1. Oleg Samoylov (JINR, Dubna) @ AYSS’12 conf., Feb. 6-11, 2012
Precise measurement of Charm Dimuon production cross-section in νN interactions and its various applications
Oleg Samoylov (JINR, AYSS’12 conf., Feb. 6-11, 2012

2. Motivation of the Charm Dimuons
Charge current (CC)
Neutral current (NC)
qu (ν)
qd (ℓ) f f' g
g / Cos θW W+ Z0
NuTeV analysis
Sin2θW = 1 − MW2/MZ2 = ± (stat.) ± (syst.)
Rν = σνNC / σνCC = ± (SM )
Rν = σνNC / σνCC = ± (SM )
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

3. Motivation of the Charm Dimuons
NuTeV
for the NOMAD
Roberto Petti
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

4. A direct probe of the Strange sea
Proton structure is defined by
Parton Distribution Functions (PDF’s)
of quarks q(x) and gluons g(x)
νµN → µ−µ+ X
νµs → µ−c → µ−µ+ X
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

5. Available charm dimuon data
νµN → µ−µ+ X ⇒ νµs → µ−c → µ−µ+ X
Experiment
Pubication
Charm dimuons
Neutrino Energy, GeV
CDHS
Jun.1982
9 922
(20)
CHARM II
Oct. 1999
3 100
(24)
NOMAD
Jul. 2000
2 714
(27)
NuTeV
Feb. 2001
5 102
(157.8)
CCFR
5 030
(150)
CHORUS
Apr. 2008
8 910
(27)
Strange sea PDF s(x) based on approx events only
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

6. Neutrino induced charm dimuons
ν-induced charm dimuon production
Dc = Σ fh Dch,
Bμ = Σ fh B (h → μ+ X),
h = D0, D+, Ds+, Λ+
Charm production in (anti)neutrino DIS provides
a clean and direct access to s(x)
|Vcs|2=0.95
|Vcs|2=0.05
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

7. NOMAD experiment at CERN SPS
Front Calorimeter (FCAL)
Muon neutrino beam
NIM A 515 (2003)
Drift Chambers (DCH)
NIM A 404 (1998)
1. Largest samples of neutrino interactions currently available:
- 20 M events with Iron in Front Calorimeter (50 k dimuons)
- 2.5 M events with Carbon in Drift Chambers
2. Resolution for the vertexes:
in Drift Chambers 0.1 ÷ 0.25 cm and in Front Calorimeter 0.6 ÷ 1.0 cm
3. Excellent reconstruction quality of individual (charged) tracks ∆p/p=3.5%, ε=95%
4. Good calorimetry: for ECAL ∆E/E=3.2%/E[GeV], for FCAL and HCAL ∆E/E=104%/E[GeV]
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

8. Reconstruction of the dimuon events
Eν = Eµ− + Eµ+ + Ehad
Event information
Eν = 81.4 GeV
Eµ− = 32.6 GeV
Eµ+ = 19.0 GeV
Mµµ = GeV
Q2 = 3.26 GeV2
W2 = 89.4 GeV2
Background
Signature
Stat.
Eff., %
νμ CC
65.8
μ-μ+
20 480
22.5
μ-μ-
7 150
Charm dimuon
Charm dimuon exp. DATA and Bg. subtraction:
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

9. Relevance of the NOMAD dimuon data
νµN → µ−µ+ X ⇒ νµs → µ−c → µ−µ+ X
Experiment
Pubication
Charm dimuons
Neutrino Energy, GeV
CDHS
Jun.1982
9 922
(20)
CHARM II
Oct. 1999
3 100
(24)
NOMAD
Jul. 2000
2 714
(27)
NuTeV
Feb. 2001
5 102
(157.8)
CCFR
5 030
(150)
CHORUS
Apr. 2008
8 910
(27)
2011
15 340
6-300 (27)
The NOMAD has the largest sample of ν-induced charm dimuons
The neutrino energies closest to the charm production threshold
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

10. Charm dimuon X-section measurement
Measure RATIO of cross-sections to reduce systematics
Rµµ ≡ σµµ /σcc ≃ Nµµ /Ncc (x); x = Eν , xBj , √s
Require leading µ− and Q2 ≥ 1 GeV2
∫ σµµ φ dx dy dEν = 5.15 ± 0.05 × 10−3 νµ CC
Total systematic uncertainty (17 different sources) ~ 2%
Agreement with model calculation based upon global PDF fit with NuTeV+CCFR dimuon data only
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

11. Sensitivity to the Strange sea
Add NOMAD σµµ /σcc to global PDF fit with NuTeV and CCFR dimuon data
S. Alekhin, R.Petti
Consistency of central values
Reduction of s(x) uncertainty by a factor 2 down to 3%
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

12. Strange sea and c-quark parameters
Charm quark mass and strange sea supression factor
Experiments
mc (mc), GeV κs
E531 + NuTeV + CCFR
1.010 ±0.095
0.62 ±0.005
E531 + NOMAD
1.058 ±0.059
0.63 ±0.004
E531 + NuTeV + CCFR + NOMAD
1.070 ±0.067
0.61 ±0.002
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

13. Strange sea and c-quark parameters
Charm fragmentation D(z, ε) in Collins-Spiller parametrization
Experiments ε
E531
0.169 ±0.036
NOMAD /
E531 + NOMAD
0.165 ±0.025
Semileptonic branching ratio Bµ(Eν) = a/(1 + b/Eν)
Experiments a
b, GeV
E531
0.094 ±0.010
6.6 ±3.9
E531 + NuTeV + CCFR
0.086 ±0.006
4.1 ±2.5
E531 + NOMAD
0.094 ±0.004
6.0 ±1.6
E531 + NuTeV + CCFR + NOMAD
0.094 ±0.003
5.6 ±1.4
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

14. Quark fragmentation measurement Scheme
F = ED ⇒ D = E-1F
Fπ = (Fee±,
Fℓp+,Fℓn+,Fℓp-,Fℓn-,
Fνp+,Fνn+,Fνp-,Fνn-,Fνp+,Fνn+,Fνp-,Fνn-)
Dπ = (Dd+,Du+,Ds+,Dc+,
Mp,d+,Mp,d-,Mp,u+,Mp,u-,Mp,d+,Mp,d-,Mp,u+,Mp,u-,Mp,s-)
F, E, D ( z,pT ; { s | x,Q2 } )
NOMAD
Durham HepData
(more than 100 experimental DATA)
See talk by Svetlana Starikova
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

15. Current JINR activity at CERN
More precise knowledge of the Strange sea of the Nucleon allows to make more accurate prediction of strange particles production in pp collisions (ATLAS, CMS)
Measurement of fragmentation functions Dq and Mp,q provides better estimation of spin transfer from quark to produced particles (COMPASS)
Improvement of neutrino-induced charm dimuon production can reduce uncertainty of charm background prediction for νμ → ντ oscillation experiments approx. by a factor 2 (OPERA)
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

16. Muon neutrino from Atmospheric charm
The Baikal experiment is interesting in prediction for cross-sections of charm particle productions in atmospheric nuclear cascade with generation of the muonic neutrino.
In collaboration with N.Budnev and S.Sinegovsky from ISU and API (Irkutsk) we plan to calculate neutrino flux prediction for different zenith angles using parameterization of the spectrum of primary cosmic rays in wide energy interval (including ``knee'' region).
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

17. Publications in 2011 and Acknowledgements
O.Samoylov, R.Petti, PEPAN Lett., 2011, Vol.8, №7 (170) Pp
A.Edemskaya, D.Naumov, O.Samoylov, PEPAN Lett., 2011, Vol.8, №7 (170) Pp
O.Samoylov, Proceedings of the PANIC-11 conf., 2011, MIT (Cambridge, USA)
O.Samoylov, Proceedings of the AYSS’11 conf., 2011, JINR (Dubna, Russia) Pp.114
Work has been done in collaboration with R.Petti (USC) and D.Naumov (JINR), with participation of M.Gonchar (JINR), A.Edemskaya (ISU), S.Starikova (ISU). We are grateful to V.Cavasinni, L.Camilleri, L.DiLella for stimulating discussions of this work.
This work is partially supported by JINR grant, CERN, RFBR grant, RF Targeted Program “Research and Research-Human Resources for Innovating Russia”.
Charm dimuons in NOMAD
Oleg Samoylov (JINR)

18. Oleg Samoylov (JINR, Dubna) @ AYSS’12 conf., Feb. 6-11, 2012
Precise measurement of Charm Dimuon production cross-section in νN interactions and its various applications
Oleg Samoylov (JINR, AYSS’12 conf., Feb. 6-11, 2012