μ + e - Liza Sneitzer 4/22/11 - PowerPoint Presentation

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μ+ e-

Liza Sneitzer

4/22/11

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mu+ e-

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V

e

Red

0 Blue

b

Green

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el_type:Red truth:Black

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The electron identification in the forward region (2.5 < |η | < 4.9) is essential in many physics analyses, including electroweak measurements and new phenomena searches. In contrast to the central electron, the forward electron reconstruction uses only the information from the calorimeters as the tracking sys- tem is limited to |

η

| < 2.5. Obviously it is not possible to distinguish between electrons and photons. Preselection and identification are done in the same algorithm. The variables used to discriminate between electrons and hadrons are defined as the topological-cluster moments or combinations of them. This is done separately in two

η bins: the EMEC Inner Wheel and the FCal

using a cut-based technique. Current limitations on detector measurement and reconstruction software mean that electrons can be identified up to |

η

| < 4.9; and with the lack of tracking electrons reconstructed here do not have associated charge. An electron candidate in the forward calorimeters is reconstructed if there is a cluster with E

T

> 5

GeV

. The direction of the electron is defined by the

barycenter

of the cells belonging to the cluster in the calorimeter.

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From MC numbering scheme: The graviton and the boson content of a two-Higgs-doublet scenario and of additional SU(2)×U(1) groups are found in the range 31–40.

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LQ

C

v

e

b

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e

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0 Blue

b

Green

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e

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0 Blue

b

Green

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WW to mu+ e-

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Typically for CSC note, the selection levels were the following :

* Loose cuts

: This set of cuts performs a simple electron identification based only on limited information from the calorimeters. Cuts are applied on the

hadronic

leakage and on shower-shape variables, derived from only the middle layer of the EM calorimeter (lateral shower shape and lateral shower width). This set of cuts provides excellent identification efficiency, but low background rejection.

*

Medium cuts

: This set of cuts improves the quality by adding cuts on the strips in the first layer of the EM calorimeter and on the tracking variables: * Strip-based cuts are effective in the rejection of

π

0 →

γγ

decays. Since the energy-deposit pattern from

π

0 ’

s

is often found to have two maxima due to

π

0 →

γγ

decay, showers are studied in a window ∆

η

×∆

φ

= 0.125×0.2 around the cell with the highest ET to look for a second maximum. If more than two maxima are found the second highest maximum is considered. The variables used include ∆Es = Emax2 −

Emin

, the difference between the energy associated with the second maximum Emax2 and the energy reconstructed in the strip with the minimal value, found between the first and second maxima,

Emin

. Also included are: Rmax2 = Emax2 /(1 + 9 × 10−3 ET ), where ET is the transverse energy of the cluster in the EM calorimeter and the constant value 9 is in units of GeV−1 ;

wstot

, the shower width over the strips covering 2.5 cells of the second layer (20 strips in the barrel for instance); ws3 , the shower width over three strips around the one with the maximal energy deposit; and

Fside

, the fraction of energy deposited outside the shower core of three central strips. * The tracking variables include the number of hits in the pixels, the number of silicon hits (pixels plus SCT) and the

tranverse

impact parameter. The medium cuts increase the jet rejection by a factor of 3-4 with respect to the loose cuts, while reducing the identification efficiency by ∼ 10%.

*

Tight cuts

: This set of cuts makes use of all the particle-identification tools currently available for electrons. In addition to the cuts used in the medium set, cuts are applied on the number of

vertexing

-layer hits (to reject electrons from conversions), on the number of hits in the TRT, on the ratio of high-threshold hits to the number of hits in the TRT (to reject the dominant background from charged hadrons), on the difference between the cluster and the extrapolated track positions in

η

and

φ

, and on the ratio of cluster energy to track momentum, as shown in Table 3. Two different final selections are available within this tight category: they are named tight (

isol

) and tight (TRT) and are

optimised

differently for isolated and non-isolated electrons. In the case of tight (

isol

) cuts, an additional energy isolation cut is applied to the cluster, using all cell energies within a cone of ∆R < 0.2 around the electron candidate. This set of cuts provides, in general, the highest isolated electron identification and the highest rejection against jets. The tight (TRT) cuts do not include the additional explicit energy isolation cut, but instead apply tighter cuts on the TRT information to further remove the background from charged hadrons.

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Mothertype(red) origin(black)

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e

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0 Blue 0

g

Green 21

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g

Green 21

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e

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Red 11

0 Blue 0

g

Green 21

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Muon

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t

t

’

g

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Mu_muid_truth_mothertype

:

v

e

- Red (-12)

0 Blue

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Mu_muid_truth_mothertype

:

v

e

- Red (-12)

0 Blue

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v

e

W’/W

2

+

H

0

/H

2

0

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MuonTruth_origin

:

V

e

Red (12)

0 Blue

W’/W

2

+

Green (34)

H

0

/H

2

0

Green (35)

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MuonTruth_origin

:

V

e

Red (12)

0 Blue

W’/W

2

+

Green (34)

H

0

/H

2

0

Green (35)

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μ+ μ-

Liza Sneitzer

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23

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El_truth_mothertype

:

Mu- Red (13)

0 Blue

-

V

e

Green (-12)

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El_truth_mothertype

:

Mu- Red (13)

0 Blue

-

V

e

Green (-12)

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El_truth_mothertype

:

Mu- Red (13)

0 Blue

-

V

e

Green (-12)

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El_truth_mothertype

:

Mu- Red (13)

0 Blue

-

V

e

Green (-12)

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Mu_muid_truth_mothertype

:

Mu- Red (13)

0 Blue

-

V

e

Green (-12)

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Mu_muid_truth_mothertype

:

Mu- Red (13)

0 Blue

-

V

e

Green (-12)

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MuonTruth_origin

:

V

e

Red (12)

0 Blue

W’/W

2

+

Green (34)

H

0

/H

2

0

Green (35)

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MuonTruth_origin

:

V

e

Red (12)

0 Blue

W’/W

2

+

Green (34)

H

0

/H

2

0

Green (35)