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Transcript of PHOTON MASTERCLASS - Florida State askew/Askew_PhotonHATS_Intro.pdf¢  Our photon...

  • PHOTON MASTERCLASS

  • Ø  Introduction Ø Why contemplate this at all?

    Ø Problems Ø What complicates the matter?

    Ø Scope Ø What will be covered in this class?

    OUTLINE:

    2

  • Ø What drives us to even attempt to measure/identify photons at a hadron collider?

    Ø I mean, isn’t it only Hàγγ?

    WHY CONTEMPLATE THIS AT ALL?

    3

  • JUST A FEW PHYSICS TOPICS:

    4

    (GeV)γ T

    p 40 50 60 70 80 210 210×2 210×3

    je t

    ηdγ ηd γ T

    /d p

    σ3 d

    -310

    -210

    -110

    1

    10

    210

    310

    410

    510

    610

    710

    | < 1.5jetη|

    -1CMS Preliminary 2.14 fb = 7 TeVs

    JETPHOX SHERPA

    | < 0.9 (X8000)γη| | < 1.4442 (X400)γη0.9 < |

    | < 2.1 (X20)γη1.566 < | | < 2.5γη2.1 < |

    Total uncertainty

    50 100 150 200 250 300 350 400 450

    Ev en

    ts / 4

    2 G

    eV

    -210

    -110

    1

    10

    210

    310

    410

    = 8 TeVs-1 dt = 19.2 fbL ∫CMS preliminary bkgγ →jets

    multijet +JetsγZ

    top +jetsγW

    γWV

    Electron Data MC Uncertainty

    -2 = 50 TeV2Λ / W0SM + a

    (GeV) T

    Photon p 100 200 300 400

    R at

    io D

    at a/

    M C

    1

    2

    10 210

    (p b/

    G eV

    ) γγ

    /d m

    σd

    -510

    -410

    -310

    -210

    -110

    -1data 2011, L = 5.0 fb

    DIPHOX+GAMMA2MC

    NNLO γ2

    = 7 TeVsCMS Preliminary

    10 210

    da ta

    /D IP

    H O

    X

    0 1 2

    3 4

    (GeV)γγm 10 210

    N N

    LO γ

    da ta

    /2

    0 1 2

    3 4

    (GeV)γ T

    p 20 30 40 210 210×2

    E v

    en ts

    1

    10

    210

    310

    410 Data

    γ)νµSM W(

    bkgγ →jets

    bkgγ →e

    Other bkg

    -1CMS, L = 5 fb = 7 TeVs

    (b)

    (GeV)γ γ T

    p 0 20 40 60 80 100 120

    Ev en

    ts pe

    r b in

    0

    5

    10

    15

    20

    25

    30

    35 Higgs Mass Region Data Driven Background

    =135 GeVHiggsino=350 GeV, MStopMC Signal: M =300 GeVHiggsino=400 GeV, MStopMC Signal: M =290 GeVHiggsino=300 GeV, MStopMC Signal: M

    -1 = 19.5 fbt dL∫ = 8 TeV, sCMS Preliminary,

    � �

    0 50 100 150 200 250

    N um

    be r o

    f E ve

    nt s

    / G eV

    -210

    -110

    1

    10

    210

    310

    410

    Candidate Sampleγγ QCD + Electroweak Error QCD (fake fake sample) Electroweak

    (1100_720_375)γγGGM (1400_1420_375)γγGGM

    CMS Preliminary

    -1Ldt = 4.04 fb∫ = 8 TeV, s >=1 Jet Requirement

    [GeV]missTE 0 50 100 150 200 250D

    at a/

    Pr ed

    ic tio

    n

    0.2 0.4 0.6 0.8

    1 1.2 1.4 1.6 1.8

    [GeV]missTE [GeV] miss TE [GeV] miss TE [GeV] miss TE

    JGB [GeV] 0 50 100 150 200 250 300 350

    Ev en

    ts /1

    0 G

    eV

    -210

    -110

    1

    10

    210

    310 3jets≥ , γ 1≥ = 7 TeV, s, -1CMS Preliminary, L = 4.7fb

    Data Total Background Total Uncertainties MC Signal (1250/700/225)

    (GeV) T

    Photon p 40 60 80 100 120 140 160 180 200 220

    Ev en

    ts /

    10 G

    eV

    0

    2

    4

    6

    8

    10 =7 TeVs, -1CMS preliminary, 35 pb

    dataγe γW

    γ e →e jet γ e →e e

    background uncertainty

    [GeV]γγM 200 400 600 800 1000 1200 1400 1600 1800 2000

    Ev en

    ts /2

    0 G

    eV

    -310

    -210

    -110

    1

    10

    210

    310 Observed Diphoton +jetγ

    Dijet Systematic Uncertainty

    = 1.75 TeV1 = 0.05, Mk ~

    = 3 TeV S

    = 6, M EDn

    at 7 TeV-12.2 fb CMS

    N um

    be r o

    f E ve

    nt s

    -410

    -310

    -210

    -110

    1

    10

    210

    310

    410

    510

    > 0.5 nsCalibT

    DATA

    + Jets (data)γ

    QCD Multijet (data)

    Drell-Yan/W (MC)

    (MC)γW/Z + Jets +

    + Jets (MC)tt

    Bkg. stat error

    GMSB (100, 2000)

    GMSB (100, 250)

    -1CMS 4.9 fb = 7 TeVs

    [GeV]TE 0 200 400 600 800D

    at a/

    Bk g.

    0

    4

    8

    (GeV)TPhoton E 20 30 40 50 60 70 80

    > (p

    b/ G

    eV )

    AA / <

    T T

    Pb Pb

    d N

    /d E

    10

    210

    310

    410

    510

    610

    710

    810

    910

    1010

    1110

    -1(pp)= 231 nbint L-1bµ(PbPb)= 6.8 int=2.76TeV LNNsCMS

    | < 1.44γη| 4 10×PbPb 0 - 10% 3 10×PbPb 10 - 30% 2 10×PbPb 30 - 100%

    10×PbPb 0 - 100% pp Systematic Uncertainty JETPHOX (pp NLO)

    ( pb

    /G eV

    ) T

    /d E

    σ pp

    d

    10

    210

    310

    410

    510

    610

    710

    810

    910

    1010

    1110

  • Ø Colorless tests of QCD, both in pp and HI Ø Diboson and now Triboson coupling measurements Ø Higgsàγγ sure, but also HàZγ, and Higgsino searches

    Ø Dark matter in monophotons Ø SUSY searches Ø New resonances (Gàγγ for instance) Ø χc and some others Ø Exclusive diphoton production Ø There’s a pretty long list…

    THERE’S A LOT…

    5

  • Ø  There are also accessory things one can learn from converted photons for instance, like material distribution and JES. We’re not really going to cover that here, but it is something that we do.

    Ø  There’s also a lot of the commonality between photons and electrons, so learning about one can begin to inform the other.

    ALSO:

    6

  • Ø  There’s a lot of nice things about photons, they form nice predictable electromagnetic showers (at least if they’re not converted) that we can measure very precisely.

    Ø Unfortunately there are two real problems with photons: Ø Photons are non-redundant: you ONLY get the measurement of

    energy from the ECAL, and you typically have no indication of what vertex the photon came from.

    Ø Jets are EVERYWHERE: any jet which fragments to a significant electromagnetic portion is going to look photon-like to some extent.

    Ø Our photon reconstruction and Photon Identification are built to try to get the best estimate of the photon energy, and discriminate against as much of the jet background as possible.

    THE CHALLENGE

    7

  • Ø  The goal of this workshop is to introduce you to how we reconstruct photons, and the choices that have been made in the algorithms. Ø I want to make these quantities real to you, relate them to what the

    detector actually recorded. No more simply cutting on things from your ntuple!

    Ø Get real hands on experience, and further think critically about the choices that have been made.

    Ø We will mainly concentrate on the present reconstruction, that which is used in the 2012 data, but we’ll look into the future at various points as well. We’ll also look into what past detectors have done, and what our distinguished competition does.

    WHAT WILL WE COVER?

    8

  • Ø  There are three different exercises that have been prepared. Two out of the three are more fun if you have Microsoft Excel, but that’s not strictly necessary.

    Ø We’re not doing C++ coding, and we’re not going to run CMSSW.

    Ø What we’re going to do instead is look at what CMSSW is actually DOING.

    Ø  Each exercise has a lecture that corresponds with it that details what the reconstruction is doing. Then you’ll take the data, and try to put it to work. What I want to do with the rest of this talk is to try to put the other steps of photon reconstruction in context.

    THREE PARTS:

    9

  • Ø We start making “Photon” objects out of “superclusters”, which have had energy corrections applied to them. Ø Exercise 1 is all about how we form these clusters out of energy

    depositions in the ECAL.

    Ø The superclusters that we make “Photons” from, must be at least 10 GeV in ET (calculated from the center of the detector).

    Ø That is almost ALL that is required. Thus why I put “photon” in quotation marks. Most of what lives in this collection is actually jets.

    Ø If you are above 100 GeV (in ET), you enter the “photon” collection.

    Ø If you are below 100 GeV, you must pass a preselection cut.

    PRESENTLY:

    10

  • Ø This is really pretty simple, it’s a cut on the old version of H/E. Here:

    Ø H is the sum of Hcal towers in a cone of ΔR < 0.15 about the supercluster position.

    Ø E is the supercluster energy. Ø You are required to have this ratio be less than 0.5. This is

    a really weak preselection cut.