Beach04 Chicago Peter Kluit Excited B states at LEP Peter Kluit (NIKHEF) DELPHI/LEP Introduction & history Theory Experimental overview Excited B u,d results

Beach04 Chicago Peter Kluit

Excited B states at LEP

Peter Kluit (NIKHEF)

DELPHI/LEP

• Introduction & history • Theory• Experimental overview• Excited Bu,d results• Search for Bs

** and b(*)

• Summary


Introduction History

Boom of B physics at LEP

around 1994

• vertex detectors

• exclusive reconstruction

Discovery Bs meson at LEP

B baryons

Precision lifetimes

Bd oscillations Event Bs→ `→KK


Inclusive B reconstruction

New technique (~1994)

• High rapidity particles

• Secondary vertex

• Energy-momentum constraint

Estimate B four-momentum

Physics result:

precision mass B*→B

Production V/(V+P)=0.75

→e+e-


Discovery of excited B states

Reconstruct B**→B

Inclusive B

fragmentation

OPAL 1995

Prel. 1997

Prel. 1997

Bs**b

(*)

OPAL 1995

1995


Theory HQET

l jq JP state Decay

0 ½ 0-

1-

BB* B

1 ½ 0+

1+

B*0

B*1

BB*

1

3/2

1+

2+

B1

B*2

B*B(*)

Heavy Q, light quark q

sq l → jq; sQ jq → J

Charm system measured:

Broad

NarrowExpect B systemm doublet ~mc mc/mb

~13 MeV

Broad y 300 MeV

• Similar for Bs**, decay to Bs* Isospin forbidden

• Dominant decay Bs**→ B(*) K, if above threshold


B production at LEP

production fractions adjusted to world average


Experimental overview Bud**

Experiment method m(B**) MeV (B**)/(b) OPAL 95 Incl 5712 ± 11 0.22 ± 0.05 DELPHI 95 Incl 5732 ± 5± 20 0.27±0.02±0.06

ALEPH 96 Incl 5734 ± 3 ± 16 0.14±0.01±0.03

L3 99 Incl B*2: 5768±5±6 0.32±0.03±0.06

CDF 01 Semi-excl B1: 5710 ± 20 0.22±0.05±0.02

ALEPH 98 Excl B*2:5739±11±6 0.24±0.07±0.05

Some numbers recomputed

using common inputsOPAL 01 Br(B**→B* X)=0.85±0.26±0.12

Narrow states


Experimental issues

• Crucial treatment of background

• Taken from MC, except ALEPH exclusive analysis

• Induces high production rate, shifted mass peaks, instabilities

ALEPH exclusive


New DELPHI B** analyses

Focus on the background

• using control sample: High efficiency

• Reduction by neural networks: High purity

Full LEP I statistics, reprocessed data, improved analysis techniques, inclusive B reconstruction

b and anti b tagging

B charge


Analyses steps

• Reconstruct weakly decaying B and combine with from primary vertex

Signal Background wrong sign

Bd** →B+ B+

Bu**+ →B0 B0

• Samples separated b/b tag B vertex charge

• High Efficiency: soft cuts, signal/wrong sign similar shape

• High Purity: tight cuts, neural network


High efficiency Analysis• Simultanous fit to signal and background

B** signal

Narrow: B*2 mass and m(B*2-B1) free

Br(B*2 →B*/B±0.3

Broad: extrapol from Charm

m(B*1)=m(B1),m(B1-B0)=45 MeV

=300(330) MeV

Enhancement at Q~500 MeV, ~300 MeV (~2 s.d.)

DELPHI


High purity analysis• Fit background MC times polynome

• Signal resolution free parameter

Largest Systematics

• Background parametrisation

• Energy scale

• Cuts NN rapidity

• Modeling:

With/without 500-state

Spin/state counting

Fits not sensitive to Broad states and to spin/state counting (< 2 s.d.)

Significant deviations MC

at low and high Q values

B0

B+


Summary of B** results• Total rate (B**ud)/(b) (broad+narrow)

Meth Total rate Narrow rate Q( B*2 ) MeV

m(B*2-B1) MeV

HEff 0.160±0.012

±0.020±0.025

0.091±0.007

±0.013±0.011

316±9

±12±9

-2±15±9±11

HPur 0.153±0.017

±0.038±0.017

0.088±0.009

±0.022±0.011

323±7

±13±9

15±13±10±6

Comb 0.157±0.011

±0.022±0.019

0.090±0.007

±0.013±0.011

319±6

±9 ±9

6±11±7±6

(stat) (sys) (model)

m(B*2)=5738 ± 14 MeV and m(B1)=5732 ± 20 MeV

DELPHI preliminary


Comparison of LEP Results• Rate (B**ud)/b) (narrow)~factor 1.5-2 lower

• Due to background treatment, inclusive analyses at LEP overestimate the rate

• Compatible with ALEPH exclusive analysis

m(B*2)=5739 ± 10 MeV DELPHI:5738 ± 14 MeV

Total rate=0.24±0.07±0.05 DELPHI:0.157±0.011±0.029

• Compare to (D**narrow)/(c) = 0.17 ±0.05

• FUTURE recommend exclusive analyses extracting the background from data


DELPHI B**s search • Channel Bs

** → B(*)+ K-

•Using neural networks for identification of kaon and B vertex charge

•Fit signal (Gaussian), free background

Total Significance 3.8

systematics included

•Background shape

•Identification K/ NN

•Energy scale


Interpretation & discussion• Most likely Bs2

* → B K-

(B*K reduced by factor 10)

Bs1 Puzzle: Large m? Enhanced Bs1 → Bs*?

Results m(Bs2*)=5852 ± 5 MeV OPAL: 5800-5900 MeV

Rate (Bs2*)/(b)=0.0093±0.0020±0.0013 OPAL: 0.020 ±0.006

Where is Bs1 → B*K?

m 13 MeV

DELPHI preliminary


DELPHI b(*) search

• Channel b± (*)→b±

• Using neural networks for identification B baryon

• Fit signal, free background

Sqq J

b 0 ½b 1 ½b

* 1 3/2

Upper limit 95% CL

(b(*))/(b) < 0.012

Preliminary

Old prel. DELPHI result

not confirmed


Summary• New DELPHI measurements for B**ud

Total production rate: (B**ud)/(b)=0.157±0.011±0.029

m(B*2)=5738 ± 14 MeV and m(B1)=5732 ± 20 MeV

New results ~factor 1.5-2 lower than previous due to background

Compatible with ALEPH exclusive, and charm production

• Search for B**s

Signal at 3.8 with m(Bs2*)=5852 ± 5 MeV; Bs1 Puzzle

Production rate: (Bs2*)/(b)=0.0093±0.0020±0.0013

• Search for b(*)

Limit production rate:(b(*))/(b) < 0.012 at 95% CL

Pre

limin

ary

Documents

Beach04 Chicago Peter Kluit Excited B states at LEP Peter Kluit (NIKHEF) DELPHI/LEP Introduction & history Theory Experimental overview Excited B u,d results