize

r A

mpl

itude

0

5000

10000

15000

20000

25000

30000

35000

TGT Waveform


Dig

itize

r A

mpl

itude

0

5000

10000

15000

20000

25000

30000

35000

TGT Waveform

Figure: Michel vs. π+ → e+νµ Waveforms.


Waveform Digitizer Waveform Analysis

Target Waveform Fit Parameters

Pulse Position in time (bin) Amplitude

π+ Known (from Degrader) Known (from TOF and EB0 +∑

Edeg )

µ+ Unknown Known

e+ Known (from Plastic Hod.) Known (from tracking)



π+ PositionDetermined from bin position of π in degrader.σ ∼ 110 ps

Entries 6505

Mean 33.26

Constant 13.5± 871.4

Mean 0.00± 33.25 Sigma 0.002± 0.224

mean in degraderπ mean in tgt - π31.5 32 32.5 33 33.5 34 34.5 35

0

100

200

300

400

500

600

700

800

900Entries 6505

Mean 33.26


Mean 0.00± 33.25 Sigma 0.002± 0.224

Figure: π+ Bin Prediction Accuracy



π+ Amplitude

Determined from TOF and the energy deposited in beam counter anddegrader.σ ∼ 250 keVee

deg + EB0 E

1600 1800 2000 2200 2400 2600 2800

310×

targ

et

E

500

600

700

800

900

1000

1100

310×Entries 6505

Mean 2.971e+06


Mean 1054± 2.964e+06

Sigma 886± 7.932e+04

target + Edeg + EB0 E

2000 2200 2400 2600 2800 3000 3200 3400 3600 3800

310×0

100

200

300

400

500

600

Entries 6505

Mean 2.971e+06


Mean 1054± 2.964e+06

Sigma 886± 7.932e+04

Figure: π+ Energy Prediction Accuracy, σ/mean = 2.6%



e+ PositionDetermined from the time of the Plastic Hodoscope.σ ∼ 250 ps

position in waveform (ns)+e300 305 310 315 320 325

(ns

)ho

dosc

ope

t

-10

-5

0

5

10

Mean 314.6


Mean 0.0± 314.6

Sigma 0.0073± 0.4904

(ns)hodoscope

position - t+e310 312 314 316 318 320

0

20

40

60

80

100

120

140

160

180

200

220 Mean 314.6


Mean 0.0± 314.6

Sigma 0.0073± 0.4904

Figure: e+ Timing Prediction Accuracy



e+ Amplitude

Determined from the distance e+ travels in the target.

Requires knowledge of the positron decay vertex.

• π+ entry position from wedged degraders.

• e+ track from MWPC, Plastic Hodoscope, and CsI Calorimeter.



µ+ Amplitude

Known precisely since it is a two body decay.σ ∼ 100 keVee

Entries 8924


Mean 89± 1.779e+05

Sigma 80.5± 7317

muE165 170 175 180 185 190

310×20

40

60

80

100

120

140

160

180

200 Entries 8924


Mean 89± 1.779e+05

Sigma 80.5± 7317

Figure: µ+ Energy from Waveform, σ/mean = 4.2%


Conclusion

Conclusion - PRELIMINARY

∆t = tµ - tπ (ns)

Eff

icie

ncy

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 10 20 30 40 50 60

(ns)π - t_µt = t_∆0 10 20 30 40 50

Eff

icie

ncy

0

0.5

1

1.5

2

• Currently, only the positions are implemented as initial fit parameters.This results in a reliable π → µ → e event identification with aπ+,µ+ separation as small as ∼ 1 ns.

• Inclusion of π+ and e+ amplitude data will increase speed andaccuracy.


Conclusion

PEN Experiment collaboration members:

L.P. Alonzi,a V. A. Baranov,c W. Bertl,b M. Bychkov,a Yu.M. Bystritsky,c

E. Frlez,a V. Kalinnikov,c N.V. Khomutov,c A.S. Korenchenko,c

S.M. Korenchenko,c M. Korolija,f T. Kozlowski,d N.P. Kravchuk,c

N.A. Kuchinsky,c D. Mekterovic,f D. Mzhavia,c,e A. Palladino,a,b

D. Pocanic,a P. Robmann,g O.A. Rondon-Aramayo,a

A.M. Rozhdestvensky,c T. Sakhelashvili,b V.V. Sidorkin,c U. Straumann,g

I. Supek,f Z. Tsamalaidze,e A. van der Schaaf,g E.P. Velicheva,c

V.V. Volnykh,c

aDept of Physics, Univ of Virginia, Charlottesville, VA 22904-4714, USAbPaul Scherrer Institut, CH-5232 Villigen PSI, SwitzerlandcJoint Institute for Nuclear Research, RU-141980 Dubna, RussiadInstitute for Nuclear Studies, PL-05-400 Swierk, PolandeIHEP, Tbilisi, State University, GUS-380086 Tbilisi, GeorgiafRudjer Boskovic Institute, HR-10000 Zagreb, CroatiagPhysik Institut der Universitat Zurich, CH-8057 Zurich, Switzerland


Conclusion

Paul Scherrer Institute


Waveform Analysis for a Precision Pion Decay Measurementpen.phys.virginia.edu/talks/oakland_ap.pdf · Mean 314.6 ± 0.0 Sigma 0.4904 ± 0.0073 (ns) hodoscope e+ position - t 310 312

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