# Presentation: 845451

## Recent Charm Production and Neutrino Oscillation Results From CHORUS 

**Aysel Kay****ış**** Topaksu,**
** ****University of ****Çukurova****, Adana**

**PANIC05****, ****Santa Fe****,****NM**** ****24**** – ****28**** ****October****  2005**

## Outline

- Result on oscillation
- Conclusion

- CERN Neutrino Beam Line
- CHORUS detector and Automatic emulsion data acquisition
- Results on charm analysis

- Measurement of total D0 production
- Anti-neutrino charm production
- Measurement of fragmentation properties of charm
*Bμ : muonic branching ratio*
- Measurement of D*+ production
- Search for Superfragment and Hyperfragment

## Neutrino beam

- Wide Band Beam
- 5.06  1019  POTs (1994-1997)
- <E>  ~  27 GeV
- <L>  ~  0.6 km
- Prompt ********  :  negligible

- West Area Neutrino Facility at CERN SPS

- CHORUS, NOMAD

- 450 GeV

- <L>/<E>  ~  2  10-2  km/GeV

-  m2 > 1 eV2

## CHORUS detector

**Active target**
- nuclear emulsion target (770kg)
-   scintillating fiber tracker

**Muon spectrometer**
- p/p* *= 10 – 15%
-         (p < 70 GeV/c)

**Calorimeter**
- E/E = 32 %/ E (hadrons)
-            = 14 %/ E (electrons)
- h= 60 mrad @ 10 GeV

**Air-core magnet**
- p/p = 0.035 p* *(GeV/c)  0.22

**CHORUS detector**

- Veto

- 

- ~ 27 GeV

**CERN SPS**

## Automatic emulsion data acquisition

- 1

- 2

- 3

- Angular acceptance : 400 mrad

- Track segments from 8 plates overlapped

- At least 2-segment connected tracks

- Eliminate passing through tracks

- Reconstruct full vertex topology

- Volume : 1.5 x 1.5 mm2 x 6.3 mm

- 1

- 2

**Location of ******** interaction vertex guided by electronic detector.**

**Full data taking around ******** interaction vertex called Netscan**

**Offline tracking and vertex reconstruction**

- ~ 11 minutes / event

## Measurement of D0 production

***                                               ******Phys. Lett. B 527 (2002) 173,  based on *****~25% of statistics**
-                                        *Phys. Lett. B 613 (2005) 105,  based on full statistics*
**NOW****: ****full sample: ~ ****95000**** CC events**

**Candidate selection**

- Primary track matched to detector muon
- Daughter track matched to detector track
- 3 ~ 13 μm <  I.P.  wrt. 1ry vtx  < 400 μm

-  2 prong (V2)     819

-  4 prong (V4)    226

**Confirmed D****0****sample  **

**Selection efficiencies**

-  V4  :  0.754 ± 0.027

-  V2  :  0.561 ± 0.018

**(D****0****      V4 ) / ( D****0****     V2)**
**    ****= 0.207 ± 0.016 ±0.004**

## Fully neutral D0 decay mode:

**σ(D****0****)/σ(CC) = ****(****2.69 ± 0.18 x 0.13****)%**

- Fully neutral D0 decay mode:

- BR4/BR2 – measured
- BR4 = 0.1338 ± 0.0058                        **PDG**
- BR(D**0**         neutrals) = 1-BR4 x(1+ BR2/BR4 ) = 21.8 ± 4.9 ±3.6% (6 prong negligible)

- Total production cross section:

- Relative detection efficiency D**0**/CC = 0.88

##  Charm production in antineutrino interactions

**N********+**** = 2704**
**N********-**** ~ 95000**
**Selected events for visual insp= 81**
**found charm = 40**

- “1 spectrometer events”

- kink> 50 mrad, F.L > 50 m

**Phys. Lett. B 604 (2004) 11-21  **

**= ****4975 ± 187 ±53**

-  **±0.****7) %**

## Charm production rate as a function of neutrino energy

## Measurement of fragmentation properties of charm

**Measurement of fragmentation properties of charm**

**Measurement of D****0**** momentum **

**Inverse of **
**geometrical **
**mean of opening angle of daughters**

**D Momentum**

## Z-distribution

**Z-distribution**

- Fits to Collins-Spiller and Peterson:

- Also an E531 measurement
- Indirect measurements from dimuon data:
- CDHS, CCFR, CHARMII, NuTeV, CHORUS

- CHORUS:
- Fit to Peterson formula
- (dotted curve is MC model)

- z=ED/ 

## Most charmed particles are produced in the forward region

**Feynman x (***x**F***) -distribution**

- xF=pL/pmax

- _Phys. Lett. B__604__ (200__4__) 1__4__5_

## Bμ : muonic branching ratio 

- B = 7.3  0.8  0.2%

- Taking into account the new  CHORUS measurement of
- Br (D0  V0)

-     B = (8.5 **** 0.9 **** 0.6)%

- Dimuon events have larger visible energy
- Evis > 30 GeV

- Bμ |Vcd|2LO=(0.474  0.027)x10-2
- CDHS, CHARM II & CCFR averaged

- |Vcd|LO= 0.2390.046

*0.221< |V**cd**|<0.227 at 90% CL *
*using CKM **unitarity** and  3 generations*

*Direct observation of the charm parent and its muon decay*

*Phys. Lett. B626 2005,24-34 *

## The results takes into account the new 

**CHORUS measurement of B(****D0 ******** ****V0)********22% **

## Measurement of D*+ production

- Search for D*+ in the decay channel: D*+  D0  +

- 

- μ-

- D0 fl>100mm

- +

- K-

- +

- 0.4 <p(+)<4 GeV/c
- 10< pT<50  MeV/c

- Background prediction

- (1)Shape of  signal & background
-  normalized to the observed events
- (2-3-4) shape normalized to the total number of D0 and C+ respectively

- D*+ signal in the D0 h+ sample

- No signal in the D0h- sample

- No signal in the C+h- sample

- No signal in the C+h+ sample

- 

- μ-
- -

- D0

- +

- D*+

- Measurement of D*+ production

- _Phys. Lett. B614 (2005) 155_

## Measurement of D*+ production 

-  *Br(D***+** **** D**0** *+)*=0.677±0.005 (PDG)*

- assuming that _prompt_ D*+ and D*0 production rates are equal we get

- NOMAD   0.79 ± 0.17 ± 0.10
-  BEBC        1.22 ± 0.25 %
- Tevatron    5.6 ± 1.8 % (higher energy)

## Search for Superfragments and Hyperfragments

## Typical Candidate Event

- A total of 28 non-mesic
- hyperfragments were
- found

## Results

- (2.0±0.4(stat) ±0.3(syst))x10-3

**Results**

- Superfragment production limit /CC

- < 1.9 x 10-4       (90%C.L.)

- Using the Lambda_c production ratio

-            (σ(c) /σ(CC)= (1.54  0.35(stat)  0.18 (syst))  10-2)

- <     1.3 x 10-2

- (90%C.L.)

*Nuclear Physics B718, 2005, 35-54*

## Oscillation Analysis

-  **Decay mode considered**
**	****i)-************************************************ii)- ****************h****-****(n********0****)************, iii)- **************** 3h****-****(n********0****)************ ****  **
** ****Pre-selection (data from electronic detector)**
**	****-vertex predicted in the emulsion**
**	****-At least one negative track**
**	****	****-1******** sample**
**	****	****-0******** sample**
**Emulsion Scanning**
**	****-Scan back of selected tracks CS********SS********bulk********vertex plate**
**	****-Vertex reconstruction & decay Search, ****NETSCAN**
**	****-Event selection**
**	****-Eye-Scan Check, visible recoil, blob or Auger electron**
**Final kinematical cuts**
**	****-decay length, kink angle, P****t**** at vertex**

## Backgrounds

******-********-********************  ****(****C1)**
**Charm mesons**** in ************************ and ********e**** CC interactions**
**********/e**** N ****→****D****-**** ********+****/e****+ ****X**
**                      ********-****/h****-**** + neutrals****  ~10****-6****/ N********= 0.11**
******-********h****-****(nh****0****)************ ****(****C1)****,**
******-********h****+****h****-****h****-****(nh****0****)************ ****(C3)**
**Charm production similar to ******** channel **
**White interactions**

**1******

**0******

## White kink background

-  Pt[GeV]

- WK

-  h

- WK

-  h

- kink [rad]

**1-prong nuclear interaction with no ionising activity at the interaction point**** ****(fake ********decay topology)**
** ****CHORUS measured :**
-                 ******WK****(****P****T ****> 250 MeV/c) = 24.0**** ± ****8.5 m**

**Post-scanning WK rejection for C3**

******t**** ****cut and ****c******** cut**

## Limit computation  

**Limit ****computation**** **** **

## Limit computation  

**Limit ****computation**** **** **

****** ****number of detectable ************ events if the oscillation probability is = 1**

**N********max**

**0********C1**

**bg**

**data**

**0********C3**

**1********C1**

**51.5****±****9.7**

**59**

**9,447**

**51****±****12**

**48**

**4,974**

**0.100****±****0.025**

**0**

**5,014**

***Feldman and Cousins unified approach***
***G.J. Feldman and R.D. Cousins***
***Phys.Rev. D57 (1998) 3873***

**0********C1**

**0.****3****00****±****0.0****75**

**0**

**5,****26**

**Phase I**

**Phase II**

## Status of oscillation into 

- with sin22*** *> 3.4x10−4 (at 90% CL) at high  m2.

- Status of oscillation into 

**P ******** < 1.****72****x10****-4 ****@ 90% CL**
**S ******** : 2.5x10****-4 **** @ 90% CL**
**P(≤L)= ****28****%**

## Conclusion

- CHORUS still working on charm analysis.
- Measurement of associated charm production in neutral- and
-   charged-current neutrino int.
-  Measurement of the x-distributions of charmed particle
-   production in neutrino interactions
-  Measurement of Lambda_c production and decay into Sigma+
-    in neutrino interactions
- Measurement of diffractive production of D_s in neutrino interactions
- ..............    **Are still in progress**