# Presentation: 935059

## Study of  DS+η system

**They look in particular at D and ****D****S**** combinations with photons:**
**Nothing special with D meson yet**
**With recent discoveries of ****D****S****(2317,2457) there are more chance with ****D****S****, so...**

**Study of  ****D****S****+****η system**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of  DS+η: look in DS + η    γ γ

**Mass = 2640 MeV**
**Width = 15 MeV**
**          ****S/****√****B = 8 ****σ**

**Mass of ****D****S**** +****η, GeV**

**Combinations/20 MeV**

**Δ**** M(****η)  = ± 80 MeV, E****γ****> 3.2GeV, **

**cos(Θ****η*********) >-0.9**

**Peak width compatible**

**with mass resolution**

**CUTS:**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of  DS+η: DS +πo 

**S/****√****B = 3.5 ****σ**

**Mass of ****D****S**** +****πo, GeV**

**Combinations/20 MeV**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of  DS+η: DS+γ

**S/****√****B = 7 ****σ**

**Study of  ****D****S****+****η: D****S****+****γ**

**Combinations/10 MeV**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of  DS+η: start look at DS

**Combinations/10 MeV**

**Mass, ****GeV**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of  DS+η: look at πo and η

**Combinations/4 MeV**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of  DS+η: look at γ, πo and η 

**(no cuts on γ multiplicity!)**

**E****γ****, GeV**

**γγ**** mass, GeV**

**πo**

**η window**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of  DS+η: improvements, selections, cuts

**New non-linearity tables**
**Two versions of analysis give similar results :**
**     ****recon for neutral particles**
**     ****hand made neutrals – **
**Cuts**** on γ**** energies (see plots);**
**     ****γ-s from πo window are excluded **
**     ****backward angles of η emission in D****S****+****η C.M.S. (Θ****η*********) are excluded **
** ****Constrains ****on ****D****S****, ****η ****and ****πo ****masses **
**Note: about 10% of events have double entries in the plots**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of  DSη(2640): side-band study

**M(KK ****π)**

**M(γγ)**

**Detailed study by I. Larin**
**       ****(see appendix)**

**None**

**None**

**None**

**None**

**None**

**None**

**None**

**Signal**

**bump?**

**D****S**** mass**

**(D****S****η-D****S****)mass**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of  DSη(2640): peak of η in γ γ-mass distribution in DS mass window

**S/****√****B ~ 4****σ**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of  DSη(2640): peak in η-mass gates

**Isotropy**

**Forward asymmetry**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of  DSη(2640): η angular distribution in C.M.S

**Isotropy**

**Forward asymmetry**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of  DSη(2640): possible influence of DS(2112)

**Mass of ****D****S**** +****η, GeV**

**No ****D****S****(2112) window for ****γ**

**With ****D****S****(2112) window for ****γ**

**Combinations/25 MeV**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of DSη(2640): η   3π

**Mass of ****D****S**** +****η, GeV**

**Combinations/25 MeV**

**S/****√****B = 5 ****σ**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of DSη(2640): confirmation from IHEP analysis

**IHEP group using standard SOAP with Photon calibration tables provided by ITEP reproduced general features of the ****D****S****η**** peak. **
**These tables are available upon request.**
**Working on details ...**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of DSη(2640): η   3π/ η     γ γMonte-Carlo study

**Generated 10000 events:**
**                   ****Reconstructed Ds        Ds*                Efficiency**
**Dseta(2630)                                (100% Br)**
**eta -> 3pi      609.5 +-37.71     88.35+-15.31     14.5+-2.5 %**
**Dseta(2630)**
**eta -> gg     545.3 +-30.84     187.9+-19.28     34.45+-3.53 %**
**Ds(2112)      712.1 +-35.87     206.7+-27.73     28.97+-3.89 %**
**Dspi0 (2317)  712.1 +-35.87     180.1+-28.0     25.3+-3.93 %**
**Reconstructed in the experiment:  Ds 732.7 +- 37.74**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of DSη(2640): η   3π/ η     γ γMonte-Carlo study

**D****S****η   3π/D****S**** η     ****γ γ (Monte-Carlo)****D****S****η   3π/D****S**** η     ****γ (Experiment)**

**= .92 +-.46**

**About 60% of ****D****S  ****are coming from D****S**** η**
**according Monte-Carlo****: too much??**

- SELEX meeting 08/06/03

- presented by M. Kubantsev

## Study of  DS+η: work in progress

**Strong indication of a new Ds family state, **
**    ****BUT much work to do:**
**Reflections and backgrounds**
**Event by event comparisons**
**Theory speculations: hybrid gluon-quark states, radial center mass excitations?**
**Any suggestions?**

- SELEX meeting 08/06/03

- presented by M. Kubantsev