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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

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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 JPC

  • search for b


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)

  • 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)

  • (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


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


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 JPC (1)

definition of angular variables:

example: JPC assumptions

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


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 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)

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)

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) ??

  • 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

    • 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)

    • 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)

    • 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)

    • 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

    • 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

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


    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


    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

    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

    • 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


    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/!+-

    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-

    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

    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

    • 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 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(+-)

    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 

    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

    )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

    example for JPC = 1++

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


    Sample fit for X(3872) angular analysis

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


    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

    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

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


    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

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


    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


     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


    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


    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

    (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

    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 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**

    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 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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