BESIII Ds 2015 BESIII December 17 2015 Outline

BESIII Ds 物理研究 董燎原 2015 年BESIII 粲介(重)子物理研讨会 December 17, 2015

Outline • • • Data samples at BESIII Current results from Ds decays Key physics topics in Ds decays Preparation for Ds data taking Summary

Data samples at BESIII： Data @ 4170 for Ds physics: CLEO-c has 600 pb-1 data @ 4170 Me. V. 3

Which energy: 4170 Me. V or 4010 Me. V ? CLEOc PRD 80, 072001 (2009) In order to find a favorable point, CLEO-c performed a energy scan: CLEO-c ran at the 4170 Me. V and accumulated 600 pb-1 data. Many world-class results for Ds decays from CLEO-c have been published. 4. 01 Ge. V 4. 17 Ge. V 4

Current Results from Ds decays based on the data sample at Ecm=4. 01 Ge. V (482 pb-1) 1. BF(Ds+ → η’X) and BF(Ds+ → η’ρ+) Published in PLB 750, 466 (2015) This is the BESIII Ds paper ! 2. BF(Ds+ → l νμ) and f. Ds BESIII Spokespersons review stage 3. BF(Ds+ → ηe+νe ) and BF(Ds+ → η’e+νe) BESIII Spokespersons review stage

BF(Ds+ → η’X) Double Tag method: Fit to 2 D: M(ηπ+π-) vs MBC Signal = 68 ± 14 events BF(Ds+ → η’ρ+) Single Tag method: Fit to 2 D: cosθ_helicity vs MBC Ds → η’ρ+ = 68 ± 14 events Ds → η’π+π0 = -13 ± 56 events

BF(Ds+ → l νμ) and f. Ds BF(Ds+ → ηe+νe ) and BF(Ds + → η’e+νe ) Branching fractions are statistics-limited.

Key Physics topics in Ds Decays • • • Pure Leptonic Decays and decay constant f. Ds Semileptonic decays and form factors Hadronic decays Baryonic decays Dalitz Plot and Amplitude analyses Rare and forbidden decays MC results are from “A proposal to study Ds decays at Ecm=4170 Me. V” (Doc. DB=129, June 2014) For a review of the Ds physics, please find it in Part Five of “Physics at BESIII” (ar. Xiv: 0809: 1869, Mod. Phys. A 24 (sup). 1 (2009)) 12

Pure leptonic Decays Experimental/throretical status: ar. Xiv: 1509. 02220 prepared for PDG 2016 World average f. Ds = 257. 8 ± 4. 1 Me. V, LQCD = 249. 1 ± 1. 1 Me. V ~2. 0σ difference between two! - CLEOc results have comparable accuracy to those from B-factories. - The CLEOc results are all statistically limited (their syst. ~ 3%) - With 3/fb, our projected statistical uncertainty would be ~3%! - Our results will contribute to the world’s |Vcs| determination. 13

Ds→μν Branching fraction CLEO-c (600 pb-1) PRD 79, 052001(2009) Statistical uncertainty = 6. 3% BESIII MC (3. 0 fb-1) Expected to be the best measurement Statistical uncertainty = 3. 0% Belle (931 fb-1) JHEP 09(2013)139 Statistical uncertainty = 5. 3% 14

Ds semi-leptonic Decays CLEOc (600 pb-1) PRD 80, 052009(2009) Still very statistics-limited. BESIII MC (3. 0 fb-1) statistical uncertainty = 8. 1% statistical uncertainty = 4. 0% 15

Hadronic Ds Decays Absolute Ds hadronic branching fractions significantly impact the precision of some important measurements: - Understanding the Ds decays is important. For instance, BF(Bs→Ds X) is very large. - Just like D 0 → K-π+, Ds+ → K-K+π+is often used as a “normalization” mode. Experimental status for BF(Ds+ → K-K+π+) : 16

BESIII MC (3. 0 fb-1) We can get very clean Double tagged samples!

Baryonic decays This decay is quite interesting because the flavors of the all valence quarks that constitute the initial state. CLEOc made the first measurement based on their 4170 data (325 pb-1 )data. CLEOc (325 pb-1@4170) PRL 100, 181802(2008) BESIII MC (3. 0 fb-1) Signal yield 13. 0 ± 3. 6 events; No background This is ± 28% (± 12%) for statistical(systematic) uncertainty. Statistical uncertainty ~15% Increased statistics is the key to improvement! 18

Dalitz plot and Amplitude analyses Rare and forbidden decays The rare and forbidden semi-leptonic decays of Ds meson provide an ideal lab for searching for new physics: 19

Preparation for Ds data taking 1. Is Dtag ready ? 2. Is MC production ready ? 3. Preliminary analysis list

Is Dtag ready to reconstruct Ds ? Yes, it is ready. With the default setup in BOSS 6. 6. 4. p 02, We can reconstruct all the hadronic modes shown in latest CLEOc paper (PRD 88, 090001(2014))

Is MC production ready? Data: Yes, we already have data (the R-scan data). Ecm = 4. 17 Ge. V, runs 34447 -34460 (14 runs) 18/pb MC: Yes, we have generated 10 x MC samples. Will do tagging and systematic studies based on this sample.

Preliminary analysis list

Summary With 3. 0 fb-1 of data at ECM = 4170 Me. V, BESIII will be able to improve on the already world-class results from CLEO-c and also make many new measurements ! Thank you !