# Presentation: 943758

## NEW CHARM RESULTS FROM FOCUS

- Stefano Bianco
- Laboratori Nazionali di Frascati dell’INFN
- La Thuile - March 3rd, 2004

**NEW CHARM RESULTS FROM FOCUS**

## OVERVIEW

**Measurement of masses and widths of excited charm mesons, and evidence for broad states ****J.M.Link et al. (FOCUS Coll.) hep-ex/0312060 accepted by  Phys.Lett.B**
**Measurement of D****s****+******************** formfactors ****J.M.Link et al. (FOCUS Coll.) hep-ex/0401001 accepted by  Phys.Lett.B**
**K-matrix analysis of charm mesons Dalitz plots ****J.M.Link et al. (FOCUS Coll.) hep-ex/0312040 accepted by  Phys.Lett.B**
-     Sorry, no time to report on  these 2003-2004 results:
-  _Measurements of six body __hadronic__ decays of the D0 charmed meson. _By FOCUS Collaboration  [hep-ex/0401019]
-  _Charm - anti-charm baryon production asymmetries in photon nucleon interactions. _By FOCUS Collaboration  Phys.Lett.B581:39-48,2004
-  _Study of __hadronic__ five body decays of charmed mesons involving K0(S). _By FOCUS Collaboration  [hep-ex/0310051]
- _Study of the decay mode D0 ---> K- K- K+ pi+. _By FOCUS Collaboration Phys.Lett.B575:190-197,2003. [hep-ex/0308054]
-  _Search for rare and forbidden three body __dimuon__ decays of the charmed mesons D+ and D(s)+. _By FOCUS Collaboration Phys.Lett.B572:21-31,2003. [hep-ex/0306049]
-  _Measurements of __Xi__(c)+ branching ratios. _By FOCUS Collaboration Phys.Lett.B571:139-147,2003. [hep-ex/0305038]
-  _Studies of correlations between D and anti-D mesons in high-energy __photoproduction__. _By FOCUS Collaboration Phys.Lett.B566:51-60,2003. [hep-ex/0305018]
-  _Measurement of the Omega0(c) lifetime. _By FOCUS Collaboration Phys.Lett.B561:41-48,2003. [hep-ex/0302033]

- La Thuile 2004

- S.Bianco Laboratori Nazionali di Frascati

##                 Spectrometer at FERMILAB Wide Band Photon  Beam

**Successor to E687. Designed to study charm particles produced by ****~200 GeV photons**** using a fixed target spectrometer with updated  ****Vertexing,**** ****Cerenkov,**** ****EM **** ****Calorimeters,**** and ****Muon id**** capabilities.  Member groups from USA, Italy, Brazil, Mexico, Korea.        **_**DATA COLLECTED IN 1996-1997 **_

- Over 1 million reconstructed!

**                ****Spectrometer at FERMILAB Wide Band Photon  Beam**

- La Thuile 2004

- S.Bianco Laboratori Nazionali di Frascati

**Notes:**
But first  just a few general things about focus.  It ran in the 96 and 97 fnal fixed target run. We analyze the interactions of roughly 200 GeV photons which interact on a segmented BeO target which is roughly 12% of an interaction length.  The first part of our spectrometer consists of 4 planes of Si which are interleaved with the target segments and 12 planes of downstream Si. Charged tracks are momentum analyzed through a 2 magnet spectrometer and tracked by 20 PWC planes. We have ~300 cell threshold Cerenkov counter arranged in three counters (blue).  We also have excellent lepton identification for muon decays and electromagnetic calorimetry gives the ability to identify electrons and reconstruct photons and pizero. The apparatus is roughly  30 meters long.  We ran our beam very hot and accumulated a total charm sample of over 1 million fully  reconstructed Golden Mode charm events.

## Charmed mesons spectroscopy chart (ante Spring 2003)

- In the heavy-quark limit, the heavy-quark
-  spin **S****Q**** ** and the total angular momentum
- of the light-quark **j****q**=**L**+**S** are conserved

- Each level is composed  of a degenerate doublet of states with the same
-  jq and total angular momentum J=jq± 1⁄2.
- jq=1⁄2 states are predicted  to be broad (100-200MeV width).

**THIS PICTURE **
**QUESTIONED BY BABAR**
**AND CLEO DISCOVER OF**
**Dsj. **
- For a recent review see
- SB Fabbri Benson Bigi Hep-ex/0309021

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- S.Bianco Laboratori Nazionali di Frascati

## Processes studied:
N  D0+ X,  D0K-,K-
N  D++ X,  D+K-
Feeddowns:
D1+(jq=3/2)D*0,  D*0D
D2*+D*0,  D*0D
D1+(jq=1/2)D*0,  D*0D

- N  D0+ X,  D0K-,K-
- N  D++ X,  D+K-
- Feeddowns:
- D1+(jq=3/2)D*0,  D*0D
- D2*+D*0,  D*0D
- D1+(jq=1/2)D*0,  D*0D

**Measurement of masses and widths of excited****charm mesons, and evidence for broad states**J.M.Link et al. (FOCUS Coll.) hep-ex/0312060 accepted by  Phys.Lett.B

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- S.Bianco Laboratori Nazionali di Frascati

## D and D* sample

**Processes studied:**
******N ******** D****0****************+ X,  **
**D****0********K******
**D****0******** K******
******N ******** D****+****************+ X, **
** ****D****+********K******
**Remove D******** combinations from D***

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## D0and D+ mass distributions

- reconstruction

- M(D0+)-M(D0)+1.8646 (GeV/c2)

-   Shorthand: 

- Entries / 10 MeV/c2

**D****0****************and D****+**************** mass distributions**

**Wrong sign**

- M(D+--)-M(D+)+1.8693 (GeV/c2)

- Entries / 10 MeV/c2

- Shorthand: 

**Wrong sign**

**Feed down from D****2*********, D****1**** partial **
**reconstruction**

**Combinatoric background**

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## Fitting D0and D+ mass distributions

- D-wave fixed
- to PDG D2* mass and
- width

- 2. D-wave free fit
- parameter

- Bad fits, excess
- of events between D2*
- and the feeddowns

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## Fitting D0and D+ mass distributions

- Add S-wave
- Fit cl=22% now

- Recompute the
- feeddown lineshape
- using the D2* parameters
- measured in Step 3.
- Fit cl=28% now

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## Significance of S-wave excess

- The broad excess observed could be the broad state D0*,
- or the feeddown from a broad D1 state        goto feedown list           .

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## RESULTS

|  | D2*0 | D2*+ | D2*+-D2*0 | “D01/2” | “D+1/2” |
| --- | --- | --- | --- | --- | --- |
| Yield | 5776±869±696 | 3474±670±656 |  | 9810 ± 2657 | 18754±2189 |
| Mass
PDG03
BELLE03 | 2464.5±1.1±1.9
2458.9±2.0
2461.6± 3.9 | 2467.6±1.5±0.76
2459±4 | 3.1±1.9±0.9
0 ± 3.3 | 2407±21±35

2308± 36
 | 2403±14±35 |
| Width
PDG03
BELLE03 | 38.7±5.3±2.9
23±5
45.6± 8.0
 | 34.1±6.5±4.2
25+8-7 |  | 240±55±59

276±66 
 | 283±24±34 |

- Errors on D2* masses and widths smaller than or equal to PDG03
- Agreement with the recent BELLE result (hep-ex/0307021).

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## SYSTEMATICS STUDIES I

|  | D2*0
 |  | D2*+ |  | D2*+-D2*0 | “D01/2 “ |  | “D+1/2” |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  | Mass | Width | Mass | Width | Mass | Mass | Width | Mass | Width |
| L/< 30 | 0.160 | 1.231 | 0.134 | 0.960 | 0.294 | 0.926 | 15.73 | 0.050 | 2.871 |
| Part/Antipart | 1.67 | 0 | 0.53 | 0 | 0 | 0 | 0 | 0 | 31.4 |
| PD < 70GeV/c | 0.227 | 0.705 | 0.392 | 1.983 | 0.165 | 2.482 | 8.509 | 10.38 | 2.500 |
| Different Fits | 0.412 | 0.272 | 0.124 | 0.693 | 0.353 | 10.48 | 43.95 | 1.439 | 8.635 |
| Fit Regions | 0.376 | 0.536 | 0.174 | 0.991 | 0.315 | 1.571 | 12.80 | 1.209 | 6.657 |
| Feed-down tests | 0.633 | 2.373 | 0.262 | 3.289 | 0.443 | 32.71 | 31.91 | 32.45 | 6.137 |
| Binning tests | 0.442 | 0.576 | 0.113 | 0.770 | 0.550 | 6.584 | 6.652 | 6.380 | 0.894 |
| Mass Scale | 0.100 | 0 | 0.100 | 0 | 0.100 | 0.100 | 0 | 0.100 | 0 |
| Total syst. error | 1.94 | 2.89 | 0.76 | 4.2 | 0.91 | 35.1 | 59.0 | 34.7 | 34.0 |

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## SYSTEMATICS  STUDIES II

- Background shapes:
-                                   (E687)
-                                              (L3)

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## THIS RESULT AND THEORY PREDICTIONSPredicted mass differences with respect to the D meson compared to this result

| Reference | D2*
jq = 3/2
3P2 | D1
jq = 3/2
3P1 | D1
jq = 1/2
1P1 | D0*
jq = 1/2
3P0 |
| --- | --- | --- | --- | --- |
| This paper | 599 ± 2 |  |  | 538 ± 39 |
| World Av. | 593 ± 3 | 556 ± 4 |  |  |
| Kalashnikova et al. (2002) | 579 | 562 | 603 | 564 |
| Di Pierro et al. (2001) | 592 | 549 | 622 | 509 |
| Ebert et al. (1998) | 584 | 539 | 626 | 563 |
| Isgur (1998) | 594 | 549 | 719 | 699 |
| Godfrey and Kokoski (1991) | 620 | 590 | 580 | 520 |
| Godfrey and Isgur (1985) | 620 | 610 | 560 | 520 |
| Eichten et al. (1980) | 645 | 637 | 498 | 489 |
| Barbieri et al. (1976) | 428 | 380 | 339 | 259 |
| De Rujula et al. (1976)  | 494 | 464 | 384 | 374 |

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## A long-standing problem: the form factor ratios rv and r2 describing D+K0  should be close to Ds+ since only difference is a spectator
    quark d replaced with a s
Lattice gauge calculations:
    max diff= 10%
Experiment: 
 rv    OK
 r2  inconsistent (3.3.

-     quark d replaced with a s
- Lattice gauge calculations:
-     max diff= 10%
- Experiment:
-  rv    OK
-  r2  inconsistent (3.3.

**New measurements of the ****D****s****+******************** ****form factor ratios **J.M.Link et al. (FOCUS Coll.) hep-ex/0401001 accepted by  Phys.Lett.B

****

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## Form factor formalism for Ds+ 

**D****s****+**

- s

- s

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## Searching for s-wave interference in 

**K*******

- 

**data****ccbar mc**

- events cos **V**

- events cos **V**

- events cos **V**

- FOCUS published observation for a very strong s-wave interfering with p-wave in the K system for D  **K*******
- NO evidence for s-wave interference in Ds 

**data**

**K*******

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## The mKK distribution for   Ds+candidates

**Data (solid) and c****c**** background MonteCarlo (dashed). **
**Main background from**
**D****+********************where**
**a pion is misidentified as a muon**

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## Comparing data and model

- Histogram:data- dots:model-dashed histogram: cc Montecarlo

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## RESULTS

**r****v****=1.549 ± 0.250 ± 0.145**

**r****2****=0.713 ± 0.202 ± 0.266**

- Most precise measurement to date
- very consistent with D+K0
- very consistent with  expectation that the form
- factors for the two processes should be very similar

- Solid green: world av. Ds+ Dashed blue: world av. D+K0

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## Form Factors D+K0  and Ds+ 

- THIS RESULT

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## DP analysis of Ds+ and D+ decay to  using the K-matrix formalism J.M.Link et al. (FOCUS Coll.) hep-ex/0312040 accepted by  Phys.Lett.B  see also : S.Malvezzi Workshop on B physics, Rome Italy January 15, 2004. 

- Dalitz plots have been proved to be a powerful tool in three-body decays, investigating
- Resonant substructure
- Interference patterns
- Final state interactions
- Relationships to light-meson spectroscopy
- Traditionally, isobar formalism used
- Decay amplitude is a sum of Breit-Wigner propagators
- Breit-Wigner amplitudes for a resonance which is broad and overlaps with other resonances can be connected to the pole positions only through models of analytic continuation

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## K-matrix picture

***K*****-matrix picture**

- The amplitude is written as a sum
- The amplitude F takes care of S-wave component by integrating over the scattering amplitudes of the five  virtual states K,’,

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## “K-matrix analysis of the 00++-wave in the mass region below 1900  MeV’’

**“****K-matrix analysis of the 00++-wave in the mass region below 1900  MeV’’**
-           V.V Anisovich and A.V.Sarantsev  Eur.Phys.J.A16 (2003) 229

** ****To describe the scattering a global fit  to all available**
** ****data was performed**

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## FOCUS D s +  ++- analysis

- Yield Ds+ = 1475 50
- S/N Ds+ = 3.41

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## First fits to charm Dalitz plots

** ****in the *****K*****-matrix approach**

- C.L  fit 3 %

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## in charm hadronic decays 

**No significant direct three-body-decay component**

**No significant  ********(770) ******** contribution**

- Marginal role of annihilation
- in charm hadronic decays

**But need more data!**

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##  D+ ++- analysis   

- Yield D+ = 1527 51
- S/N  D+ = 3.64

** ****D****+******** ********+********+********- ****analysis****   **

- Sideband

- Signal

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## K-matrix fit results

- C.L fit 7.7 %

***K*****-matrix fit results**

- Low mass  projection

- High mass  projection

**No new resonance  required not present in the  scattering.**

**decay channel**** **

**phase (deg)**

**fit fractions (%)**

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## SUMMARY AND CONCLUSIONS

-  New precise measurements of mass and widths of D2*+ and D2*0, with errors better than or equal to PDG03
-  Evidence for broad states in D+ and D0 final states
-  Puzzle of  Ds+****** ** form factors discrepancy solved with  new precise measurement
-  First DP analysis of Ds+,D**+******** ********+********+********-**** **charm decays using K-matrix formalism
- Use information from light-quark scattering experiments (five virtual channels considered K,’,CONCLUSIONS:
- Non-resonant components are described by known two-body S-wave dynamics
- Negligible role of annihilation diagram in Ds ****** ********+********+********–**** **
- Possible applications in B(not discussed here)
- DP analysis of Ds+,D**+******** ********+********+********-**** **charm decays using traditional isobar model is also in progress to compare to K-matrix model.

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## How can we formulate the problem?

- characterized by narrow and well-isolated resonances, we know
- how.

**How can we formulate the problem?**

**The problem is to write the propagator**
** ****for the**** ****resonance ****r **

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