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  • Production of b ats =7 and 8 TeV

    Vanya Belyaev, Concezio Bozzi, Hans Dijkstra, Sasha Mazurov

    ICHEP approval session6 June 2014

    1/23

  • Motivation

    Bound bb states, which can be produced in different spin configurations, are anideal laboratory for QCD tests. Its like a hydrogen atom in QCD.

    States with parallel quark spins (S=1):S-wave state.P-wave b states, composed by 3 spin statesb(0,1,2). can be readily produced in the radiative decaysof b.b(3P) state recently observed by ATLAS, D0 andLHCb.

    This study:1 Measurement of (NS) (N=1, 2, 3) fraction

    originating from b decays as function of pT().Provides valuable information on Color-Octetmatrix elements.

    2 Measurement of b(3P) mass.

    2/23

  • Previous analysis

    Production of (1S) mesons from b decays in pp collisions ats = 1.8 TeV at CDF, arXiv:hepex/9910025.

    Observation of a new b state in radiative transitions to (1S) and (2S)at ATLAS, arXiv:1112.5154

    Measurement of the fraction of (1S) originating from b(1P) in ppcollisions at

    s =7 TeV, arXiv:1209.0282,

    L = 32 pb1Observation of the b(3P) state at LHCb in pp collisions at

    s =7 TeV,

    LHCb-CONF-2012-020, L = 0.9 fb1.

    )c (GeV/)S(1T

    p6 7 8 9 10 11 12 13 14 15

    ) (%)

    P(1 b) f

    rom

    S(1

    Frac

    tion

    of

    0

    10

    20

    30

    40

    50

    60

    70

    80

    90

    100LHCb

    = 7 TeVs

    )2c) (GeV/+ m() +m(0 0.5 1 1.5 2

    2 cCa

    ndid

    ates

    / 20

    MeV

    /

    0

    50

    100

    150

    200

    250

    300 LHCb preliminary = 7 TeVs

    -10.9 fb

    0 0.5 1 1.5 2

    Pull

    -4-2024

    b(3P)

    3/23

  • In this study

    The results in this study extend the statistical precision of previous LHCbmeasurements and add considerably more decays and higher transversemomentum regions. The measurement of (3S) fraction in radiative b(3P)decay was performed for the first time.

    In each pT() bin calculate:

    (ppb(mP)X)Br(b(mP)(nS))(pp(nS)X) =

    Nb(mP)(nS)N(nS)

    (nS)b(mP)(nS)for each (nS), n = 1, 2, 3 and b(mP),m = 1, 2, 3

    Get N from fits: N from m(+) and Nb from[m(+) m(+)] (for better resolution)Compute efficiency from Monte-Carlo simulation

    4/23

  • Content

    1 Datasets2 Determination of yields3 Determination of b yields in the following decays:

    b(1, 2, 3P) (1S)b(2, 3P) (2S)b(3P) (3S)

    4 Measuring of b1(3P) mass5 Monte-Carlo efficiencies6 Systematic uncertainties7 Results

    5/23

  • Datasets

    Full 2011 dataset ats =7 TeV.

    L = 1 fb1Full 2012 dataset at

    s =8 TeV.

    L = 2 fb1Monte-Carlo simulation of b inclusive decays, generated 62 106events.

    6/23

  • The selection

    Almost the same cuts as are used in the study Measurement of productionin pp collisions at

    s = 2.76 TeV, arXiv:1402.2539

    Description Requirement

    rapidity 2.0 < y < 4.5Track fit quality 2/ndf < 4

    Track pT > 1 GeV/c+ vertex probability > 0.5%

    Luminous region |zPV | < 0.5m and x2PV + y2PV < 100mm2Kullback-Leibler distance > 5000

    Muon and hadron hypotheses logLh > 0Muon probability ProbNN > 0.5

    Trigger lines:L0 L0DiMuon

    HLT1 Hlt1DiMuonHighMassHLT2 HLT2DiMuonB

    7/23

  • The fit model

    9 10 110

    5000

    10000

    15000

    20000

    25000

    30000

    Can

    dida

    tes/

    (40

    MeV/c

    2 )

    m+[

    GeV/c2]

    s = 7 TeV

    6 < p+

    T < 12 GeV/c

    (1S)

    (2S) (3S)

    + transverse momentum intervals, GeV/c6 40

    s = 7 TeV

    s = 8 TeV

    N (1S) 283,300 600 659,600 900N (2S) 87,500 400 203,300 600N (3S) 50,420 290 115,300 400015

    3 Double Crystal Ball functions for signal yields. Tails parameters arefixed from simulation.

    Exponential function for combinatorial background.

    8/23

  • b selection

    In this study photons reconstructed using the calorimeter information.Another approach uses photon conversions in e+e pairs this methodhas better invariant mass resolution, but requires more statistics.Cuts on :

    Transverse momentum of pT() > 600 MeV/cPolar angle of in the + rest frame cos > 0Confidence level of CL() > 0.01

    Dimuon mass windows:

    9 10 110

    5000

    10000

    15000

    20000

    25000

    30000

    35000

    Can

    dida

    tes/

    (12

    MeV/c2

    )

    m+[

    GeV/c2]

    9/23

  • b1,2(1, 2, 3P) (1S) fit model (1)

    10 10.50

    200

    400

    600

    800

    1000

    -4-2

    02

    4

    Can

    dida

    tes/

    (20

    MeV/c2

    )

    m+ m+ + m

    PDG (1S)

    [GeV/c2

    ]

    s = 7 TeVb(1P)

    b(2P)b(3P)b1 b2

    One Crystal Ball (CB) for each b1,2(1P, 2P, 3P) state: 6 CB in totalExclude the study of b0 due to its low radiative branching ratio.Product of exponential and linear combination of polynomials forcombinatorial background.

    10/23

  • b1,2(1, 2, 3P) (1S) fit model (2)Free parameters: yields and backgroundparameters.

    Fixed parameter: b1(1P) to the valuemeasured on combined 2011 and 2012datasets.Linked parameters for b1 and b2signals:

    b2(jP) = b1(jP) + mPDGb2(jP)

    , j=1,2

    b2(3P) = b1(3P) + mtheoryb2(3P)

    Nb = Nb1 + (1 )Nb2( is fixed to 0.5)b2 = b1

    Other linked parameters:b1(2P) = b1(1P) + m

    PDGb1(2P)

    b1(3P) = b1(1P) + mb1(3P)(mb1(3P) measured in this study)

    Fixed parameters from MC study:b1(1P),

    b1(2P)b1(1P)

    ,b1(3P)b1(1P)

    and n parameters of CB.

    (1S) transverse momentum intervals, GeV/c14 40

    s = 7 TeV

    s = 8 TeV

    Nb(1P) 2090 80 5070 130Nb(2P) 450 50 1010 80Nb(3P) 150 40 220 60

    11/23

  • b fits

    10 10.50

    200

    400

    600

    800

    1000

    Can

    dida

    tes/

    (20

    MeV/c2

    )

    m+ m+ + mPDG (1S)[

    GeV/c2]

    LHCbs = 7 TeV

    10 10.50

    500

    1000

    1500

    2000

    2500

    Can

    dida

    tes/

    (20

    MeV/c2

    )

    m+ m+ + mPDG (1S)[

    GeV/c2]

    LHCbs = 8 TeV

    10.2 10.4 10.6 10.8 110

    50

    100

    150

    200

    250

    Can

    dida

    tes/

    (20

    MeV/c2

    )

    m+ m+ + mPDG (2S)[

    GeV/c2]

    LHCbs = 7 TeV

    10.2 10.4 10.6 10.8 110

    100

    200

    300

    400

    500

    600

    Can

    dida

    tes/

    (20

    MeV/c2

    )

    m+ m+ + mPDG (2S)[

    GeV/c2]

    LHCbs = 7 TeV

    10.5 10.6 10.70

    5

    10

    15

    20

    25

    30

    Can

    dida

    tes/

    (20

    MeV/c2

    )

    m+ m+ + mPDG (3S)[

    GeV/c2]

    LHCbs = 7 TeV

    10.5 10.6 10.70

    10

    20

    30

    40

    50

    60

    70

    80C

    andi

    date

    s/(2

    0M

    eV/c2

    )

    m+ m+ + mPDG (3S)[

    GeV/c2]

    LHCbs = 8 TeV

    12/23

  • Mass of b1(3P) in b (3S) decay

    10.5 10.6 10.70

    20

    40

    60

    80

    100

    Can

    dida

    tes/

    (20

    MeV/c2

    )

    m+ m+ + mPDG (3S)[

    GeV/c2]

    LHCbs = 7 and 8 TeV

    The measured on the combined 2011 and 2012 datasetsmb1(3P)=10,510 2 (stat) 6 (syst) MeV/c2 is consistent with the massmeasured in another study with converted photons 10,515.7 3.1 (stat)+1.52.1 (syst) MeV/c2 (very preliminary results).

    ATLAS measured b1 and b2 mass barycenter formb2 mb1 = 12 MeV/c2 and = 0.5:mb(3P) = 10,530 5 (stat) 9 (syst) MeV/c2D0: mb(3P) = 10,551 14 (stat) 17 (syst) MeV/c2

    13/23

  • Data Monte Carlo comparison

    A comparison of the distribution of the relevant observables used in thisanalysis was performed on real and simulated data, in order to assess thereliability of Monte Carlo in computing efficiencies

    0 0.2 0.4 0.6 0.8 10

    0.01

    0.02

    0.03

    0.04

    0.05

    0.06

    0 0.2 0.4 0.6 0.8 10

    0.01

    0.02

    0.03

    0.04

    0.05

    0.06

    0 0.2 0.4 0.6 0.8 1-0.02

    0

    0.02

    0.04

    0.06

    0.08

    0.1

    0 2 4

    0

    0.01

    0.02

    0.03

    0.04

    0.05

    0.06

    0.07

    0.08

    0 2 4

    0

    0.02

    0.04

    0.06

    0.08

    0 2 4-0.02

    0

    0.02

    0.04

    0.06

    0.08

    0.1

    0.12

    0.14

    0 10 20 300

    0.01

    0.02

    0.03

    0.04

    0.05

    0.06

    0.07

    0.08

    0 10 20 30

    0

    0.02

    0.04

    0.06

    0.08

    0.1

    0 10 20 30

    -0.020

    0.020.040.060.08

    0.10.120.140.16

    15 20 25 30 350

    0.01

    0.02

    0.03

    0.04

    0.05

    0.06

    15 20 25 30 35

    0

    0.02

    0.04

    0.06

    0.08

    0.1

    15 20 25 30 35

    0

    0.05

    0.1

    0.15

    0.2

    confidence level confidence level confidence level

    2 of decay tree fitter 2 of decay tree fitter 2 of decay tree fitter

    pT [b(1P)][

    GeV/c2]

    pT [b(2P)][

    GeV/c2]

    pT [b(3P)][

    GeV/c2]

    pT [ (1S)][

    GeV/c2]

    pT [ (1S)][

    GeV/c2]

    pT [ (1S)][

    GeV/c2]

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