Pentaquark Searches at BaBar - Jefferson Lab · 17 Tetiana Berger-Hryn'ova Search for Nfor 5 +/Ξ...

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Transcript of Pentaquark Searches at BaBar - Jefferson Lab · 17 Tetiana Berger-Hryn'ova Search for Nfor 5 +/Ξ...

  • Pentaquark Searchesat BaBar

    Tetiana Berger-Hryn’ova, SLACFor the BaBar Collaboration

  • Tetiana Berger-Hryn'ova2

    Outline

    • Search for Θ+ in Electro- and Hadro-Production

    • Inclusive Search for Strange-PentaquarkProduction in e+e- Annihilation

    • Inclusive Search for anti-Charm Pentaquark Production in e+e- Annihilation

    • Search for Θ*++(pK+) in B decay to the p�K+final state

  • Tetiana Berger-Hryn'ova3

    BaBar/PEP-II

    BaBar DCH• 40 layers, axial and stereo wires.• Covers 92% of solid angle• δpt/pt ~ 0.5 -1.5 %• Particle ID up to 1.3 GeV/c

    • PEP-II is an asymmetric e+e- collider with a CM energy of 10.58 GeV.

    • Peak luminosity = 1.0 1034 cm-2s-1• Integrated luminosity = ~310 fb-1

    BaBar EMC• 6580 CsI(Tl) crystals• E resolution ~2 % at high E.

    Cherenkov Angle(Kaon from D*+ → D0 π+ ,

    D0 → K- π+ sample)

    All Events

    BaBar DIRC•Fused Silica Cherenkov radiator•Covers 80% of solid angle•Particle ID above 600 MeV/c

    BaBar SVT• 5 layers of double-sided

    Silicon strip sensors.

  • Tetiana Berger-Hryn'ova4

    Search for Θ+ in Electro- & Hadro-Production

  • Tetiana Berger-Hryn'ova5

    Electro- and Hadro-Production

    Study Θ+→pKS0 production in interactions with the material of the BABAR inner detector!• Hadroproduction: interactions

    of hadrons produced in e+e-annihilation with detector material

    • Electroproduction: off-beam e- and e+ bent into beampipe (Be) in horizontal plane

    Compare withBABAR

    results

    No signal in CLAS: ~6x more data!~40x more data!

    Interaction Region

    Evidence of Θ+ found in: • real/virtual photoproduction (*)• hadroproduction on hydrogenor nuclear target

  • Tetiana Berger-Hryn'ova6

    Signal region (SR

    Sideband (SB)SB

    pKs0 reconstruction/Detector MaterialPreliminary 233 fb-1 e+ e− data

    p

    KS0pKS0

    Vertexπ+

    π−DOCA < 3 mmKS0 FL > 2 mm

    SVT

  • Tetiana Berger-Hryn'ova7

    z profile e- side

    Ta

    TaBe

    -0.2 < y < 0.7 cm

    -3.1< x < -2.2 cm

    Fe

    e- e+

    Detector Tomography with pKs0 Vertices

    SVT support tube

    DCH inner wall

    Preliminary 233 fb-1 e+ e− data

    SVT

    beampipe

  • Tetiana Berger-Hryn'ova8

    • Remove candidates with associated baryons (p,�,d,t)

    • Look for other associated tracks

    pKS0 Mass Distribution

    No Θ+ signal

    SR

    SB

    Vertices from e-Be interaction (e-production)

    pKS0p,p,d,t;

    π±, K±

    π+π−

    Preliminary 233 fb-1 e+ e− data

    Signal region (SR)

    Sideband (SB)SB

    KS0 Mass Distribution

    No Θ+ signal

    SR

    SB

    All vertices (e- and h-production)

    M(KS0p)/GeV/c2

  • Tetiana Berger-Hryn'ova9

    pK-Λ(1520)SR

    SB

    Association of π±, K± with (p, Ks0) VtxAll vertices (same for e-Be with fewer events)

    No Θ+ signal

    removedK+*(892)

    No Θ+ signal

    SR

    SB

    events with p KS0 K−

    SR-SB

    Ksπ+K+*(892)

    SR

    SB

    events with p KS0 π+

    Prel

    imin

    ary

    233

    fb-1

    e+e−

    data

  • Tetiana Berger-Hryn'ova10

    e-Be ElectroproductionHERMES (e+d→KS0p + X)

    M=1528±3 MeV~5σ

    ZEUS (e-p→e-KS0p + X

    M=1522±3 MeV~5σΣ*(1480)

    Fit uses Σ*(1480) [PDG 1star]Possible acceptance loss in low mass region:(PID requires p(p) >4.1 GeV/c; p(KS0)>3 GeV/c)

    Preliminary233 fb-1 e+ e− data

  • Tetiana Berger-Hryn'ova11

    e+e- InclusivePentaquark Searches

  • Tetiana Berger-Hryn'ova12

    Ξ5- |dss(uu,dd)〉

    Ξ−π-

    Overview

    0

    10

    20

    30

    40

    50

    60

    a)

    Ent

    ries

    / 7.

    5 M

    eV/c

    2M(Ξπ) [GeV/c2]

    -10

    0

    10

    20

    30

    1.4 1.6 1.8 2 2.2 2.4 2.6 2.8

    b)

    • Exotic resonances: Θ+, seen by several and Ξ50,-- seen by one experiments.

    • Fits into several models;10+8 multiplet of SU(3)f is favored.

    • Production could be similar to baryons of same mass.

    0

    5

    10

    15

    20

    25

    30

    35

    40

    1.4 1.6 1.8 2 2.2 2.4

    M(nK+) (GeV/c2)

    Eve

    nts

    / 20

    MeV

    /c2

    05

    10152025303540

    1.5 2M(nK+) (GeV/c2)

    Θ+ |ududs〉

    ΛK-, Σ0K- ΛK0S, Σ0K0S

    NA49

    CLAS

    ΛK+, Σ0K+N5+ |uud(dd,ss)〉N50 |udd(uu,ss)〉

    pK0S

    ΛK0S, Σ0K0S

    Ξ5- - |sdsdu〉 Ξ50 |uss(uu,dd)〉 Ξ5+ |ususd〉

    Σ5+ |uus(dd,ss)〉

    Σ50 |uds(u�,d�,s�)〉

    Σ5- |dds(uu,ss)〉 pK0S

  • Tetiana Berger-Hryn'ova13

    Search for Θ+/Σ5+→ pKS0• Proton selection using

    dE/dx and Cherenkov, clean over wide momentum range.

    • Use K0S → π+π−.• 3x106 reconstructed

    decays• Expected Resolution

    (HWHM) on Θ+ mass ~ 2 MeV (from MC)

    • Can also look for Σ5+.

    → ~98K ΛC’s in data sample→ Resolution 5-7 MeV at ΛCmass

    123 fb-1 PRL 95, 042002 (2005)

    No Σ5+×103

    Can

    dida

    tes/

    (2 M

    eV/c

    2 )Upper Limits of total cross section:

    Θ++Θ- : for Γ=1(8)MeV ⇒171(363)fb

  • Tetiana Berger-Hryn'ova14

    Search for Ξ50/--→ Ξ-π±

    Λ

    πΞ−

    −πΞ

    p+−πΛ

    IP

    0

    24,000 entries

    8000 entries

    No signal of Ξ50 / Ξ5--

    Mass resolution~8 MeV/c2 in Ξ5region (r.m.s)

    • Geometrical selection of two displaced vertices• Good p and π selection (dE/dx, θc)• Select masses near the nominal Λ0 and Ξ- masses• Control signals: Ξ*0(1530) Ξ-π+, Ξc(2470) Ξ-π+

    PR

    L 95

    , 042

    002

    (200

    5)

    U. L. on total cross section: Ξ5+++Ξ5-- : for Γ=1(18)MeV ⇒ 25(36) fb

  • Tetiana Berger-Hryn'ova15

    1.106 1.108 1.11 1.112 1.114 1.116 1.118 1.12 1.122 1.124 1.1260

    2000

    4000

    6000

    8000

    10000 Λ

    0.475 0.48 0.485 0.49 0.495 0.5 0.505 0.51 0.515 0.520

    2000

    4000

    6000

    8000

    10000

    K0S

    Search for Ξ50/N50 → ΛK0S

    π−

    π+

    K0 s

    p+

    π−

    ΜΜppππ [GeV][GeV]

    ΜΜππππ [GeV][GeV]2.4 2.42 2.44 2.46 2.48 2.5 2.52 2.540

    200

    400

    600

    800

    1000

    NΞc ≈ 1100σ = 5.9 MeVΞC

    0

    (GeV)S0 KΛm

    1.6 1.8 2 2.2 2.4 2.6 2.8 3

    Entri

    es p

    er 2

    MeV

    0

    200

    400

    600

    800

    1000 0cΞ

    - p* < 3 GeV- p* > 3 GeV (scale 10)

    05N

    (GeV)S0 KΛm

    1.7 1.75 1.8 1.85 1.9 1.95 2

    En

    trie

    s p

    er 2

    MeV

    0

    200

    400

    600

    800

    1000

    ΛK0S

    123fb-1 hep-ex/0408064

    No Ξ50 signal

  • Tetiana Berger-Hryn'ova16

    (GeV)- KΛm1.6 1.8 2 2.2 2.4 2.6 2.8 3

    En

    trie

    s p

    er 2

    MeV

    0

    1000

    2000

    3000

    4000

    5000

    6000

    7000

    - p* < 3 GeV

    - p* > 3 GeV (scale 10)

    ΛK−

    (GeV)- KΛm1.7 1.75 1.8 1.85 1.9 1.95 2

    En

    trie

    s p

    er

    1 M

    eV

    0

    500

    1000

    1500

    2000

    2500

    1.65 1.655 1.66 1.665 1.67 1.675 1.68 1.685 1.69 1.695 1.70

    200

    400

    600

    800

    1000

    1200

    1400

    1600

    1800

    Ω−

    (GeV)+ KΛm1.5 2 2.5 3 3.5 4 4.5 5

    Ent

    ries

    per

    2 M

    eV

    0

    2000

    4000

    6000

    8000

    10000

    12000

    14000

    16000

    18000

    20000

    +cΛ

    feed-down+cΛ

    - p* < 3 GeV

    - p* > 3 GeV (scale 10)

    +5N

    ΛK+

    Search for N5+→ Λ K+, Ξ5- → Λ K-123 fb-1 hep-ex/0408064

    (GeV)+ KΛm2.24 2.25 2.26 2.27 2.28 2.29 2.3 2.31 2.32 2.33 2.34

    En

    trie

    s p

    er

    2 M

    eV

    0

    50

    100

    150

    200

    250

    300

    = 615.7+cΛ

    N

    RMS = 5.3 MeVDATA

    NΛc ≈ 600σ = 5.3 MeV

    Λc+ Cabibbo-Suppressed Decay

    NΩ ≈ 6300σ = 3.0 MeV No Ξ5− signal

  • Tetiana Berger-Hryn'ova17

    SearchSearch for for N5+/Ξ5-→Σ0K±, Ξ50/N50→Σ0Ks0

    00sKΣ

    p*>3

    GeV

    1<p*

  • Tetiana Berger-Hryn'ova18

    Results (e+e- Annihilations)• No signal for any

    pentaquark state observed

    • Assumptions– J=1/2– BF(Θ+ pKs0)=25%– BF(Ξ5-- Ξ-π+)=50%– BF for Ξ5- and Ξ50 very

    unclear– Intrinsic width 1-18 MeV/c2

    • Limits on production times branching fraction 4-15x lower than production rates for conventional baryons

    123 fb-1 PRL 95, 042002 (2005)

  • Tetiana Berger-Hryn'ova19

    Θc0 Pentaquark Search

    Θ+(udud�)

    Ξ−−(sdsd�)Ξ+(usus�)

    Θc0(udud�)

    SU(4) 60-plet 15-pletC=+2

    anti-15+ 6-pletC=+1

    anti-6-pletC=-1

    C

    Y

    I

    anti-decupltet (10)+ octet (8)

    C=0

    (cdsd�)

    (cdcd�)

    D0→K-π+ mode only

  • Tetiana Berger-Hryn'ova20

    After cuts~55k D*-~4k bkgr

    After cuts~73k D*-~62k bkgr

    D*-(�0→K+π−)

    D*-(�0→K+π−π+π−)

    Search for Θc0→pD*-(�0(K+π−,K+π−π+π−)π−)BaBar Preliminary 123 fb-1 e+ e− data, see hep-ex/0510044 for details

    with

    pro

    ton

    requ

    irem

    ent

    Expected Resolution (HWHM) on Θc mass ~ 3 MeV (from MC)

    Reconstruct ~750k of D*-

  • Tetiana Berger-Hryn'ova21

    Θ*++ Pentaquark Searchin B-decay

  • Tetiana Berger-Hryn'ova22

    • Theory: Θ*++→ K+p mode dominant mΘ*++ = 1.6-1.7 GeV/c2 & ΓΘ*++= 37-66 MeV

    • Not seen by CLAS, HERMES, SAPHIR, ZEUS• A hint from STAR? (at ~1.53GeV/c2, Γ~20MeV); isospin partner not seen

    in BaBar inclusive search with ~3-10 times statistics

    • In K+p scattering: no sign of Θ*++; constrains Γ(Θ*++)

  • Tetiana Berger-Hryn'ova23

    Analysis Overview• Data Samples

    – 210 fb-1 on the ϒ(4S) resonance (232 M B± mesons)

    • Isolate B±→p�K± final state, search for Θ*++ in mpK+

    • Major Backgrounds:– Baryons from e+e-→q�, where q=u,d,s,c (suppress

    topologically)– Allowed B decays: B± →XK±, X→p� (X=ηc,J/ψ,χc,ψ(2S))

    u

    ud

    u�uB

    +

    Θ*++u

    B+

    u

    uW+Θ*++u

    d

    e+ e-B decay

    e+ e-

    PRD 72, 051101(R) 2005

    q�

  • Tetiana Berger-Hryn'ova24

    ηc

    J/ψ

    ψ(2S)

    B→ppK Dalitz Plot

    p�K+ signal box 780 events: ~566±29 signal events ~ 202±5 combinatorial

    background

    Sideband: 1661 events

    χc[0-2]

    Θ*++ region

    m p�

    ~mB

    E* B

    -E* B

    expe

    cted

    B signal

  • Tetiana Berger-Hryn'ova25

    Remove from UL calculation

    Events with 2.853.15GeV/c2

    Θ*++ Search(PRD 72, 051101(R) 2005)

    For mpK+

  • Tetiana Berger-Hryn'ova26

    Conclusions

    • BaBar Pentaquark searches have yielded negative results• High statistics, excellent mass resolution:

    – Hadro- and Electro-Production in Detector Material• No Θ+→pKs found

    – Inclusive Search in e+e- Annihilations• No evidence found for eight members of strange anti-decuplet

    and octet, and anti-charm Θc0• Limits below expectation for baryons (factor 1-15) for Θ+, Ξ5--

    • Low statistics/low background, excellent mass resolution:– No Θ*++ observed in B+→p�K+: limit set on product of BF

    • Pentaquark Searches highlight potential for study of charmed and non-charmed Baryons at BaBar

  • Backup Slides

  • Tetiana Berger-Hryn'ova28

    p and Ks0 Samples

    lab. momentum of KS lab. momentum of p

    Signalregion (SR)

    Sideband(SB)

    Sideband

    S/B

    flight length [cm]

    Very good S/Bbehaviour withflight length

    • Clean samples of selected p and Ks → π+π- candidates

  • Tetiana Berger-Hryn'ova29

    Combine p or KS with identified π-- or K++

    K*-(892)

    Λ(1115)

    π−−

    π−−

    π−−

    Remove K*(892)

    Κ++

    SR

    SR

    SB

    SB

    SR

    SB

    SR-SB

    No Θ+ Seen

  • Tetiana Berger-Hryn'ova30

    Zeus Comparison

  • Tetiana Berger-Hryn'ova31

    Upper Limits for Production Cross Section

    UL @ 95% CL on production Xsection:

    Γ= 1 Γ = 8 MeV

    < 182.8 < 363.1 fb

    < 5.4x10-5 < 10.7x10-5 per q� event

    < 17.9x10-5 < 35.0x10-5 per ϒ(4S)

    Sample Bin: 3.0 GeV < p* < 3.5 GeV

    yield

  • Tetiana Berger-Hryn'ova32

    Search for Θc0

  • Tetiana Berger-Hryn'ova33

    Hints of a signal?

    STAR

    mpK+, GeV/c2

    d-Au

    STA

    R P

    relim

    inar

    y

    Au-Au

    Θ++?

    Puzzle: BaBar didn’t observe the Θ*++ isovector partner Θ*+ in the search of pK0S resonances

    d-Au

    Θ++?

    From Volker D Burkert’s talk at LP05

    pK+ and �K- d-Au at 200GeVcombinatorial & correlated pairs

    Bkgr subtracted

    Bkgr subtracted

    Can

    dida

    tes/

    (5M

    eV/c

    2 )

    SuppressedZero!

    ×103

  • Tetiana Berger-Hryn'ova34

    ,||

    ,2)1cos3(||*

    0

    2*2 ,

    ∑∑

    =

    −=

    i i

    i Thri

    pL

    pLiB

    θ

    e+e-→q�Background Suppression

    e+ e-

    q�

    e+ e-

    B decay

    (i = photons and tracks which are not part of the BppK) and

    angles between the BppK thrust (momentum) and z axis

    combined into Fisher Discriminant

    SignalMCBackground

    67%94%

  • Tetiana Berger-Hryn'ova35

    mES ΔE Signal MC

    mES, GeV/c2

    Even

    ts/3

    MeV

    /c2

    Even

    ts/1

    0MeV

    B reconstruction22

    22

    2 BiBiCM

    ES pEppEm −⎟⎟

    ⎞⎜⎜⎝

    ⎛⋅+=rr

    ΔE, GeV

    2EEΔE CM*B −=

    σΔE=16.7MeV

    σmES=2.7MeV/c2

    Off-resonance Data

  • Tetiana Berger-Hryn'ova36

    B±→p�K± Signal Event Yield

    Event estimate in the signal region for 1D fits to data: ΔE fit: 566±29 events && mES fit: 588±32 events

    Expected Charmonium contribution: ~229±33

    ΔE mES

    5.276