Open Charm Cross Section Measurement at 4 260

Open Charm Cross Section Measurement at 4. 260 Ge. V Zhen Gao University of Science and Technology of China

Data Set • Data: 825. 7 pb-1@4. 260 Ge. V • MC: KKMC for D 0: D 0 D 0 bar , D 0*D 0*bar , D*D π , D*D* π , D+*D- (D+* --> D 0 π+), D+*D*KKMC for D±: D+D- , D+*D*- , D*Dπ (D+*-> π0/γ + D+), D*D*π KKMC for Ds±: Ds+Ds- , Ds+*Ds-* Inclusive MC at 4260 ** For example D 0 D 0 bar D 0 ->K-π+ and D 0 bar -> anything (50%) D 0 bar->K+π- and D 0 -> anything (50%)

Method (take D 0 as an example) 1. Get D 0/D 0 bar signal by tagging D 0/D 0 bar with Kπ mode. (D 0/D 0 bar + anything) + sideband 2. Get all the possible exclusive D 0/D 0 bar channels with MC. 3. Fit all the D 0(D 0 bar) channels together with sideband. Why not fit the recoil mass of each exclusive D 0(D 0 bar) channels? The statistical quantity for R scan data is not enough; Wrong combination while tagging D 0*

Dtag • Using Dtag. Tool: tag a D 0 with D 0 ->kpi mode (branching fraction: 3. 89%) • Signal region: |M-M(D 0)| < 15 Me. V Sideband region : 25 Me. V<|M-M(D 0)|<55 Me. V

Compare M(KPI) from Data and MC

p. D 0 and p. D 0 bar p. D 0: + p. D 0 bar: =

p. D 0 at 4. 260 Ge. V Bhabha Inclusive_DD Inclusive_qqbar Inclusive_had Dimu

In the low momentum region Angle between K and π in D 0 P(K)-P(π) in D 0 The events in the low momentum region may come from cosmic-ray !

Whether D(*)π exist? • Tag D 0 with Kπ mode • Tag D 0* with π0+D 0 • At least one π+ or π- from other tracks (not from D 0) • Mass of X in D 0(*) π(±) + X while the momentum of D 0 is less than 0. 5 Ge. V (D 0 is not from D 0(*))

Recoil mass Recoil(D 0 π+) Recoil(D 0* π+) Recoil(D 0 bar π) Recoil(D 0*bar π)

Conclusion • For multi-body processes(D(*)π) , DDπ signal is not obvious (does not exist or the cross section is very low) , but the D*Dπ and D*D* π signals are very clear. • Is there any other multi-body precesses? Such as D(*)ππ ?

Fitting Result MC can not describe data well? Any other components do not include?

Result of Ds+ and D+

Primary Cross section(1) Channel Number ε 1+δ Br. σ Ds. Ds 783± 120 0. 418 0. 846 0. 055 24. 4± 3. 74 Ds*Ds 1133± 215 0. 429 0. 847 0. 055 34. 3± 6. 5 Ds*Ds* 18393± 215 0. 442 0. 847 0. 055 540. 9± 6. 3 Channel Number ε 1+δ Br. σ D+D- 5509± 114 0. 496 0. 846 0. 095 83. 7± 1. 73 D+*D- 37030± 263 0. 503 0. 846 0. 095 • (1 -0. 677) 1717± 12 D+*D-* 7379± 185 0. 507 0. 846 0. 095 • (1 -0. 677) 340± 8. 2 DD*π 21016± 461 0. 510 0. 846 0. 095 • (1 -0. 677) 961. 2± 21 D*D*π 4597± 229 0. 488 0. 846 0. 095 • (1 -0. 677) 219. 7± 11

Primary Cross section(2) Channel Number ε 1+δ Br. σ D 0 D 0 bar 2438± 85 0. 551 0. 846 0. 039 81. 2± 2. 8 D 0*D 0 bar 22793± 274 0. 565 0. 846 0. 039 740. 4± 8. 9 D 0*bar 16138± 645 0. 584 0. 847 0. 039 1013. 1± 40 D*Dπ 30266± 412 0. 484 0. 846 0. 039 1147. 6± 15. 6 D*D*π 7165± 252 0. 520 0. 846 0. 039 252. 9± 8. 9