D - Fermilab

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D - Fermilab

Eric Vaandering – Charmed Hadron Spectroscopy – p. 1/18

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Charmed Hadron Spectroscopy

from FOCUS

XXXIXth Rencontres de Moriond:

QCD and High Energy Hadronic Interactions

28 March – 4 April 2004

Eric W. Vaandering

ewv@fnal.gov

Vanderbilt University

and

FOCUS Collaboration


Eric Vaandering – Charmed Hadron Spectroscopy – p. 2/18

Overview

• FOCUS Experiment

• Photoproduction of charm

Fermilab, 1996–1997

• The L = 1 orbitally excited D states

• D ∗+

2 , D ∗0

2 → Dπ ± measurements plus evidence for D ∗ 0

contributions

• D + s (2317) → D + s π0 observation

• Masses and widths for L = 1 D sJ → DK


Eric Vaandering – Charmed Hadron Spectroscopy – p. 3/18

FOCUS Spectrometer

Target

Silicon

Silicon Microstrips

Beam

Direction

E831

F0cus

Spectrometer

Targets

Trigger Counters

Target Region

Outer

Electromagnetic

P.W.C.'s Calorimeter

Magnet

Outer Muon

R.P.C.'s

Cerenkov

Counter

Inner

Electromagnetic

Calorimeter

P.W.C.

Hadron

Calorimeter

Muon

Hodoscope

Beam

Direction

Straw

Tubes

Highlights:

• Segmented target

• Silicon vertexing

• MWPC tracking

Trigger P.W.C.

Hodoscope

Cerenkov

Counters

Magnet

Trigger

Hodoscope

Beam

Calorimeter

Muon Filter

• Threshold Čerenkov

• EM/hadronic calorimeters

• Muon detectors


P-wave Charmed Mesons

• L = 1 between c and light quark (u, d)

• HQET: j light = s light + L, approximately good

quantum number if m c ≫ Λ QCD

• Idealized picture is doublet of doublets

No spin

j light J P Decays Γ(MeV) Observed

m c ≫ Λ QCD

3/2 2

m c → ∞

+ D ∗ π, Dπ ≈ 20 D ∗+

2 , D ∗0

2 , D ∗+

s2

3/2 1 + D ∗ π ≈ 20 D + 1 , D 0 1 , D + s1

1/2 1 + D ∗ π 100 Latest

1/2 0 + Dπ 100 Observations

Heavy quark symmetry determines decay modes:

• j l = 3/2 dominantly D-wave , j l = 1/2 dominantly S-wave

Reminder: D and D ∗ form j light = 1/2 doublet:

• D: J P = 0 − , D ∗ : J P = 1 − Eric Vaandering – Charmed Hadron Spectroscopy – p. 4/18


Eric Vaandering – Charmed Hadron Spectroscopy – p. 5/18

L = 1 Charm Decays

MeV c 2 L = 0 L = 1

2800

P

J =

J =

q

0 -

0

1 - 0 + 1 + 1 + 2 +

1

1

2

1

2

3

2

3

2

2600

D ’ D *’

2400

2200

2000


ρ

ππ

π

π

π

γπ

π

ρ

π

π

π

* D2

D1

*

D1

D0

ππ

π π π

S - wave

D *

P - wave

1800

D

D - wave


Eric Vaandering – Charmed Hadron Spectroscopy – p. 6/18

What’s overly simplified?

• Doublets may overlap (which 1 + is more massive?)

• Is suppression of S-wave widths complete?

• D s1 right at threshold for D ∗ K

• Very narrow, Γ < 2.3 MeV/c 2

• Data suggests mostly S-wave

• Big surprise, new D s states below D (∗) K threshold

• How do they fit into this picture?


Eric Vaandering – Charmed Hadron Spectroscopy – p. 7/18

D Samples for D 2 Measurement

Photoproduction gives

sizable yields with low

multiplicity

Processes studied:

• γN → D 0 π + + X

• D 0 → K − π +

• D 0 → Kπππ

• γN → D + π − +X

• D + → Kππ

Remove any D 0 candidate

with D ∗ < 3σ.

(Cleans up D 0 π + .)

Number of Events/5 MeV/c 2

Number of Events/5 MeV/c 2

40000

35000

30000

25000

45000

D 0 → K − π + D +

40000 c) → K − π + π +

35000

30000

a)

20000

15000

10000

5000

0

1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1

25000

20000

210K

Number of Events/5 MeV/c 2

25000

20000

15000

10000

5000

0

1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1

M(K - π + ) GeV/c 2

M(K - π + π + ) GeV/c 2

35000

35000

D 0

30000 b)

→ K − π + π + π − D

d)

∗ → D 0 π +

30000

200K

15000

10000

5000

0

1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1

Number of Events/0.5 MeV/c 2

125K

25000

20000

15000

10000

5000

0

0.14 0.142 0.144 0.146 0.148 0.15

M(K - π + π + π - ) GeV/c 2

M(D 0 π + )-M(D 0 ) GeV/c 2


Eric Vaandering – Charmed Hadron Spectroscopy – p. 8/18

D 0 π + and D + π − Distributions

Number of Events/10 MeV/c 2

Feed-downs from D ∗ 2, D 1 → Dπ ± π 0 partially reconstructed

3500

3000

2500

2000

1500

1000

500

3500

3000

2500

2000

1500

1000

500

0

b)

2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3

Fit

E687 Background function

S-wave D 0

*+

D-Wave D 2

*+

Feed-down D 2

*+

Feed-down D 1

+

Number of Events/10 MeV/c 2

2500

2000

1500

1000

500

2500

2000

1500

1000

500

0

a)

2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3

Fit

E687 Background function

S-wave D 0

*0

D-Wave D 2

*0

Feed-down D 2

*0

Feed-down D 1

0

0

2.5 3 3.5 4 4.5 5

∆M +

GeV/c 2

0

2.5 3 3.5 4 4.5 5

∆M 0

GeV/c 2

D + π − (∆M 0 ) and D 0 π + (∆M + ) distributions. D mass is

subtracted and PDG mass added. All parameters fixed at PDG

values, only normalizations float. Clearly not a good match.

Exponential BG matches very well except in signal region.


Eric Vaandering – Charmed Hadron Spectroscopy – p. 9/18

Fitting without D ∗ 0 Broad States

Number of Events/10 MeV/c 2

3500

3000

2500

2000

1500

1000

500

3500

3000

2500

2000

1500

1000

500

0

d)

2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3

Fit

E687 Background function

S-wave D 0

*+

D-Wave D 2

*+

Feed-down D 2

*+

Feed-down D 1

+

Number of Events/10 MeV/c 2

2500

2000

1500

1000

500

2500

2000

1500

1000

500

0

c)

2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3

Fit

E687 Background function

S-wave D 0

*0

D-Wave D 2

*0

Feed-down D 2

*0

Feed-down D 1

0

0

2.5 3 3.5 4 4.5 5

∆M +

GeV/c 2

0

2.5 3 3.5 4 4.5 5

∆M 0

GeV/c 2

Perform a free fit just of D ∗ 2 parameters. Feed-downs are

calculated from PDG values. Still very poor agreement

(χ 2 /d.o.f ≈ 3) between D ∗ 2 signal region and the feed-down

region. D ∗ 2 parameters are far from expected values.


Eric Vaandering – Charmed Hadron Spectroscopy – p. 10/18

Adding D ∗ 0 Broad States

Number of Events/10 MeV/c 2

3500

3000

2500

2000

1500

1000

500

3500

3000

2500

2000

1500

1000

500

0

b)

2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3

Fit

E687 Background function

S-wave D 0

*+

D-Wave D 2

*+

Feed-down D 2

*+

Feed-down D 1

+

Number of Events/10 MeV/c 2

2500

2000

1500

1000

500

2500

2000

1500

1000

500

0

a)

2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3

Fit

E687 Background function

S-wave D 0

*0

D-Wave D 2

*0

Feed-down D 2

*0

Feed-down D 1

0

0

2.5 3 3.5 4 4.5 5

∆M +

GeV/c 2

0

2.5 3 3.5 4 4.5 5

∆M 0

GeV/c 2

Add S-wave contribution for D ∗ 0 state (j l = 1 ). Fit is much

2

improved, especially problem region before. CL = 22%. Also

could be D ∗ 1 (j l = 1) → D ∗ π with an unreconstructed π 0 .

2


Eric Vaandering – Charmed Hadron Spectroscopy – p. 11/18

Final D 0 π + and D + π − fits

Number of Events/10 MeV/c 2

3500

3000

2500

2000

1500

1000

500

3500

3000

2500

2000

1500

1000

500

0

d)

2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3

Fit

E687 Background function

S-wave D 0

*+

D-Wave D 2

*+

Feed-down D 2

*+

Feed-down D 1

+

Number of Events/10 MeV/c 2

2500

2000

1500

1000

500

2500

2000

1500

1000

500

0

c)

2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3

Fit

E687 Background function

S-wave D 0

*0

D-Wave D 2

*0

Feed-down D 2

*0

Feed-down D 1

0

0

2.5 3 3.5 4 4.5 5

∆M +

GeV/c 2

0

2.5 3 3.5 4 4.5 5

∆M 0

GeV/c 2

For consistency, we re-simulate the feed-down shapes with M, Γ

found previously. CL of fit increases to 28%, central values

basically unchanged.


Eric Vaandering – Charmed Hadron Spectroscopy – p. 12/18

Systematic Checks

Signals are fit with relativistic Breit–Wigner ⊕ experimental

resolution. BG is exponential + roll-over: e a+bx (x − c) d .

Studied a large number of similar backgrounds (wrong sign, D

sidebands, simulations). All are consistent with single

exponential beyond 2250 MeV/c 2 .

Studied alternative BG parameterizations too. S-wave

contribution is needed for an acceptable fit. Many other

systematic studies on fitting method and significance of S-wave.

In addition, circumstantial evidence that S-wave contribution is

not dominated by feed-down from D 1 (j l = 1 2 )

• Ratios of D ∗ 0/D ∗ 2 for both charges make sense (Feed-down

should be larger for D 0 π + since D ∗0 ↛ D + )

• Fit parameters of two broad states are consistent


Eric Vaandering – Charmed Hadron Spectroscopy – p. 13/18

D 0/+ π ± Results

D ∗0

2 D ∗+

2 D ∗+

2 − D ∗0

2

Yield 5776 ± 869 ± 696 3474 ± 670 ± 656 —

Mass 2464.5 ± 1.1 ± 1.9 2467.6 ± 1.5 ± 0.8 3.1 ± 1.9 ± 0.9

PDG03 2458.9 ± 2.0 2459 ± 4 0.0 ± 3.3

Belle03 2461.6 ± 3.9

Width 38.7 ± 5.3 ± 2.9 34.1 ± 6.5 ± 4.2

PDG03 23 ± 5 25 +8

−7

Belle03 45.6 ± 8.0

“D ∗0

0 (j l = 1 2

)” “D

∗+

0 (j l = 1 2 )”

Yield 9810 ± 2657 18754 ± 2189

Mass 2407 ± 21 ± 35 2403 ± 14 ± 35

Belle03 2308 ± 36

Width 240 ± 55 ± 59 283 ± 24 ± 34

Belle03 276 ± 66

Errors on D ∗ 2 masses and widths smaller than or same as PDG03

and agree with recent Belle report (hep-ex/0307021).


Eric Vaandering – Charmed Hadron Spectroscopy – p. 14/18

Excited D s Mesons

Until spring 2003, this pattern was expected to be repeated in the

D s sector. Two relatively narrow j light = 3/2 states had been

observed and broad j light = 1/2 were expected to be there too.

Instead, two new, very narrow states have been observed by the

B factories decaying to D (∗)

s π 0 .

The first, dubbed D ∗ sJ(2317), was discovered by BABAR and

later confirmed by CLEO and Belle.

The second, D ∗ sJ(2463), was discovered by CLEO and confirmed

by BABAR and Belle.

D ∗ sJ(2317) also seen by FOCUS

For j l = 3/2 states, analysis is very similar to D sector; replace

π with K + /K 0 S.


Eric Vaandering – Charmed Hadron Spectroscopy – p. 15/18

D + s (2317) Observation

Preliminary

• Reconstructed in D + s (→ K − K + π + )π 0 (58 events, inner

EM Cal only)

• Correction to π 0 energy based on D ∗ s → D + s π 0 and

D 0 → K − π + π 0 .

• Mass (using PDG D + s value) found to be

2323 ± 2 MeV/c 2 . BABAR/Belle/CLEO avg. ∼ 2317


Eric Vaandering – Charmed Hadron Spectroscopy – p. 16/18

D + sJ (2573) → D 0 K + and D + K 0 S

Simultaneous fit to D 0 K + and

D + K 0 S . Terms:

Preliminary

• D ∗ s2 signal: D-wave Rel. BW

• Smooth BG shape

• D s1 & D ∗ s2 feed-down shapes

Common M and Γ, stat. only.

• M = 2567.3 +1.3

−1.2 MeV/c 2

• Γ = 28.5 +4.8

−4.0 MeV/c 2

PDG values are:

First observation of D + K 0 S decay mode.

Comparable errors to PDG averages

• M = 2572.4 ± 1.5 MeV/c 2

• Γ = 15 ± 5 MeV/c 2


Eric Vaandering – Charmed Hadron Spectroscopy – p. 17/18

D + s1 (2536) → D ∗+ K 0 S

Terms in fit:

Preliminary

• D s1 signal: Non-rel. BW

convoluted with Gaussian

• Smooth background shape

• D ∗ s2 signal: D-wave Rel. BW

Measure M(D + s K 0 S) − M(D + s )

• ∆M = 525.1 ± 0.3 MeV/c 2

• Γ = 1.6 ± 1.0 MeV/c 2

Statistical errors only. PDG values:

• ∆M = 525.35±0.34 MeV/c 2

• Γ < 2.3 MeV/c 2 @ 90% CL

Very near threshold → narrow (≪ 20 MeV/c 2 ) width

D s2 → D ∗+ K 0 S

is not significant, but interesting.


Eric Vaandering – Charmed Hadron Spectroscopy – p. 18/18

Conclusions

• New precise measurements of D ∗+

2 and D ∗0

2 masses and

widths. Errors comparable to PDG averages. Published as

PLB 586 (2004) 11–20.

• Same paper presents evidence for broad (D ∗0

0 ) states in

D + π − and D 0 π + final states (first evidence in D 0 π + ).

• Combined paper on excited D s states in preparation.

• D ∗ π ± under study for other L = 1 states.

• Renewed interest in sector due to “strange” charmed

mesons

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