inclusive measurement of br(d x) and the neutrino spectrum

Inclusive Measurement of BR(D X) and The Neutrino Spectrum

Michael Weinberger

CLEO-c

Cornell University

Lake Louise Winter Institute

February 22, 2004 Michael Weinberger Cornell University Lake Louise Winter

Institute

2/16

CLEO-c•CESR: symmetric e+e- accelerator•57.2 Pb-1 data at (3770) used for this analysis

•Charm production threshold•2X data has been taken and is being processed for analysis•Plan to take 3 fb-1 total

•CLEO-c: •CLEO III detector with silicon vertex replaced by drift chamber•Covers 93% of solid angle•dE/dx from drift chamber•Ring Imaging Cherenkov Detector (RICH) for particle ID•Track resolution of ~ 0.6%•Solenoid field 1 T


Institute

3/16

Motivation to study BR(D X)

Physics Branching fractions and form

factors by different method Branching ratio not

previously measured for neutrinos

Unique opportunity at CLEOc

Produced at threshold Clean events

Tagged D fully reconstructed

Lepton flavor blind Electrons and muons on

equal footing

Data Event


Institute

4/16Electron and Neutrino Spectra are Different

s

e+

se+

esec

Can look at spins to determine favorable and suppressed directions for neutrino

The top diagram is favored, the neutrino will get a boost from the W+* compared to the electron in the lab frameThe same effect will occur for the anti-c.

W+*

W+*

Low Q2

Low Q2

eEE Low ,High

EEe Low ,High

In B decays electron has harder spectrum than neutrinos, electron is now particle ceb

In weak semileptonic decays of quarks, the lepton has the harder spectrum than the anti-lepton

Q2 = momentum transfer to W


Institute

5/16

DD)3770(

Simple Hadronic Modes

Fully reconstructed tags

Use tag to eliminate half of each event for neutrino reconstruction

•Add up all signal side tracks and unmatched showers

•Use RICH and dE/dx for particle ID

•Get missing 4-momentum

•Cut to eliminate non neutrino events

•KL suppression

•Clean reconstruction cuts

0222 missmissmiss PEMass

SK

KD

K

K

K

D 00

Method of Analysis

Xl


Institute

6/16Emiss vs. E2 - P2

Fully Reconstructed Hadronic events

Not Seen KL

Neutrinos

Red = event with neutrino

Blue = no neutrino in event M

issi

ng

En

erg

y(G

eV

)

222 )(GeVPE missmiss

Monte Carlo

Max M2miss:

P2=0, E vs E2


Institute

7/16

Good Tag Cuts Only 1 tag per mode per event Good Tag

Delta E cut Beam constrained mass cut

Clean Reconstruction Cuts No tracks lost to quality cuts Showers are not matched to track Charge of event is = 0 Costheta of missing momentum is inside detector At least one track in event – no ID performed

KL Suppression Cuts Single Track Cut [event with single kaon]

Track Shower Matching Cut

Cuts


Institute

8/16

KL Suppression Cuts

Missing mass squared for events with KL

Monte Carlo

Energy in showers matched to KL

Monte Carlo

Half of KL’s leave no energy Peak at Missing Mass2 = (.497GeV)2

Other half leave some fraction of their energy in EM calorimeter

No Hadronic calorimeter for KL reconstruction

CC is ~1 nuclear interaction length => about half of KL’s interact in detector

Eshower(GeV)222 )(GeVPE missmiss

2

LKM


Institute

9/16

KL: Shower Distance Cut (Weinberger angle)

Angle of missing momentum vector to closest unmatched shower

20% of events with neutrinos have no shower to measure angle to, this cut is then skipped

Black = KL and no neutrino

Red = Neutrino events with a shower to compare to

Cos(Weinberger angle)

Monte Carlo

Keep these events

Missing Momentum Vector

Closest Shower

Charged tracks

Neutrino Event

Missing Momentum Vector

Charged tracks

KL Event


Institute

10/16

Effect of Cuts on Background

Monte Carlo


Red = neutrino event

Blue = no neutrino in event

Events with good tag

Clean reconstruction cutsTo make sure that event is fully reconstructed and that missing vector is in detector

KL suppression

Mis

sing E

nerg

y (

GeV

)

&

Monte Carlo


Institute

11/16

Effect of Cuts on Background

Mis

sing E

nerg

y (

GeV

)

Monte CarloMonte Carlo

222 )(GeVPE missmiss 222 )(GeVPE missmiss

Red = neutrino event

Blue = no neutrino in event

Events with good tag

Clean reconstruction cutsTo make sure that event is fully reconstructed and that missing vector is in detector

KL suppression

Mis

sing E

nerg

y (

GeV

)

&

Monte Carlo


Institute

12/16

V Cut on Emiss vs. E2 – P2

“V” cut on E2 – P2

E2 – P2 = (E+P)*(E-P) 2E(E-P)

Monte Carlo


Mis

sing E

nerg

y(G

eV

)

Error on Mass2miss is

dominated by error on energy

The “V” cut is then a constant cut on the fractional error of the Mass2

miss

Shower distance cut will not eliminate non-interacting KL


Institute

13/16

Missing Energy Spectra

Emiss(GeV) Emiss(GeV)

D0 D±

Red = signal

Blue = background

Black = all events that pass cuts: sum of red and blue

MCMC

Cutoff at 0.1 due to min P cut


Institute

14/16

Data [57.2 Pb-1] vs. MC Comparisons

MC Data


Mis

sing E

nerg

y (

GeV

)

Mis

sing E

nerg

y (

GeV

)



Institute

15/16

Data vs. MC

D0 D±

Emiss (GeV)

points = data

red = scaled MC

Emiss (GeV)


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16/16

BR(D X): Conclusion

CLEOc allows first opportunity to make measurement of Branching Ratio in this inclusive mode

Fully inclusive as to: Lepton flavor Semileptonic decay mode

This approach is completely orthogonal to all existing measurements of BR(D Xl)


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17/16

EXTRA SLIDES


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18/16Neutrino and No Neutrino EventsOld plots


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19/16

How Well Code id’s Particles

Fixed id in code

Particle ided as

1 = kaon

2 = pion

3 = electron

kaon

electron

pion

No muon id means all muons are treated as pions


Institute

20/16

PDG Fit D0 Average D+ D+ D0PDG BR(D->eX) 17.2 1.9 6.87 0.28PDG BR(D->muX) XXX XXX 6.5 0.8Sum (or e*2 if nu not available) 34.4 3.8 13.37 1.73

PDG(2004) inclusive D lX


Institute

21/16

Left Side Tail

Signal only


Signal only

Mis

sing E

nerg

y(G

eV

)


Institute

22/16

“Left” Event properties

Look at properties of events in “left tail”

Most have one photon

Dashed – left

Solid - good

Photon’s angle is anti-corrolated to MissVec

Appears that photon is double counted


Institute

23/16

Subtract Out Photon

Dashed – left side events

Solid – photon subtracted out

Left side events

Events with photon subtracted out.

Now in signal region


Mis

sing E

nerg

y(G

eV

)


Institute

24/16Re-Fixed Plot

Extra background?


D±

D0

Emiss

Emiss

Mis

sing E

nerg

y(G

eV

)


Institute

25/16

Spike in D+ Bkg

Looking at spike events [no nu, Emiss > 0.72] properties show only one track in event

Decay tree shows events are

D->KLPi, with the Pi missided as a kaon

Bkg pions not in spike

Bkg pions in spike

Signal events

spike

Non spike bkg

Number of tracks in event


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26/16Comparison of MC Generated vs. Reconstructed Variables

Overlay of MC generated energy spectrum of neutrinos

Scaled down to recontructed spectrumBlack = mc generated(scaled)

Red = reconstructed neutrinos

Energy (GeV)

e

Trueee

obs ESESmod

modmod )()(

inclusive measurement of br(d x) and the neutrino spectrum

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