# Presentation: 728164

## Heavy Flavor Production and Spectroscopy at DØ

- Ike Hall
- University of Oklahoma

## Outline

- Upsilon(1S) production cross section
- extended out to rapidity<1.8
- B-> μ ν D**
- B-> μ ν Ds1(2536)
- First high precision, high statistics measurements of semileptonic branching ratios
- Measurement of narrow B** states
- Observation of X(3872)

## The Run II DØ Detector

## Trigger

- All analysis covered in this talk utilized "Bread and Butter" single- and di- muon triggers.

## Upsilon(1S) Production

- Upsilon(1S) production is a good test of heavy quark production models.
- all bbbar states produced directly at the Tevatron
- ~50% of Upsilon's are produced directly
- the rest are due to decay of higher mass states
- eg:Υ(2S)->Υ(1S)ππ
- Aim to significantly extend the CDF Run I measurement out to rapidity of 1.8, as a function of Upsilon pT

## Upsilon Data

- Data was collected using unprescaled scintillator only dimuon trigger.
- Sample Selection
- Quality Cuts:
- Muons required to have hits in all 3 muon system layers
- Track match
- at least 1 silicon hit
- kinematic cuts:
- Muons required to have opposite sign
- pT > 3GeV
- |η| < 2.2
- at least one isolated muon

## Upsilon(1S) signal

**Signal:** 3 Gaussians: Upsilon(1S),(2S),(3S)
- mass/width of (2S) and (3S) fixed
- m2S/3S = m1S + (m2S/3S – m1S)PDG
- σ2S/3S = (m2S/3S/m1S) * σ1S
- determined by monte carlo and J/ψ sample

- Shown plots: 4GeV < pT < 6GeV

- 0 < |y| < 0.6

- 0.6 < |y| < 1.2

- 1.2 < |y| < 1.8

## Upsilon Cross Section

- Normalized upsilon cross section
- as function of pT
- Very little difference in shape as
- a function of rapidity.

- theory curves plotted are derived from
- Berger, Qiu, and Wang
- Phys. Rev. D **71** 034007
- hep-ph/0411026

- Results: dσ(Υ(1S))/dy × *B*(Υ(1S)) → μ+μ-

- 0.0 < |yΥ| < 0.6          732 ± 19 (stat) ± 73 (syst) ± 48 (lum)  pb
- 0.6 < |yΥ| < 1.2          762 ± 20 (stat) ± 76 (syst) ± 50 (lum)  pb
- 1.2 < |yΥ| < 1.8          600 ± 19 (stat) ± 56 (syst) ± 39 (lum)  pb
- 0.0 < |yΥ| < 1.8          695 ± 14 (stat) ± 68 (syst) ± 45 (lum)  pb

- CDF Run I: 680 ± 15 (stat) ± 18 (syst) ± 26 (lum) pb

## Comparison to previous results

- Ratio of most central rapidity
- bin cross section to most forward
- rapidity bin

- Pythia

**ACCEPTED BY PRL!**
**hep-ex/0502030 **

## B-> μ ν D** + X

- D** are orbitally excited D meson states
- In Heavy Quark limit, we expect 2 sets of doublet states
- 2 broad states that decay through S-wave
- 2 narrow states that decay through D-wave
- we look for narrow D** states in semileptonic B decays:
- D01(2420) -> D*+ -
- D*02(2460) -> D*+ -
- One of decay channels

## D0/D*+ data sample

- Started with B-> D0X sample recorded through single muon triggers
**B -> ****μ****+**** D****0**** X**
**D****0**** -> K****+****π****-**
- added additional pion to find D*0
- pTπ > 0.18 GeV
- right sign correlation with muon

**Mass difference window**
**[0.142 – 0.149]**

## D** Selection

- D** selections
- Additional pion
- pT > 3 GeV
- at least 1 SMT hit
- correct charge correlation
- Impact parameter significance cut
- B selections:
- 5 CFT hits for all tracks
- vertex chi2 requirement
- Lxy significance requirement

## D** signal

- see merged D01 - D*02 signal in D*-π+ invariant mass spectrum

## Branching Ratio measurement

- Measure Br of B  narrow D** X
- Normalize to known Br (B  D*+   X)

-    **Br(B ******** {D****1****0****,D****2*********0****} ******** ******** X) ******** Br(****{D****1****0****,D****2*********0****} ******** D*****+**** ********-****) = **
**             **
**                 ****0.280 ******** 0.021 (stat) ******** 0.088 (syst) % **

- Largest systematic contributions:
- dependence on pTπ**
- effects of possible contribution from wide resonance
- Can be compared to LEP measurement of total D** Br
- ~ half of the rate goes through narrow states

## Future D** measurements pending

- Sample has very good purity.
- Many other measurements can be made with this sample
-                      predicted to be 0.4-0.7 by HQET
- world average 0.4 ± 0.15
- Br ( B -> D1X)
- Br ( B -> D*2X)
- results coming soon with 460 pb-1! (pre-print available in a matter of days)

## Bs -> μνDs**

- Very similar procedure to D** measurement just a different final state.

- Due to the choice of final state,
- very little contribution from
- Ds2(2573) is expected

- We use the same D0 and D*+ sample
- that was used in D** analysis, but
- this time with 460 pb-1

## D0/D* Sample (460 pb-1)

- ~235000 D0s in mass window:
- 1.75<M(D0)<1.95 GeV

- ~52000 D* events in window
- 0.142<M(D*)-M(D0)<0.149 GeV

## K0s in sample

- Made cuts on K0s decay length (>0.5 cm)
- dl cut removes 52% of background
- only 19% of signal removed

- wind up with 5900 K0s

## Selection cuts for Ds1(2536)

- Mass window constraint on D0,D*+, and K0s
- pT KS0 > 1 GeV
- Decay length of KS0>0.5 cm

- Fit to gaussian plus exponential with
- threshold cutoff.
- Fit yields 20 ± 5.6 events (3.7 sigma
- significance)
- M(Ds1(2536)) = **2.536 +/- 0.001 GeV**
- Gaussian width = 2.6MeV

- Demonstrates that signal is observable
- Work in progress to measure
- Br(Bs→D**μν)

## B**

- b-meson spectrum is not yet well established
- Only B± , B0, Bs and B* are considered "established"
- B** states are not well established experimentally
- 2 narrow states B1 (JP = 1+) and B*2 (JP = 2+) decay via D-wave
- 2 wide states B*1w (JP = 0+) and B*2w (JP = 1+) decay via S-wave; too wide to be observed
- B** have only been observed as wide structure in semi-exclusive decays
- mass, width and mass splitting of B** states are not known, but are predicted with good precision by various models.

## B** search

- Search for narrow B** states decaying into B(*)π in 3 channels
- B± -> J/ψ K+
- Bd -> J/ψ K*0
- Bd -> J/ψ K0s
- Signal is searched for in ∆M = M(Bπ) – M(B)
- B* is not explicitly reconstructed, as it is expected to decay to B γ with ~100% probability
- however, because the mass difference between B* and B is ~46 MeV, we expect to see a shift of 46 MeV  in ∆M for decays involving B*
- B1 can only decay to B*π due to angular momentum and parity conservation
- B*2 is expected to decay to both Bπ and B*π with 1:1 proportions predicted by theory.

## B signal

- 2826±93 evts

- 7217±127 evts

- 624±41 evts

## B** search

- data is fit to 3 peaks in ∆M (Relativistic B-W convoluted with gaussian)
- M(B1)-M(B*)
- M(B*2)-M(B*)
- M(B*2)-M(B) (~46 Mev from peak 2)

- Bdπ channel

- We see a complicated mass
- structure from ∆M~405-470 MeV
- in each channel.

## B**

-    Because the mass difference between B+ and Bd is negligible with respect to experimental resolution (<1 MeV), channels can be combined

- 536±114(stat) events
- ~7σ significance
- M(B1) = 5724 ± 4 MeV
- M(B*2)-M(B1) = 23.6 ± 7.7 MeV
- Γ=Γ1=Γ2=23 ± 12 MeV
- All errors statistical

**FIRST DIRECT MEASUREMENTS!**

## X(3872)

- X(3872) first observed by Belle
- B+ -> X(3872) K+
- X(3872) -> J/ψ π+ π-
- quark content still not established
- Search was done at DØ in this mode in ~225 pb-1 of data
- ψ(2S) was used as calibration/comparison channel

## X(3872) sample

- for a variety of reasons, the optimization of cuts on the X(3872) were not possible
- no believable MC
- no reason to believe that kinematics of X(3872) and ψ(2S) are similar
- Cuts chosen to keep a reasonable ψ(2S) signal while reducing background in X(3872) signal region.
- at least 1 SMT hit for 2 of 4 tracks
- ∆R for both pions w.r.t J/ψ π π <0.4
- pTπ > 0.7 GeV

## X(3872)

- 522 ± 100 X(3872) events fitted
- ∆M = 0.7749 ± 0.0031(stat) ± 0.0030(syst)
- main source of systematic error due to mass correction

## X(3872) vs. ψ(2S)

- Break sample into 2 bins of several production and decay variables and compare the fractional yield of X(3872) and ψ(2S)
- Break point chosen to keep ~50% of total sample in each bin, or at physically informative value
- pT(J/ψ) < 15 GeV
- |y| < 1
- dlxy < 0.01 cm
- iso0.5 = 1
- cos(Θπ) < 0.4
- cos(Θμ) < 0.4

## Comparison

- In properties observed, we see no significant differences between X(3872) and ψ(2S)
- These comparisons will become useful as models of X(3872) production advance

- pT >15

- |y|<1

- cos(Θπ) < 0.4

- iso = 1

- dl < 0.01

- cos(Θμ) < 0.4

## X(3872) Future measurements

- measurements are in the works right now using about twice the luminosity
- prompt fraction
- X(3872) -> J/ψ γ
- All other interesting decay modes predicted by any model requires at least 1 neutral particle in the final state.  This measurement is a stepping stone
-  Mππ spectrum

## Conclusion

- Heavy flavor results are starting to come out of DØ
- Upsilon (1S) cross section extended to |y|<1.8
- Narrow D** states observed.  Measurements coming soon
- Ds1(2536) observed.  Measurements in progress
- Narrow B** states observed and measured
- First direct measurements
- X(3872) observed, compared to ψ(2S)
- Stay tuned... We've only just begun.