Physics at bes
Download
1 / 58

Physics at BES - PowerPoint PPT Presentation


  • 120 Views
  • Uploaded on
  • Presentation posted in: General

Physics at BES. Shan JIN (for the BESIII Collaboration) Institute of High Energy Physics (IHEP) jins@mail.ihep.ac.cn USTRON09, Poland September 12-16, 2009. Outline. Introduction of BES experiments and Physics at BES Highlights at BESII Status of BESIII and preliminary results

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha

Download Presentation

Physics at BES

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Physics at bes
Physics at BES

Shan JIN

(for the BESIII Collaboration)

Institute of High Energy Physics (IHEP)

jins@mail.ihep.ac.cn

USTRON09, Poland

September 12-16, 2009


Outline
Outline

  • Introduction of BES experiments and Physics at BES

  • Highlights at BESII

  • Status of BESIII and preliminary results

  • Future prospects at BESIII

  • Conclusion


Physics at bes

Beijing Electron Positron Collider (BEPC) at IHEP

Linac

Storage Ring

BESI: 1989-1998

BESII: 1999-2004

L ~ 51030 /cm2s at J/

Ebeam~ 1 – 2.5 GeV

BES

BSRF

BESIII: 2008-

Physics run started in March, 2009. 100M (2S) and 200M J/ events collected

BEPCII: L reached 31032/cm2sat (3770)

designed L: 1033/cm2s

3


Physics at bes

北京正负电子对撞机(BEPC)示意图

储存环的周长为240.4米

注入器长202米

对撞能量2-5GeV

物理目标


Why tau charm physics is interesting
Why tau-charm physics is interesting

in the past

in the era of LHC

in the future

Abundant resonances(J/y family, huge Xsections)

Tau-charm threshold production(in pairs tagging  background free, no fragmentation, kinematic constrains, quantum coherence,…)

Charm quark: A bridge between pQCD and non-pQCD

A ruler for LQCD

J/y decay Gluon rich environment

Flavor physics Complementary to LHC: virtual vs real

A broad spectrum & efficient machine:


What highlight physics interested us
What (highlight) physics interested us

hep-ex/0809.1869

  • Light hadron spectroscopy

    • Full spectra: normal & exotic hadrons QCD

    • How quarks form a hadron ? non-pQCD

  • Charm physics

    • CKM matrix elements  SM and beyond

    • mixing and CPV  SM and beyond

  • Charmonium physics

    • Spectroscopy and transition  pQCD & non-pQCD

    • New states above open charm thresholds  exotic hadrons ?

    • pQCD: rp puzzle  a probe to non-pQCD or ?

  • Tau physics and QCD

    • Precision measurement of the tau mass and R value

  • Search for rare and forbidden decays

Precision test of SM and search for new physics


Light hadron spectroscopy
Light hadron spectroscopy

Glueball spectrum from LQCD

Many results in BESII:

~ 50 publications

Much more from BESIII:

100 statistics,

10 g resolution

  • Motivation:

    • Establish spectrum of light hadrons

    • Search for non-conventional hadrons

    • Understand how hadrons are formed

    • Study chiral symmetry in QCD

  • Why at a tau-charm collider ?

    • Gluon rich

    • Larger phase space than at higher energies

    • Clean environment, JPC filter

Y. Chen et al., PRD 73 (2006) 014516


Physics at bes

Multi-quark State, Glueball and Hybrid

  • Hadrons consist of 2 or 3 quarks:

    Naive Quark Model:

  • New forms of hadrons:

    • Multi-quark states:Number of quarks >= 4

    • Hybrids:qqg,qqqg …

    • Glueballs:gg, ggg …

Meson( qq )

Baryon(q q q)

How quarks/gluons form a hadron is far from being well understood.


Physics at bes

Multi-quark states, glueballs and hybrids have been searched for experimentally for a very long time, but none is established.However, the effort has never been stopped, especially, during the past three years, a lot of surprising experimental evidences showed the existence of hadrons that cannot (easily) be explained in the conventional quark model. Searches for new forms of hadrons are of special importance at BES since J/psi decays are believed as an ideal factory to search and to study exotic hadrons.


Charmonium physics
Charmonium physics for experimentally for a very long time, but none is established.

  • Examples of interesting/long standing issues:

  • rp puzzle

  • Missing states ?

  • Mixing states ?

  • New states above open charm thre.(X,Y,Z,…)

  • What to study ?

    • Production, decays, transition, spectrum

  • For what ?

    • A lab for pQCD and non-pQCD

    • Calibrate LQCD

    • How quarks form a hadron ?

  • Why at a tau-charm collider ?

    • A clean environment

    • Tagging possible

    • Abundantly produced


Highlights at besii
Highlights at BESII for experimentally for a very long time, but none is established.


Physics at bes

BESII for experimentally for a very long time, but none is established.

VC: xy = 100 m TOF: T = 180 ps  counter: r= 3 cm

MDC: xy = 220 m BSC: E/E= 22 % z = 5.5 cm

dE/dx= 8.5 %  = 7.9 mr B field: 0.4 T

p/p=1.7%(1+p2) z = 2.3 cm


Physics at bes

World J/ and (2S) Samples (10 for experimentally for a very long time, but none is established.6)

Largest from BES

J/

(2S)

2002

2001


Physics at bes

Phys. Rev. Lett. 91, 022001 (2003) for experimentally for a very long time, but none is established.

Observation of an anomalous enhancement near the threshold of mass spectrum at BES II

J/ygpp

BES II

acceptance weighted BW

+3 +5

-10 -25

M=1859 MeV/c2

G < 30 MeV/c2 (90% CL)

c2/dof=56/56

0

0.1

0.2

0.3

M(pp)-2mp (GeV)

3-body phase space

acceptance


Physics at bes

Phys. Rev. Lett. 95, 262001 (2005) for experimentally for a very long time, but none is established.

At BESII: Observation of X(1835) in

Statistical Significance 7.7 

BES II

The same origin as ppbar

mass threshold?

 a ppbar bound state?

The +- mass spectrum for  decaying into +- and  


Observation of an anomalous enhancement near the threshold of mass spectrum at bes ii

Phys. Rev. Lett. 93, 112002 (2004) for experimentally for a very long time, but none is established.

Observation of an anomalous enhancement near the threshold of mass spectrum at BES II

BES II

3-body phase space

For a S-wave BW fit: M = 2075 12  5 MeV

Γ = 90  35  9 MeV


Physics at bes

Observation of for experimentally for a very long time, but none is established. mass threshold structure X(1810) in J/   at BESII

BES II

Background

X(1810)

M2(g)

M2(gw)

M()

Jpc favors 0++

Phys. Rev. Lett., 96 (2006) 162002

Possible theoretical interpretations:

glueball, hybrid, multiquark?


Very broad 1 resonance x 1580 observed in k k mass spectrum in j k k 0 at besii
Very broad for experimentally for a very long time, but none is established.1- - resonance X(1580) observed in K+K- mass spectrum in J/ K+K-0 at BESII

BES II

Background

Phys. Rev. Lett. 97 (2006) 142002

So far the only reasonable interpretation is a multiquark state

due to its very broad width


At bes
σ at BES for experimentally for a very long time, but none is established.

  • BES II observed σ in J/  +-.

  • Pole position from PWA:

BES II


At besii
κ for experimentally for a very long time, but none is established. at BESII

  • BESII firmly established neutral  in J/  K*0K  KK in 2006:

  • PWA result

    Pole position:

BES II


Physics at bes

Observation of charged  at BESII for experimentally for a very long time, but none is established.

  • New result: Charged  observed at BESII in

  • Different parameterizations are tried in PWA.

    The pole position:

BESII Preliminary

K*(1410), K*(1430)

consistent with neutral 

M(K0) GeV/c2




Qcd studies at low energies
QCD studies at low energies for experimentally for a very long time, but none is established.

?

BESIII: < 2%

Phys.Lett.B677,(2009)239

  • Understand where exactly pQCD becomes invalid

  • Precision measurement of as running

  • Precision measurement of R

  • input to

  • Related toaQED (s), prediction of higgs mass and g-2

  • A new measurement at BESII on R

    • Precision at ~ 3.5%

    • A new determination of s(s):

      s(M2Z) = 0.1170.012

In good agreement with previous results


Resonance parameter fit
Resonance parameter fit for experimentally for a very long time, but none is established.

Probability =31.8%

Phys. Lett. B660, (2008)315

Heavy charmonia parameters were fitted with the data between 3.7–5.0GeV, taking into accounts the phase angles, interference, energy-dependent width, etc.


Physics at bes

Anomalous for experimentally for a very long time, but none is established.y(3770) lineshape

Black dots: data

Red dots: data subtracting J/y, y(3686) and continuum contribution

Green line: fit with one y(3770) hypothesis;

Red line: fit with two cross section

Blue line: fit with two amplitude

Check all lines !!!

PRL101 (2008) 102004


Status of besiii and preliminary results
Status of BESIII for experimentally for a very long time, but none is established.and preliminary results


Bepc ii storage ring large angle double ring
BEPC II Storage ring for experimentally for a very long time, but none is established.: Large angle, double-ring

RF

SR

RF

Beam energy:

1.0-2 .3GeV

Luminosity:

1×1033 cm-2s-1

Optimum energy:

1.89 GeV

Energy spread:

5.16 ×10-4

No. of bunches:

93

Bunch length:

1.5 cm

Total current:

0.91 A

BESIII detector

IP


Physics at bes

BESIII Commissioning and data taking milestones for experimentally for a very long time, but none is established.

Mar. 2008: first full cosmic-ray event

April 30, 2008: Move the BESIII to IP

July 18, 2008: First e+e- collision event in BESIII

Nov. 2008: ~ 14M y(2S) events collected

April 14, 2009 ~100M y(2S) events collected

May 30, 2009 42 pb-1 at continuum collected

July 28, 2009 ~200M J/y events collected

Peak Lumi. @ Nov. 2008:

1.2 1032cm-2s-1

Peak Lumi. @ May 2009:

3.21032cm-2s-1


Physics at bes

Detector performance and calibration for experimentally for a very long time, but none is established.

●Layer 7

●Layer 22

Wire reso.

Design: 130 mm

dE/dx reso.: 5.80%

Design:6-8%

CsI(Tl) energy reso.

Design: 2.5%@ 1 GeV

Barrel TOF reso.: 78 ps

Design:80-90 ps

Bhabha


E1 transitions inclusive photon spectrum
E1 transitions: inclusive photon spectrum for experimentally for a very long time, but none is established.

c1

c2

co

c1,2 J/

c

BESIII preliminary


Observation of h c e1 tagged y 2s p 0 h c h c gh c
Observation of for experimentally for a very long time, but none is established.hc: E1-tagged y(2S)p0hc,hcghc

background subtracted

BESIII preliminary

BESIII preliminary

N(hc)= 2540±261 c2/d.o.f = 39.5/41.0

Systematic errors under study

CLEO’s results (arXiv 0805.4599v1) :

M(hc)Inc= 3525.35±0.23±0.15 MeV

Br(y’p0hc)×Br(hcghc)Inc =(4.22±0.44±0.52) ×10-4 (G(hc) fixed at G(cc1) ~0.9MeV

CLEOc: Combined E1-photon-tagged spectrum and exclusive analysis

M(hc)avg= 3525.28±0.19±0.12 MeV

Br(y’p0hc)×Br(hcghc)avg =(4.19±0.32±0.45) ×10-4

(arXiv 0805.4599v1)

Select E1-photon to tag hc

A fit of D-Gaussian signal+ sideband bkg. yield:

M(hc)Inc = 3525.16±0.16±0.10 MeV

G(hc)Inc = 0.89±0.57±0.23 MeV (First measurement)

Br(y’p0hc)×Br(hcghc)Inc =(4.69±0.48(stat)) ×10-4 (G(hc) floated)

=(4.69±0.29(stat)) ×10-4 (G(hc) fixed at G(cc1))


Observation of h c inclusive y 2s p 0 h c
Observation of for experimentally for a very long time, but none is established.hc : Inclusive y(2S)p0hc

BESIII preliminary

BESIII preliminary

Inclusive p0 recoil

mass spectrum

background subtracted

Systematic errors under study

Select inclusive p0

A fit of D-Gaussian signal + 4th Poly. bkg yield

N(hc) = 9233±935, c2/d.o.f = 38.8/38.0

Combined inclusive and E1-photon-tagged spectrum

Br(y’p0hc) =(8.42±1.29(stat)) ×10-4 (First measurement)

Br(hcghc) =(55.7±6.3(stat))% (First measurement)

31


Study of 2s 0 0 0
Study of for experimentally for a very long time, but none is established.(2S)→ 00 , ( → ,0 → )

(2S)00

Nc016645±175 Nc24149±82

(2S)

Nc01541±56 Nc2291±23

  • Interesting channels for glueball searches

  • Based on 110M y(2S)

  • BK study from 100M inclusive MC sample and 42pb-1 continuum sample

  • Unbinned Maximum Likelihood fit:

    • Signal: PDF from MC signal

    • Background: 2nd order Poly.

CLEO-c arxiv:0811.0586


Confirmation of the besii observation pp threshold enhancement in j y decays
Confirmation of the BESII observation: for experimentally for a very long time, but none is established.pp threshold enhancement in J/y decays

BES III preliminary

BES II

(2S)→ J/y

0.3

M(pp)-2mp (GeV)

+3 +5

-10 -25

M=1864.6 ± 5.3MeV/c2

G < 33 MeV/c2 (90% CL)

M=1859 MeV/c2

G < 30 MeV/c2 (90% CL)

PRL 91 (2003) 022001


Confirmation of besii observation no pp threshold enhancement in y decays
Confirmation of BESII observation: for experimentally for a very long time, but none is established.No pp threshold enhancement in y’ decays

BES III preliminary

BES II

Mpp(GeV)

No significant narrow enhancement near threshold

(~2 if fitted with X(1860))

No enhancement in y’ decays

In fact, no enhancement in ψ’ ,ϒ(1S) decays and in the process of J/y wppbar show that FSI unlikely .

PRL 99 (2007) 011802


Study of c cj vv v w f
Study of for experimentally for a very long time, but none is established.ccJ VV, V=w,f

  • Backgrounds from sideband & 100M MC events

  • Clear cc1 ff signal

  • to be understood

BESIII preliminary

Test QCD-based theory at ccJ decays

Puzzles for cc0  VV: no helicity suppress

cc1 ff, ww highly suppressed owing to symmetry of identical particles

cc1 fw OZI doubly suppressed


First observation of c c1 wf
First observation of for experimentally for a very long time, but none is established.cc1 wf

BESIII preliminary

Background from sideband & 100M MC events

Clear signal from cc1 w(p+p-p0/rp0)f(K+K-)


Future prospects at besiii
Future prospects at BESIII for experimentally for a very long time, but none is established.


Event statistics at besiii
Event statistics at BESIII for experimentally for a very long time, but none is established.

*CLEO took 10 nb D production cross section while we took 5 nb


Precision measurement of ckm branching rations of charm mesons
Precision measurement of CKM: for experimentally for a very long time, but none is established.Branching rations of charm mesons

  • Vcd /Vcs: Leptonic and semi-leptonic decays

  • Vcb: Hadronic decays

  • Vtd /Vts: fD and fDs fromLeptonic decays

  • Vub: Form factors of semi-leptonic

    decays

  • Unitarity Test of CKM matrix


Ckm matrix elements measurement
CKM matrix elements measurement for experimentally for a very long time, but none is established.


Precision test of sm and search for new physics
Precision test of SM for experimentally for a very long time, but none is established.and Search for new Physics

  • DDbar mixing

    DDbar mixing in SM ~ 10 –3 -10 –10

    DDbar mixing sensitive to “new physics”

    Our sensitivity : ~ 10-4

  • Lepton universality

  • CP violation

  • Rare decays

    FCNC, Lepton no. violation, ...


Qcd and hadron production
QCD and hadron production for experimentally for a very long time, but none is established.

  • R-value measurement

  • pQCD and non-pQCD boundary

  • Measurement of as at low energies

  • Hadron production at J/y, y’, and continium

  • Multiplicity and other topology of hadron event

  • BEC, correlations, form factors, resonance, etc.


R value measurement
R-value measurement for experimentally for a very long time, but none is established.

Errors on R will be

reduced to 2% from

current 6%


Prospects of glueball searches at besiii
Prospects of glueball searches at BESIII for experimentally for a very long time, but none is established.


J decays are an ideal factory to search for and study light exotic hadrons
J/ for experimentally for a very long time, but none is established. decays are an ideal factory to search for and study light exotic hadrons:

  • The production cross section of J/ is high.

  • The production BR of hadrons in J/ decays are one order higher than ’ decays (“12% rule”).

  • The phase space to 1-3 GeV hadrons in J/ decays are larger than  decays.

  • Exotic hadrons are naively expected to have larger or similar production BR to conventional hadrons in J/ decays.

  • Clean background environment compared with hadron collision experiments, e.g., “JP, I” filter.


One important physics goal of besiii
One Important Physics Goal of BESIII for experimentally for a very long time, but none is established.

With 1010 J/psi events, we hope to answer:

  • Whether glueballs exist or not?

    • Naively, we estimate in each exclusive decay mode:

    • If the eff. is about 20%, we would have 20000 events for each decay mode

       we should observe a relative narrow (width: 50~200MeV) glueball if it exists.


Difficulties i
Difficulties (I) for experimentally for a very long time, but none is established.

  • Theoretically:

    • Predictions on glueball masses from LQCD may be unreliable due to quench approximation.

    • No predictions on the widths so far (even the order).

    • No prediction on the production rate (J/  G).

    • Mix with qqbar mesons or even with 4q, qqg mesons? (dirty?) What is the mixing mechanism from the first principle?


Difficulties ii
Difficulties (II) for experimentally for a very long time, but none is established.

  • Experimentally:

    • Data sample is not big enough (it is not a problem for BESIII)

    • No good way modeling background at low energy, in many cases we have to study bck via data.

    • Interferences among mesons make the mass/Dalitz plots very complicated 

      • PWA is crucial for hadron spectroscopy at BESIII

      • But PWA may face many uncertainties.


About scalar glueball
About scalar glueball for experimentally for a very long time, but none is established.

  • Many scalar mesons in the mass range 1.4~1.8 GeV, where a scalar glueball is predicted to be. More studies will be performed at BESIII.

  • More theoretical studies are also needed:

    • Not only glueball mass, but also width

    • Decay patterns

    • Production rate in J/psi radiative decays

    • Mixing mechanism


2 glueball candidates
2 for experimentally for a very long time, but none is established.++ glueball candidates

  • Lattice QCD predicts the 2++ glueball mass in the range of 2.2~2.4 GeV

  • (2230) was a candidate of 2++ glueball:

    • It was first observed at MARKIII in J/KK

    • It was observed at BES I in J/KK, , ppbar

    • It was not observed at DM2.


Bes i 2230 result
BES-I for experimentally for a very long time, but none is established.(2230) Result

(2230)


The situation at besii
The situation at BESII for experimentally for a very long time, but none is established.

  • The mass plots shows no evident (2230) peaks in J/KK, , ppbar, which is clearly different from BESI.

  • Careful PWA is needed to draw firm conclusion on its existence since it may be still needed in the PWA although no clear mass peak observed.

  • Difficult to draw firm conclusion at present. We hope to give a final answer at BESIII on (2230) .


Other 2 glueball candidates
Other for experimentally for a very long time, but none is established.2++ glueball candidates

  • No other obvious good candidates have been observed in J/psi radiative decays in the mass range predicted by LQCD.

  • What does it mean:

    • LQCD prediction might not be very reliable, or

    • BR(J/  G)xBR(Ghh) is small ( <10-4 ) so that we don’t have the sensitivity to observe it ( quite possible ), or,

    • The width of a glueball is very large ( ~1GeV, E.Klepmt ).


Where to search for the 0 glueball
Where to search for the 0 for experimentally for a very long time, but none is established.-+ glueball?

  • Lattice QCD predicts the 0-+glueball mass in the range of 2.3~2.6 GeV.

  • (1440) and X(1835) were suggested being possible candidates, but their masses are much lower than LQCD predictions.


No 0 glueball candidate observed in the mass range 2 3 2 6 gev
No for experimentally for a very long time, but none is established.0-+ glueball candidate observed in the mass range 2.3~2.6 GeV

  • No evidence for a relatively narrow state ( 100 ~ 200 MeV width ) above 2GeV in

  • Again:

    • LQCD reliable?

    • Production rate could be very low.

    • Glueball width could be very large.


Summary
Summary for experimentally for a very long time, but none is established.

  • Physics at BES (tau-charm threshold) are very rich.

  • There are many exciting discoveries at BESII.

  • BESIII is operational since 2008:

    • Detector performance excellent, ready for physics

    • High quality data samples in hand

    • Analysis in progress, papers in a few months

  • With much more statistics of data sample and much improved detectors at BESIII, more exciting discoveries can be expected.

  • Some fundamental questions, such as the existence of glueballs, might be answered at BESIII with close collaboration with theorists.


Thanks
Thanks! for experimentally for a very long time, but none is established.谢谢!


Prospects a bright future
Prospects: a bright future for experimentally for a very long time, but none is established.

To be decided in Nov.

L ~ 1035-36 cm-2s-1

Expand the life time of tau-charm colliders to > 50 years !

  • BESIII will resume data taking after summer shutdown, ~5 months until next summer

  • Possible plans:

    • 500-1000 M J/y events (2-4 months)

    • 500-1000 M y(2s) (2-4 months)

    • 2fb-1y(3770) (4 months)

    • Lineshape scan of y(3770) (2 weeks)

  • Future charm programs

    • LHCb at CERN(soon)

    • BELLE II at SuperB factory(~ 2014 )

    • PANDA at GSI(~ 2015)

  • New programs under discussion:

    • Frascati(super flavor factory)

    • Novosibirsk(super tau-charm factory)

    • Fermilab

      • TeV fixed target exp. ?

      • Ppbar exp. ?


ad
  • Login