Download R measurement and QCD study in the full BEPCII energy region

R-QCD Programme at BESIII
Guangshun Huang
University of Science and Technology of China (USTC)
BESIII R-QCD Workshop
Aug.16, 2016, Liaoning Normal U., Dalian
Outline
 BESIII R-QCD overview;
 Precision measurement of R value;
 Versatile QCD studies;
 Summary
Aug.16, 2016, Dalian
G.S. Huang: R-QCD
2
Physics in BESIII -QCD group
  mass measurement;
 Measurement of R value in 24.6 GeV;
 Study of high mass charmonia in 3.84.6 GeV;
 QCD studies:
–
–
–
–
–
–
–
2016.7.11, Lu An
Measurement of form factors;
Fragmentation function;
Cross section of exclusive processes;
Baryon pair production near threshold;
Initial state radiation;
Phase between electromagnetic and strong interaction;
……
G.S. Huang: 973 tau-QCD
3
R-QCD at BESIII
• Part of the tau-QCD group, one of the five
physics groups at BESIII;
• Major fundings (USTC-IHEP):
Key project of NSFC:
BEPCII/BESIII重粲结构精细扫描和QCD实验研究;
973 project of MOST:
北京谱仪III tau-粲物理实验研究：与QCD物理研究
(also include tau physics).
Aug.16, 2016, Dalian
G.S. Huang: R-QCD
4
Major plans for data taking
6%
Charm
baryons
3.5%
Y(2175)?
Babar
• Phase I: pre-study, 8 days (2012)
to extend?
❶ Machine study at 2.0, 2.5 and 4.2(4.6) GeV, MC tuning, …
• Phase II: scan continuum region, 4 months (2015)
❸ 15 points in 2.03.6 GeV, step 100 MeV, 100k+ hadrons<3 GeV.
•Phase III: scan resonance region, 1.5 months (2013-2014)
❷ 100 points in 3.84.6 GeV, 100k events, step 2, 5,10, 20 MeV.
Single/separated beam for beam associated background study.
Aug.16, 2016, Dalian
G.S. Huang: R-QCD
5
Scan data for R-QCD studies
• 800 pb-1 in 2.0 – 3.671 GeV;
• For proton, neutron, hyperons, and mesons.
7 Apr. 2016, Mainz
G.S. Huang: Timelike Form factors @BESIII
6
R Scan in 3.8 - 4.6 GeV
• Data taken 2013.12.9 - 2014.1.24;
• 104 energy points in total, 800 pb-1;
• >100k hadronic events each points.
Nov.12, 2014, CERN
7
Data sets for R-QCD Studies
 2012 test run: 4 points at low energies;
 2013-2014 scan: 104 points >3.8GeV, 800 pb-1;
 2014-2015 scan: 20 points in 2-3 GeV, 525 pb-1.
 + data at continuum from various projects;
 + (3770), XYZ data (for ISR studies).
 For more practical information, please visit,
http://docbes3.ihep.ac.cn/~tauqcdgroup/
 R-QCD Group meeting: 3 PM Wednesday.
Aug.16, 2016, Dalian
G.S. Huang: R-QCD
8
Work distributions
Discussed between QCD and LH groups
2015.1.28
• R measurement: USTC + IHEP + JGU
• Baryon form factors
–
–
–
–
–
ppbar: Xiaorong, Lei, Cristina, Dexu, Christoph, Alaa, Yadi
nnbar: Paul, Alaa, Xiaorong, Samer, Yadi
Lambda form factor: Cui, Karin
Lambda Sigmabar0: Cui, Joachim, Karin
Sigma Sigmabar: Cui, Walter, Karin
All baryon pairs: Qinglei(LH)
• Baryon threshold studies
–
–
–
–
Lambda-pair: Xiaorong, Liang
Lambda Sigmabar0: Xiaorong
Sigma Sigmabar: Liang, Xin
Xi Xibar: Lei, Zhen
• Baryon excited states
Aug.16, 2016, Dalian
G.S. Huang: R-QCD
9
Work distributions
Discussed between QCD and LH groups
2015.1.28
• Y(2175) related
–
–
–
–
–
–
–
–
–
phi pi+ pi-: Zhihong; Fang Liu(LH)
phi pi0 pi0: Yateng; Xiaolin Kang(LH)
New decays: Huanhuan Liu(LH)
h1 pi pi:
h1(KKpi0) eta: Peilian Li
rho eta: Zhe, Magnus
phi eta: Xinlei, Magnus
(pi+ pi-) recoil: Xinlei, Xiaorong
(pi0 pi0) recoil: Yateng
• Multi-hadron
–
–
–
–
ee -> 4pi (pi0): Haiming
ee -> K K pi pi (pi0):
Inclusive hadron: Xinlei, Zhe, Benedikt, Andreas; Peilian Liu(LH)
Momentum distribution:
• Beyond Standard Model
– ee -> eta_c: Joachim, Andrzej
Aug.16, 2016, Dalian
G.S. Huang: R-QCD
10
e-
Definition of R:
• At lowest order
s
+
e
e-
Rº
q-
hadrons
lowest
order
q
m-
s
e+
• At higher order
= SQf2
flavor
color
m+
Number of quark colors
• R is one of the most fundamental quantities in particle
physics that directly reflect the flavor and color of quarks.
• Directly test quark model & QCD, and discover new particles.
Aug.16, 2016, Dalian
G.S. Huang: R-QCD
11
Measurement of R Values
R
1

N had  N bg
s m  m  L   had  (1   )
Our goal:
3% precision
Nhad: observed hadronic events
Nbg: background events
L:
integrated luminosity
had: detection efficiency for Nhad
:
radiative correction factor
smm: can be precisely calculated(QED). Measurement of R
is to measure the total s(e+e-→hadrons)
Except for controlling each item to the precision requested,
stable long term machine and detector performance is crucial.
Aug.16, 2016, Dalian
G.S. Huang: R-QCD
12
Our expectation from the test run
• Publications:
–
–
–
–
Proton form factor, drafting
Lambda threshold, in review
Inclusive hadron production, ongoing
R value, still long way to go?
• R measurement:
–
–
–
–
LundARLW tuning;
New generator (Ronggang);
Hadronic event selection;
Luminosity determination.
All have to be finished!
• The time windows is  10 months!
Aug.16, 2016, Dalian
G.S. Huang: R-QCD
13
Our expectation from the test run
• Publications:
–
–
–
–
–
Proton form factor, published
Lambda threshold, preliminary
Luminosity determination, draft
Inclusive hadron production, presented
R value in continuum, presented
• More works:
– LundARLW tuning;
– Pythia?
– Hadronic event selection.
• We have to release the R values as soon as possible!
Aug.16, 2016, Dalian
G.S. Huang: R-QCD
14
Status: analyses with test run data
• Publications:
–
–
–
–
–
–
Proton form factor, published in 2015
(LundARLW + Exclusives) tuning, submitted to CPC
Lambda threshold, CWR since May 12
Luminosity determination, with Spokes Mar.21, May 4
Inclusive hadron production, still ongoing
R value in continuum, with conveners since Apr.8
• More works:
– LundARLW tuning, stalled for long, restarting
– Pythia? No plan
– Cross check using Phokhara, with JGU group
• I have to say our efficiency is too, too low!
Aug.16, 2016, Dalian
G.S. Huang: R-QCD
15
R values in the continuum region
Based on 2012 test run + other continuum data.
Aug.16, 2016, Dalian
G.S. Huang: R-QCD
16
R Scan in 3.8 - 4.6 GeV
• Data taken 2013.12.9 - 2014.1.24;
• 104 energy points in total;
• >100k hadronic events each points.
Aug.16, 2016, Dalian
G.S. Huang: R-QCD
17
QCD studies
  at threshold, Xiaorong Zhou, CWR for 3 months











cc near threshold, Weiping Wang, with referees
e+e-K+K-, by Dong Liu, with referees
J/ resonance parameters, by Xingyu Zhou, with conveners
e+e-/0, , by Zhe Zeng, memo almost ready
e+e-p𝑝, by Lei Xia, memo almost ready
e+e-K+K-, by Zhihong WangYankun Sun, finalizing memo
Inclusive 0/Ks, e+e-, by Xinlei Gao, ongoing
Energy calibration for R scan, by Dong Liu, ongoing
e+e-+-, by Zhihong Wang  Yaxing Tan, restarting
e+e-00, by Yateng Zhang, no progress
e+e-n𝑛, by Xiaorong Zhou, no progress
Aug.16, 2016, Dalian
G.S. Huang: R-QCD
18
Summary
• Data for R-QCD studies has been there
for us to explore;
• Our visibility was very good around 2015
data taking, but then diminished;
• Quite a few analyses ongoing, but overall
the progresses are very slow;
• The situation must be improved!
• 形势严峻、压力巨大！
Aug.16, 2016, Dalian
G.S. Huang: R-QCD
19