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Quarkonia spectroscopy at CDF. Heavy Quarkonia 2006. Ulrich Kerzel, University of Karlsruhe for the CDF collaboration. Content: X(3872) m(  +  - ) mass spectrum quantum numbers J PC search for  b. Heavy quark physics at the Tevatron. huge inelastic cross-section:

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quarkonia spectroscopy at cdf

Quarkonia spectroscopy at CDF

Heavy Quarkonia 2006

Ulrich Kerzel, University of Karlsruhe

for the CDF collaboration

  • Content:
  • X(3872)
    • m(+-) mass spectrum
    • quantum numbers JPC
  • search for b
heavy quark physics at the tevatron
Heavy quark physics at the Tevatron
  • huge inelastic cross-section:
  • ¼ 5000 times bigger than for
  • )triggers are essential!
  • events “polluted” by fragmentation tracks, underlying event, pile-up
    • ) need precise tracking and good resolution
  • dedicated trigger for
    • J/!+-: m(+-) around m(J/)
    • ) high quality J/ events with large statistics(channel J/! e+e- much more challenging in hadronic environment)
    • lepton + track with large IP (semi-leptonic B decay)
    • two tracks with large IP (hadronic B decay)

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

the x 3872
The X(3872)
  • discovered 2003 by Belle in search for charmonium states
  • m(+-) spectrum compatible with 0
    • CDF PRL 96,102002 (2006)
  • mass: m = 3871.3 § 0.7 § 0.4 MeV/c2
    • CDF PRL 93,072001 (2004) ,
    • width compatible with detector resolution
    •  < 2.3 MeV/c2Belle PRL 91,26001 (2003)
  • No X++ or X– --CDF PRL 93,072001 (2004)
  • No iso-partner X§BaBar PRD 71, 031501 (2005)
  • Evidence for X ! J/ , J/ 
    • Belle hep-ex/0505037

(2S) ! J/ +-

known resonance

  • ) what is the X(3872)? charmonium? exotic?
  • ! determine quantum numbers JPC
      • m(+-) sensitive to JPC
      • use distribution of angles between decay particles to measure JPC

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

m mass spectrum for 2s
m(+-) mass spectrum for (2S)
  • (2S) in same exclusive final state
  • m(+-) spectrum known:
  • s-wave with small
  • d-wave contribution
  • e.g. model by
  • Novikov-Shifman

) high precision data by CDF

) allows to discriminate between models

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

slide5

The m(+-) mass spectrum

Mass spectrum sensitive to JPC

if (+-) in s-wave state:

shape needs to be modelled

e.g. multipole expansions for

if (+-) in p-wave state:

shape follows Breit-Wigner

e.g. decay via 0!+-

  • m(+-) favours high end of mass spectrum
    • )compatible with intermediate 0!+- resonance
  • also 3S1 multipole-expansion for charmonium possible
    • no charmonium candidate at that mass
    • 3S1 also has JPC = 1-- ) non-observation by BES
    • ((e+e-)B(+-J/) < 10 eV @90% C.L. )

notation: n2s+1LJ (JPC)

Phys.Lett.B579:74-78 (2004)

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

slide6

The m(+-) mass spectrum

  • for broad resonances (0):
  • kinematic quantities vary across width
  • introduce form-factor
    • e.g. Blatt-Weisskopf
    • depends on ang. momentum L,
    • effective range R
    • ) affects shape for L=0, L=1
  • Possible 0 -  mixing:
  •  mass contribution far from pole position
  • interference 0$ possible

)L=0 and L=1 both compatible with m(+-) spectrum

)mixing phase of 95± describes data

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

determination of j pc 1
Determination of JPC (1)

definition of angular variables:

example: JPC assumptions

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

determination of j pc 2
Determination of JPC (2)
  • Predictions for kinematic decay quantities fromhelicity formalism:
    • )decay chain as sequential 2-body decays
    • X(3872) ! J/ (+-)s,p !+-+-
    • need:
      • one matrix element per decay vertex
      • propagators to connect vertices
    • matrix elements: angular part A and kinetic part T
    • assume state with lowest L dominates, neglect others
  • dedicated simulation for each JPC hypothesis
    • (including detector effects)
  • compare to angular distributions measured in data via 2

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

determination of j pc 3
Determination of JPC (3)
  • Limitations from helicity formalism:
  • no model-independent description of +- in s-wave
  • Breit-Wigner for 0!+- depends on form-factor details
    • ) fix m distribution to match the data
    • )analyse angular distributions only
    • N.B. 0 and  have both JPC = 1- -
    • ) angular distributions not affected by potential interference
  • JPC = 1-+ and 2-+: multiple sub-states with same L contribute
  • ) Can an arbitrary mixture describe the data?

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

result for 2s
Result for (2S)

obtain expected result:

JPC = 1- -

  • Exploit correlations between angles via 3D fit:
  • 3 bins in 
  • 2 bins in J/
  • 2 bins in 

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

result for x 3872
Result for X(3872)

Only JPC = 1++ or 2-+ compatible with data!

All other tested hypotheses excluded by > 3

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

what is the x 3872
What is the X(3872) ??
  • Charmonium ?

potential candidates:

but:

      • decay via 0: isospin violating
      • mass predictions from potential models ¼ 50-100 MeV/c2 off
  • exotic?
    • m(X) ¼ m(D0) + m(D0*) ! coincidence?
    • charmed molecule ? ( or or ...)
    • hybrid state, i.e. ? (but expected above ¼ 4 GeV/c2)
    • mainly charmonium - but interaction with ?

notation: 2s+1LJ (JPC)

e.g. M. Suzuki hep-ph/0508258

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

x 3872 with neural networks
X(3872) with neural networks
  • Use sophisticated neural networks for
  • “next generation” X(3872) analyses:
  • exploit correlations between variables
    • ! improved candidate selection
  • train networks for multiple
  • JPC assignments
    • further handle to test hypotheses:
      • “good” hypotheses
      • ! higher significance
      • to be used in likelihood analyses
  • strong suppression of combinatorial BG
    • ! to be used in search for
    • partner of X(3872) in B system:

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

search for b 1
Search for b (1)
  • ground state of system
  • test NRQCD:
    • ~30-160 MeV/c2 lighter than
  • not yet observed, searches:
    • LEP !b
    • CLEO
    • 2 evidence from CDF RunI
  • search in exclusive final state:
  • b! J/  J/  !+-+-
  • JPC: 0-+! 1- - 1- -
  • BR(!) ¼ 40%
  • BR(c!) ¼ 3¢ 10-3
  • expect BR ¼ 7¢ 10-5 – 7¢ 10-3

Phys. Rev. D 63, 094006 (2001)

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

search for b 2
Search for b (2)
  • use 1.1 fb-1 data from J/!+- trigger
  • candidate selection:
  • b! J/ J/
  • 2 of vertex fit < 18.5
  • || < 0.6
  • pt (b) > 3 GeV/c
  • J/ (1): J/ ! +- trigger
  • || < 0.6
  • pt (J/ ) > 3 GeV/c
  • pt (§) > 2.0 GeV/c
  • J/ (2):  + track
  • pt(J/) > 3 GeV/c
  • pt(§) > 2 GeV/c (||<0.6) or
  • > 3.5GeV/c (0.6 < || < 1.0)
  • pt(track) > 1.5 GeV/c
  • dE/dx residual < 3.7
  • (track)

pt(J/) > 50 GeV/c

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

search for b 3
Search for b (3)
  • after cuts:
    • 3 candidates observed in 9.0 – 9.5 GeV/c2,
    • expect 3.6 background events
    • ) no significant evidence of b
  • ) upper limit on b production cross-section

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

conclusions outlook
Conclusions & Outlook
  • Tevatron and CDF performing well, rich B physics programme
  • New results on X(3872):
    • 3D angular analysis: JPC = 1++ or 2-+
    • m(+-):
      • both L=0 or L=1 transition via 0 compatible with data

) cannot exclude J-+ hypotheses from m(+-)

      • possibly 0$ interference with =95±

) both charmonium and exotic interpretation still “in the game”

    • further analyses using neural networks started
    • ongoing search for

in molecular picture: expect further states similar to X(3872), e.g.

  • Search for b! J/ J/:
    • no signal observed, upper limit on production cross section

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

backup
BACKUP

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

tevatron run 2
Tevatron Run 2
  • 1 fb-1 delivered June 2005
  • ¼ 15-20 pb-1/week delivered before spring 2006 shutdown

1 fb-1 delivered

  • analyses presented use ¼ 0.3 – 1.0 fb-1
  • (“good data”)

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

slide20

The Tevatron

CDF

D0

Tevatron

RunI: 1992 – 1996

data taking period at

RunII: 2001 – 2009

major upgrades to

collider and

detectors

Main injector

and recycler

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

tevatron performance
Tevatron performance

1 fb-1

Running well - both peak luminosity and integrated luminosity

before spring 2006 shutdown: ~15-20 pb-1 / week delivered

1 fb-1 delivered in beginning of June 2005 .

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

the cdf detector
The CDF detector
  • precise tracking: silicon vertex detector and drift chamber
  • important for B physics: direct trigger for displaced vertices, J/ !+-

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

slide23

Physics at the Tevatron

  • large b production rates:
  • ) 103 times bigger than !
  • spectrum quickly falling with pt
  • Heavy and excited states not produced at B factories:
  • enormous inelastic cross-section:
    • ) triggers are essential
  • events “polluted” by fragmentation tracks, underlying events
    • ) need precise tracking and good resolution!

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

dedicated trigger j
Dedicated trigger J/!+-

Evaluate muon chamber info on trigger level:

  • trigger events where m(-)around m(J/ )
  • high quality J/  events
  • large statistics available

N.B. channel J/ ! e+e- much more challenging in complex hadronic environment!

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

x 3872 with j e e
X(3872) with J/! e+ e-

Reconstruction of J/! e+e- very difficult

in complex hadronic environment

strong radiative tail

  • dedicated J/! e+e- trigger
  • use neural-network based approach to identify soft e§ (pt > 2GeV/c)
  • reject e§ from conversions based on neural network approach
  • add  at J/ vertex to accommodate Bremsstrahlung
  • X(3872) reconstructions follows
  • J/!+- case

) able to reconstruct X(3872) in this channel!

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

x 3872 production fraction from b
X(3872) production fraction from B

fraction from B decays:

(2S): 28.3 §1.0 (stat.)

§ 0.7 (syst.) %

X(3872): 16.1 § 4.9 (stat.)

§ 1.0 (syst.)%

) X(3872) behaves similarly to the (2S)

(with given uncertainties)

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

the m mass spectrum
The m(+-) mass spectrum
  • Distribution of m(+-) constrains quantum numbers JPC
  • shape depends on:
  • decay of (+-) sub-system: (+-) in s or p wave
    • (i.e. intermediate sub-resonance or not)
  • relative angular momentum between (+-) and (+-)
  • (and detector acceptance, efficiency, etc.)

e.g. for decay chain: X ! J/0; 0!+-

spectrum described by

Breit – Wigner function

for broad resonances (kinematic factors vary across width)

form-factor

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

the m mass spectrum1
The m(+-) mass spectrum
  • Challenge: Large background, rather low X(3872) yield
  • ) sideband-subtraction difficult, instead:
  • “slicing technique”
  • impose bin borders in m(+-) as additional cuts
  • fit resulting (+-+-) mass spectrum
  • obtained yield shows variation with m(+-)

need to be careful at kinematic borders

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

influence of form factor on m
Influence of form-factor on m(+-)

use: model from Blatt-Weiskopf:

parameter “R” determines effective size, no unique choice

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

mixing phase between and
Mixing phase between  and 

good fit probability found

for relative phase

¼ 95±

Relatively small influence

of 0 form-factor radius,

large effect from X(3872)

form-factor radius.

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

effect of 0 mixing
Effect of 0-  mixing

)Neither L=0 nor L=1 can be ruled out from m(+-) alone

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

illustration of angular correlation
Illustration of angular correlation

example for JPC = 1++

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

sample fit for x 3872 angular analysis
Sample fit for X(3872) angular analysis

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

helicity matrix element
Helicity matrix element
  • treat initial and final state in respective rest-frame
  • two body decay:
    • are back-to-back
    • common quantisation axis
    • )final state helicity  = 1 - 2

using Wigner D functions

assume lowest angular momentum L is dominant

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

transition weight from helicity matrix element
Transition weight from Helicity matrix element

incoherent sum over

final states

coherent sum over

intermediate states

mean over

initial state

in case of several substates:

coherent sum contains a priori

unknown mixing constant gLS

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

x 3872 fit results
X(3872) fit results

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

systematics for x 3872
Systematics for X(3872)

systematics:

13 – 17:

details of MC

12:

use phase-space

to describe m()

10, 11:

vary 0 form-factor radius

6-9:

vary X(3872) mean

and width

4,5:

vary histogram bin width

2,3:

vary X(3872) fit window

1: default result

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

2s fit results
(2S) fit results

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

systematics for 2s
Systematics for (2S)

systematics:

13 – 17:

details of MC

6,7 :

vary (2S) mean

and width

4,5:

vary histogram bin width

2,3:

vary (2S) fit window

1: default result

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

detector effects

 for JPC = 1--

Detector effects

Detector acceptance, resolution and cuts affect angular variables:

original

after simulation

 for JPC = 1++

left: 1++

right: 1--

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

charmed molecule

0

Charmed molecule?

e.g. DeRujula, Georgi, Glashow (1977)

?

possible formation of “molecules”:

decay via:

binding by 0

TörnqvistPhys. Lett. B590, 209-215 (2004)

SwansonPhys. Lett. B588, 189-195 (2004)

similar to deuteron: small attractive force mediated by 0

predict JPC = 1++ or 0-+

isospin breaking via 0!+- allowed

Swanson: additional contribution from , 0, only JPC = 1++

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

deuson model t rnqvist

0

„Deuson“ model (Törnqvist)
  • X(3872) similar to deuteron:
  • composed of two objects
  • bound by 0 exchange
  • Prediction:
  • JPC = 1++ or 0-+
    • (otherwise potential too weak or repulsive)
  • small binding energy:
    • narrow resonance, big object
  • isospin breaking:
    • X! J/0, 0!+- allowed
    • X! J/forbidden for any isoscalar 
    • X! J/ 00 forbidden

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

further properties by b factories
Further properties by B-factories

(hep-ex/0408083)

  • BaBar:
    • search for charged partner X§! J/§
      • expect twice the rate if X is part of iso-triplett

) no signal found

  • Belle:
    • 4  evidence for decay X(3872) ! J/
    • evidence for decay X! J/+-0

)Swanson: 1++

has contribution of X ! J/, ! +-0

    • search for X!c1, X!c2

) no signal found

C = +1

(hep-ex/0505037)

(hep-ph/0311229)

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

excited b mesons
Excited B mesons

narrow: ~ 10 MeV/c2

broad : ~ 100 MeV/c2

similar picture for Bs**

Heavy Quark Effective Theory:

hydrogen atom like system with

heavy + light quark

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

exclusive b d
Exclusive Bd**

experimental observable:

Q = m(B**) – m(B) – m()

(free remaining kinetic energy)

  • focus on narrow states:
    • B1! B*
    • B2*! B 
    • B2*! B*
    • ( not reconstructed)
  • exclusive analysis
    • ) high resolution

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

exclusive b
Exclusive B**

HQET:

hydrogen atom like system with

heavy + light quark

  • focus on narrow states:
    • B1 , B2*! B*
    • B2*! B 
  • Towards Bs¤¤:
  • similar to Bd¤¤: Bs¤¤! B§ K¨
  • situation much less clear:
  • signal so far from DELPHI, OPAL, D0
  • exclusive B§! J/ K§ , B§! D §
  • sophisticated neural networks to suppress background
  • expect result ~summer

observable:Q = m(B**) – m(B) – m(/K)

(free remaining kinetic energy)

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

towards b s
Towards Bs**

Delphi Conf 2005-011 Conf 731

  • Bs¤¤! B§ K¨ observed by:
  • DELPHI (inclusive)
  • D0 (exclusive)
  • OPAL (inclusive)

Z. Phys. C66 (1995) 19

  • Rare signal dominated by large background
  • ! deploy sophisticated neural networks
    • B§! J/ K§, B§! D §
    • Bs¤¤ resonant signal vs. combinatorial background
    • ) expect CDF result this summer

D0Note 5027-Conf

U.Kerzel, University of Karlsruhe ---- Workshop on Heavy Quarkonia

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