Particle ID など - Osaka Universityosksn2.hep.sci.osaka-u.ac.jp/.../metro/lec_20131219_03.pdf2013/12/19 · the speciﬁc set of ghosts used, and change when the ghosts are modiﬁed

Particle ID など

同定すべきもの

Primary vertex電子，光子（EleMag object）ミューオンジェット‣ b-jet, τ-jetMissing ET‣ ニュートリノ，弱い相互作用程度以下の相互作用しかしない仮説上の粒子

2

Primary Vertex Selection

Hard scattered eventを選ぶ‣ VertexにassociateされたトラックのpT和で選別ジェットの選別で重要（後述）

3T

track p0 2 4 6 8 10 12 14 16 18 20

1

10

102

103

Min Bias

Primary vertex

Mean Number of Interactions per Crossing0 5 10 15 20 25 30 35 40 45

/0.1

]-1

Rec

orde

d Lu

min

osity

[pb

020406080

100120140160180 Online LuminosityATLAS

> = 20.7µ, <-1Ldt = 21.7 fb = 8 TeV, s

> = 9.1µ, <-1Ldt = 5.2 fb = 7 TeV, s

電子・光子の同定

EM object とハドロンの識別‣ カロリメータでシャワーの形状 ← X0<<λI๏ 縦方向：EMは前面でenergy deposit๏ 横方向：EMのほうが広がりが小さい⇒ どちら方向にもsegmentationが必要

‣ 飛跡検出器๏ 光子：EM objectに一致する飛跡がない๏ 電子 vs ハドロン✓電子はE/p=1

4

E: カロリメータでのエネルギーp: 飛跡検出器での運動量




4





4


EMエネルギーの較正

個々の検出器の反応を調整（inter-calibration）‣ J/ψなどからの電子最終的なスケールはZ→ee

ハドロニックジェットのスケールもEMエネルギースケールで決まる‣ γ+jetを使うので

5June 5, 2006 N. Buchanan CALOR 06 14

More on performance

• L1CAL vs precision readout agree well• good measure of L1CAL and cal readout

performance• new L1CAL for run IIB – expect similar agreement

Candidate mass (GeV)70 75 80 85 90 95 100 105 110

Ev

en

ts /

( 1

.6 G

eV

)

0

20

40

60

80

100

120

140

160

180

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220


Ev

en

ts /

( 1

.6 G

eV

)

0

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180

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Ev

en

ts /

( 1

.6 G

eV

)

0

20

40

60

80

100

120

140

160

180

200

220| < 0.2

phys!both electrons: |

| > 0.8phys

!both electrons: |

e e (both electrons in Central Cryostat)"Z

ミューオン

6

2 27. Passage of particles through matter

27.2. Electronic energy loss by heavy particles [1–22, 24–30, 82]

Moderately relativistic charged particles other than electrons lose energy in matterprimarily by ionization and atomic excitation. The mean rate of energy loss (or stoppingpower) is given by the Bethe-Bloch equation,

!dE

dx= Kz2 Z

A

1!2

!12

ln2mec2!2"2Tmax

I2 ! !2 ! #(!")2

". (27.1)

Here Tmax is the maximum kinetic energy which can be imparted to a free electron in asingle collision, and the other variables are defined in Table 27.1. With K as defined inTable 27.1 and A in g mol!1, the units are MeV g!1cm2.

In this form, the Bethe-Bloch equation describes the energy loss of pions in a materialsuch as copper to about 1% accuracy for energies between about 6 MeV and 6 GeV(momenta between about 40 MeV/c and 6 GeV/c). At lower energies various corrections

Muon momentum

1

10

100

Sto

ppin

g po

wer

[M

eV c

m2 /

g]

Lin

dhar

d-Sch

arff

Bethe-Bloch Radiative

Radiativeeffects

reach 1%

!" on Cu

Without !

Radiativelosses

"#0.001 0.01 0.1 1 10 100 1000 104 105 106

[MeV/c] [GeV/c]

1001010.1 100101 100101

[TeV/c]

Anderson-Ziegler

Nuclearlosses

Minimumionization

E!c

!$

Fig. 27.1: Stopping power (= "!dE/dx#) for positive muons in copperas a function of !" = p/Mc over nine orders of magnitude in momentum(12 orders of magnitude in kinetic energy). Solid curves indicate thetotal stopping power. Data below the break at !" $ 0.1 are taken fromICRU 49 [2], and data at higher energies are from Ref. 1. Verticalbands indicate boundaries between di!erent approximations discussedin the text. The short dotted lines labeled “µ! ” illustrate the “Barkase!ect,” the dependence of stopping power on projectile charge at very lowenergies [3].

August 29, 2007 11:19

ミューオン

6

2 27. Passage of particles through matter

27.2. Electronic energy loss by heavy particles [1–22, 24–30, 82]

Moderately relativistic charged particles other than electrons lose energy in matterprimarily by ionization and atomic excitation. The mean rate of energy loss (or stoppingpower) is given by the Bethe-Bloch equation,

!dE

dx= Kz2 Z

A

1!2

!12

ln2mec2!2"2Tmax

I2 ! !2 ! #(!")2

". (27.1)

Here Tmax is the maximum kinetic energy which can be imparted to a free electron in asingle collision, and the other variables are defined in Table 27.1. With K as defined inTable 27.1 and A in g mol!1, the units are MeV g!1cm2.

In this form, the Bethe-Bloch equation describes the energy loss of pions in a materialsuch as copper to about 1% accuracy for energies between about 6 MeV and 6 GeV(momenta between about 40 MeV/c and 6 GeV/c). At lower energies various corrections

Muon momentum

1

10

100

Sto

ppin

g po

wer

[M

eV c

m2 /

g]

Lin

dhar

d-Sch

arff

Bethe-Bloch Radiative

Radiativeeffects

reach 1%

!" on Cu

Without !

Radiativelosses

"#0.001 0.01 0.1 1 10 100 1000 104 105 106

[MeV/c] [GeV/c]

1001010.1 100101 100101

[TeV/c]

Anderson-Ziegler

Nuclearlosses

Minimumionization

E!c

!$

Fig. 27.1: Stopping power (= "!dE/dx#) for positive muons in copperas a function of !" = p/Mc over nine orders of magnitude in momentum(12 orders of magnitude in kinetic energy). Solid curves indicate thetotal stopping power. Data below the break at !" $ 0.1 are taken fromICRU 49 [2], and data at higher energies are from Ref. 1. Verticalbands indicate boundaries between di!erent approximations discussedin the text. The short dotted lines labeled “µ! ” illustrate the “Barkase!ect,” the dependence of stopping power on projectile charge at very lowenergies [3].

August 29, 2007 11:19

Radiativeでない領域（<O(1)TeV）‣ 十分な物質量（λI >10）を通過できるのはミューオン（とニュートリノ）だけ๏ 内部荷電飛跡検出器での飛跡と一致๏ バックグラウンド（π±，K±など）✓Punch through✓Decay• kinkを作るので，ビームの衝突地点から粒子が来ていることを要求

ジェット（１）

クォーク間のQCDポテンシャル

‣ クォークの閉じ込め‣ 生成されたクォークやグルーオンは，エネルギーに応じて多数のハドロン（＋崩壊による生成物）⇒ ジェット

7

V (r) ∼ −43

αs

r+ kr k ≅ 1013 GeV/cm

ジェット（２）

ジェットは定義依存：Algorithmとparameter‣ パートンまで戻しているかは解析に依る

8

JHEP04(2008)063

Figure 1: A sample parton-level event (generated with Herwig [8]), together with many randomsoft “ghosts”, clustered with four di!erent jets algorithms, illustrating the “active” catchment areasof the resulting hard jets. For kt and Cam/Aachen the detailed shapes are in part determined bythe specific set of ghosts used, and change when the ghosts are modified.

have more varied shapes. Finally with the anti-kt algorithm, the hard jets are all circular

with a radius R, and only the softer jets have more complex shapes. The pair of jets near

! = 5 and y = 2 provides an interesting example in this respect. The left-hand one is much

softer than the right-hand one. SISCone (and Cam/Aachen) place the boundary between

the jets roughly midway between them. Anti-kt instead generates a circular hard jet, which

clips a lens-shaped region out of the soft one, leaving behind a crescent.

The above properties of the anti-kt algorithm translate into concrete results for various

quantitative properties of jets, as we outline below.

2.2 Area-related properties

The most concrete context in which to quantitatively discuss the properties of jet bound-

aries for di!erent algorithms is in the calculation of jet areas.

Two definitions were given for jet areas in [4]: the passive area (a) which measures

a jet’s susceptibility to point-like radiation, and the active area (A) which measures its

susceptibility to di!use radiation. The simplest place to observe the impact of soft resilience

is in the passive area for a jet consisting of a hard particle p1 and a soft one p2, separated

– 4 –

ジェット（3）

Algorithm‣ cone๏ η-Φ平面で塊✓Rの大きさ✓seedの作り方

‣ kT๏ 運動量空間で塊‣ merge & split

9

Cone jetKT jet

R =�

η2 + φ2

dij = min(p2T,i, p

2T,j)∆R2

ij/D2

! !

!"#$%$&'()%#&*+(,"(-&*(./01*&$,"234&"()*&$5%"(%"'(3&,"6&$2(#,$1*(',17011&'(

8&*1(,"(&9&:(7;//,1,;"1<(*4&+(&5=4%1,>&'(*4%*(8&*(

7/01*&$,"2(501*(,5=/&5&"*(,"#$%$&'(1%#&*+(6+(

1055,"2(;?&$(1;#*(%"'(7;//,"&%$(7;"#,20$%*,;"1@

)*,//<(0"#;$&1&&"(=$;6/&51(7%"(%$,1&@((A4&(.BC(

D0":!(7;"&(%/2;$,*45(*0$"&'(;0*(*;(4%?&(%"(

,"#$%$&'(1&"1,*,?,*+(*4%*(E;0/'(%##&7*(

7%/70/%*,;"1(%*(FFGH(%"'(6&+;"'@

ジェットエネルギーの較正（1）

重要：ほとんどの解析で最大の系統誤差個々の粒子に対するカロリメータの応答ジェット全体に対する応答‣ 定義に依存することに注意‣ γ+jet あるいは Z+jet‣ 様々な補正๏ energy leakage✓shower, particles

๏ offset✓underlying events, multiple interactions

10

ジェットエネルギーの較正（2）

11

CHAPTER 5. EVENT RECONSTRUCTION 70

[GeV]ref

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Data 2011

Total uncertainty

ATLAS Preliminary

-1 L dt = 4.7 fb# = 7 TeV, s

R=0.4, EM+JEStanti-k

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Total uncertainty

ATLAS Preliminary

-1 L dt = 4.7 fb# = 7 TeV, s


(b) Anti-kt R = 0.6

Figure 7: Data-to-MC ratio of the mean pT balance as a function of prefT

for anti-kt jets with distance

parameter R = 0.4 (a) and R = 0.6 (b) calibrated with the EM+JES scheme. The total uncertainty on this

ratio is depicted by gray bands. Dashed lines show the !1%, !2%, and !5% shifts.

[GeV]ref

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ATLAS Preliminary

-1 L dt = 4.7 fb# = 7 TeV, s

R=0.4, LCW+JEStanti-k

(a) Anti-kt R = 0.4

[GeV]ref

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Total uncertainty

ATLAS Preliminary

-1 L dt = 4.7 fb# = 7 TeV, s

R=0.6, LCW+JEStanti-k

(b) Anti-kt R = 0.6

Figure 8: Data-to-MC ratio of the mean pT balance as a function of prefT

for anti-kt jets with distance

parameter R = 0.4 (a) and R = 0.6 (b) calibrated with the LCW+JES scheme. The total uncertainty on

this ratio is depicted by gray bands. Dashed lines show the !1%, !2%, and !5% shifts.

References

[1] M. Cacciari, G. P. Salam, and G. Soyez, The Anti-kt jet clustering algorithm, JHEP 04 (2008) 063,

arXiv:0802.1189 [hep-ph].

12

Figure 5.11: Data-to-MC ratio of the mean PT balance as a function of the PT of the Z bosonmeasured in the Z+jets analysis. Dashed lines show the !1%,!2% and !5% shifts [87].

the energy observed in data. Systematic uncertainties for JES are summarized in Figure 5.12and 5.13. The main source of the systematic uncertainties in the low energy region, belowPT " 30 GeV, is limited by the statistics of the Z events. Including this, the uncertainty isestimated to be approximately 2 % in total. For the high jet energy region, the main sourceof the systematic uncertainty comes from the photon and electron energy scale which wouldchange the reference momentum. The uncertainty is estimated by repeating the analysis byvarying photon or electron energy by ±1!. The di!erence from the nominal energy scale istaken as the systematic uncertainty, which is about 1 %.

[GeV]!

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0.04StatisticalPhoton energy scaleJet resolution

J2

TRadiation: p

,jet)!("#Radiation: MC generatorPhoton purityOut-of-coneTOTAL

ATLAS PreliminaryDB Method

= 7 TeVs-1 dt = 4.7 fbL$

jets, R = 0.4tanti-kEM+JES

| < 1.2det

%|

(a) R = 0.4, EM+JES

[GeV]!

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TRadiation: p



= 7 TeVs-1 dt = 4.7 fbL$

jets, R = 0.4tanti-kLCW+JES

| < 1.2det

%|

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%|

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= 7 TeVs-1 dt = 4.7 fbL$

jets, R = 0.6tanti-kLCW+JES

| < 1.2det

%|

(d) R = 0.6, LCW+JES

Figure 10: Systematic uncertainties on the ratio of the jet response in data over MC as determined by the

DB technique for anti-kt jets with R = 0.4 (a,b) and R = 0.6 (c,d), calibrated with the EM+JES scheme(a,c) and with the LCW+JES scheme (b,d), as a function of the photon transverse momentum.

16

Figure 5.12: Summary of the uncertainty for JES measured in the "+jets analysis [86]

The energy resolution in data is also measured with the similar method to measure JES.The width of the P jet

T /P !,ZT distribution can be considered as the jet energy resolution. The

resolution obtained with data is found to be consistent with the one in MC. No energy smearingagainst the jet energy in MC is applied.


[GeV]ref

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TotalStat.ExtrapolationsPile-up jet rejectionMC generatorsRadiation suppressionWidthOut-of-coneElectron energy scale

ATLAS Preliminary-1

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(a) Anti-kt R = 0.4

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ATLAS Preliminary-1

L dt = 4.7 fb! = 7 TeV, s


(b) Anti-kt R = 0.6

Figure 6: Summary of the uncertainties on the data-to-MC ratio of the mean pT balance, for anti-kt jets

with distance parameter R = 0.4 (a) and R = 0.6 (b) calibrated with the EM+JES scheme.

8 Results

Figure 7 shows the data-to-MC ratio of the mean pT balance for jets calibrated with the EM+JES scheme,

with statistical and systematic uncertainties. For R = 0.4 jets and prefT> 25 GeV, this ratio is shifted by

at most !4% from unity, and typically by !2% over most of the Z boson pT range. Uncertainties are

typically between 1% and 2% for 25 GeV < prefT< 260 GeV, and increase up to 10% for low transverse

momenta.

The corresponding results for the LCW+JES calibration are shown in Figure 8. They are qualitatively

similar to those of jets calibrated with the EM+JES scheme, except in the very first bin for R = 0.6 jets,

which is a!ected by large uncertainties.

9 Conclusion

Two jet energy calibration schemes have been probed using the direct pT balance between a central jet

and a Z boson. The data are from a 4.7fb!1 sample of proton-proton collisions at 7 TeV recorded by the

ATLAS detector. The responses measured in the data and in the simulation have been compared for jets

defined by the anti-kt clustering algorithm with distance parameters of R = 0.4 and R = 0.6. The data-

to-MC ratios, shown in Figures 7 and 8, are shifted by at most !8% from unity, and typically by !2% in

the range 45 GeV < prefT< 160 GeV, for both jet sizes and both calibration schemes. The uncertainty of

the method has been estimated to be between 1% and 2% for 30 GeV < prefT< 260 GeV. The results of

this study demonstrate that the direct pT balance technique provides a method that can be used to correct

the jet energies in situ.

Figure 5.13: Summary of the uncertainty for JES measured in the Z+jets analysis [87]

Selection

The definition of selected jets used in this analysis is described in this section. From recon-structed jets, a jet which is matched to the selected electron within the radius !R = 0.4 isremoved. PT of jets is required to be greater than 25 GeV. The absolute value of the pseudo-rapidity should be less than 2.5. For each jet, the jet vertex fraction (JVF) is computed as theparameter to judge if the jet is associated to PV. The JVF for a given Jeti is defined as

JVF(Jeti) ="kPT(TrkJeti

k , PV)"n"lPT(TrkJeti

l ,Vtxn), (5.3)

where PT(TrkJeti , Vtxn) is the momentum of the track which is matched to the Jeti within theradius !R = 0.4 and is associated to the n-th vertex. For a jet which falls outside of thefiducial region of the inner detector and a jet with no associated tracks, JVF = !1 is assigned.Figure 5.14 illustrates the event topology of interest described by Equation (5.3) for example.|JVF| is required to be greater than 0.75.

Reconstruction/JVF selection e!ciency

The jet reconstruction e#ciency is measured by using track-jets which are jets reconstructedfrom charged tracks [88]. The reconstruction e#ciency is defined as the ratio of the number ofthe reconstructed calorimeter-based jets to the track-jets. The observed reconstruction e#ciencyin data for a jet with high PT is almost consistent with MC. But a small ine#ciency, by "1 %,for jets below 30 GeV is observed in data. This is considered as a systematic uncertainty source.

The selection e#ciency based on the |JVF| > 0.75 requirement is measured using the Z #ee/µµ samples. To obtain the e#ciency for both hard-scattered jets and jets from the pile-upvertices called ‘pile-up jets’, the Z boson samples are divided into two categories based on PT

of the Z boson which is measured by the ee or µµ system. When the Z boson is boostedin the transverse direction, there should be a hard scattered jet in the opposite direction ofthe Z boson to conserve the transverse momentum, and vice versa. Therefore, to collect thehard-scattered jets, the Z boson is required to have PT greater than 30 GeV. In addition, the

Jet from Primary Vertex

そもそも（低エネルギー）ジェットは多い複数の衝突によるジェットのオーバーラップ‣ Primary vertexからのジェットを選びたい

12


1

JVF2 = 1-x (x>0)

pileup PV

JVF3 = 1JVF1 = 0

z-axis

Jet1

Jet2

Jet3

Figure 5.14: The schematic image of JVF. Jet1 is a jet originating from a pileup vertex. Jet2and Jet3 come from PV. Tracks from PV (the pileup vertex) are indicated in the blue (red)lines. JVF of Jet1 (JVF1) is zero because there is no matched tracks associated to PV. For Jet3,JVF equals to unity because all the associated tracks comes from PV. On the other hand, Jet2originally coming from PV have an associated track from the pileup vertex. Therefore, JVF2

should be smaller than unity.

jet in this Z boson event is required to be back-to-back against the Z boson. This selectiongives the sample of the hard-scattered jet with 2 % contamination of pile-up jets. On the otherhand, to collect the pile-up jet sample, the Z boson is required to have PT less than 10 GeV.The pile-up jet sample with 20 % contamination of hard-scattered jets can be obtained by thisselection. Using these two samples, the JVF selection e!ciency is measured and parametrizedas a function of jet PT as shown in Figure 5.15. A few percent higher e!ciency than MCexpectation is observed. To reproduce the e!ciency observed in data, MC events are scaledwith this scale factor. The uncertainty is evaluated by changing the reference jet selection forboth hard-scattered and pile-up jets. The typical size of the uncertainty is around 0.5 %.

5.6 Missing transverse energy

Missing transverse energy (EmissT ) is defined as the momentum imbalance on the plane transverse

to the beam direction. Such an imbalance implies a presence of the undetected particles such asneutrinos or other unknown stable and weakly-interacting particles. The momentum imbalanceis obtained from the negative vectorial sum of the momenta of all particles detected in theATLAS detector. The procedure of the Emiss

T reconstruction is summarized below and detailscan be found in [89].

EmissT is calculated from the reconstructed electrons, jets, soft-jets, and muons. Here, the jets

with the transverse momentum greater (less) than 20 GeV is categorized as ‘jets’ (‘soft-jets’).The lower energy jets are treated separately to use the robust EM scale energy calibrationinstead of the EM+JES energy calibration as for the higher energy jets. The x (y) componentsof the vector sum for each component are denoted as "Ee

x(y), "Ejetx(y), "Esoftjet

x(y) , and "Eµx(y),

respectively. To obtain "Eex(y) and "Eµ

x(y), electrons and muons which are reconstructed asexplained in Section 5.3 and 5.4 are used. Energy deposit in the calorimeter cells associated toelectrons and muons is removed from the calculation for other terms. For "Ejet

x(y) and "Esoftjetx(y) ,

the reconstructed jets as explained in Section 5.5 are used. In addition to these terms, the energydeposits which are not associated to any components above at the calorimeter is computed as


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ATLAS Preliminary-1

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(b) Anti-kt R = 0.6

Figure 6: Summary of the uncertainties on the data-to-MC ratio of the mean pT balance, for anti-kt jets

with distance parameter R = 0.4 (a) and R = 0.6 (b) calibrated with the EM+JES scheme.

8 Results

Figure 7 shows the data-to-MC ratio of the mean pT balance for jets calibrated with the EM+JES scheme,

with statistical and systematic uncertainties. For R = 0.4 jets and prefT> 25 GeV, this ratio is shifted by

at most !4% from unity, and typically by !2% over most of the Z boson pT range. Uncertainties are

typically between 1% and 2% for 25 GeV < prefT< 260 GeV, and increase up to 10% for low transverse

momenta.

The corresponding results for the LCW+JES calibration are shown in Figure 8. They are qualitatively

similar to those of jets calibrated with the EM+JES scheme, except in the very first bin for R = 0.6 jets,

which is a!ected by large uncertainties.

9 Conclusion

Two jet energy calibration schemes have been probed using the direct pT balance between a central jet

and a Z boson. The data are from a 4.7fb!1 sample of proton-proton collisions at 7 TeV recorded by the

ATLAS detector. The responses measured in the data and in the simulation have been compared for jets

defined by the anti-kt clustering algorithm with distance parameters of R = 0.4 and R = 0.6. The data-

to-MC ratios, shown in Figures 7 and 8, are shifted by at most !8% from unity, and typically by !2% in

the range 45 GeV < prefT< 160 GeV, for both jet sizes and both calibration schemes. The uncertainty of

the method has been estimated to be between 1% and 2% for 30 GeV < prefT< 260 GeV. The results of

this study demonstrate that the direct pT balance technique provides a method that can be used to correct

the jet energies in situ.

Figure 5.13: Summary of the uncertainty for JES measured in the Z+jets analysis [87]

Selection

The definition of selected jets used in this analysis is described in this section. From recon-structed jets, a jet which is matched to the selected electron within the radius !R = 0.4 isremoved. PT of jets is required to be greater than 25 GeV. The absolute value of the pseudo-rapidity should be less than 2.5. For each jet, the jet vertex fraction (JVF) is computed as theparameter to judge if the jet is associated to PV. The JVF for a given Jeti is defined as

JVF(Jeti) ="kPT(TrkJeti

k , PV)"n"lPT(TrkJeti

l ,Vtxn), (5.3)

where PT(TrkJeti , Vtxn) is the momentum of the track which is matched to the Jeti within theradius !R = 0.4 and is associated to the n-th vertex. For a jet which falls outside of thefiducial region of the inner detector and a jet with no associated tracks, JVF = !1 is assigned.Figure 5.14 illustrates the event topology of interest described by Equation (5.3) for example.|JVF| is required to be greater than 0.75.

Reconstruction/JVF selection e!ciency

The jet reconstruction e#ciency is measured by using track-jets which are jets reconstructedfrom charged tracks [88]. The reconstruction e#ciency is defined as the ratio of the number ofthe reconstructed calorimeter-based jets to the track-jets. The observed reconstruction e#ciencyin data for a jet with high PT is almost consistent with MC. But a small ine#ciency, by "1 %,for jets below 30 GeV is observed in data. This is considered as a systematic uncertainty source.

The selection e#ciency based on the |JVF| > 0.75 requirement is measured using the Z #ee/µµ samples. To obtain the e#ciency for both hard-scattered jets and jets from the pile-upvertices called ‘pile-up jets’, the Z boson samples are divided into two categories based on PT

of the Z boson which is measured by the ee or µµ system. When the Z boson is boostedin the transverse direction, there should be a hard scattered jet in the opposite direction ofthe Z boson to conserve the transverse momentum, and vice versa. Therefore, to collect thehard-scattered jets, the Z boson is required to have PT greater than 30 GeV. In addition, the

Missing ET

ビーム軸に垂直な平面上

‣ ハドロンコライダーではビーム軸方向の運動量は非保存　（なぜか？）定義が色々あるので注意‣ どのobjectを使うか‣ ジェットと認識されていないエネルギー

13

�ET = −�

i

−−→pT,i

ノイズとエネルギー較正に敏感

b-jet（1）

b-hadronは平均数ミリ飛んでから崩壊‣ 大きなインパクトパラメータ (d) を持つトラック‣ Secondary vertex の存在 (Lxy)Br(b→lX)~11% + Br(b→c→lX)~11% (l=e or μ)⇐ ジェット近傍のミューオン（あるいは電子）

14

bジェット

b-hadronからのトラック

d

Lxy

Primary Vertex

Secondary Vertex

b-jet（2）Impact parameter resolution が crucial ← Si！多くのalgorithmはlikelihood basis‣ d あるいは Lxy追加情報も使う‣ Secondary vertex 起源の粒子から不変質量など‣ V 粒子は不変質量から veto

15

March 10, 2008 – 10 : 22 DRAFT 13

Figure 5: Some distributions for good reconstructed two track vertices.a) - !+!! invariant mass spectrum with a peak of K0 decay;b) - p! invariant mass spectrum with a peak of " decay;c) - transverse plane distance between primary and secondary vertices with the peaks due to interactionsin beam pipe walls and pixel layers.

vertexing package.Tracks were selected with the same quality cuts as for the primary vertex reconstruction except for

the cut on transverse track impact parameter which was a0 " 3.5 mm.A search is started with a definition of all track pairs which form good (#2 < 3.5) 2-track vertices

inside jet. All results in this note were obtained with jets defined as a cone with size $R = 0.4 aroundprimary quarks (from Higgs decay) directions. Each track must have a 3D distance from primary vertex4)

divided by its error higher than 2.0 and sum of these two normalized distances for good track pair mustbe higher than 6.0.

Figure 6: Three dimensional distance between reconstructed primary and inclusive secondary verticesdivided by corresponding error for a) - light quarks jets and b) - b-quark jets.

Some of the reconstructed two track vertices are K0(") decays, % # e+e! conversions and hadronicinteractions in detector material. The corresponding distributions are presented in fig.5. The pictures 5a) and b) show !! and p! mass spectra for good 2 particle vertices with peaks due to K0 and " decays.The picture fig.5 c) shows a distance between primary and secondary vertices in the transverse planewith peaks due to interactions in the material of beam pipe and pixel layers. The tracks coming from

4)Distance in 3D space between reconstructed primary vertex and the point of closest approach of particle trajectory to thisvertex

b-jet（3）Efficiency 測定‣ e, μは Z やJ/ψ（あるいはW）が有用なcalibration source ← b にはない

‣ μ+jet や t-tbar (最近はこれがメインに)Fake rate 測定‣ negative tag rate

16b-jet efficiency

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Lig

ht je

t re

jection

1

10

210

310

410

IP2D

IP3D

IP3D+SV1

JetProb

IP3D+JetFitter

ATLAS

(a) Non-purified light jets

b-jet efficiency0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Lig

ht je

t re

jection

1

10

210

310

410

IP2D

IP3D

IP3D+SV1

JetProb

IP3D+JetFitter

ATLAS

(b) Purified light jets

b-jet efficiency0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

c-jet re

jection

1

10

IP2D

IP3D

IP3D+SV1

JetProb

IP3D+JetFitter

ATLAS

(c) c-jets

b-jet efficiency0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Tau-jet re

jection

1

10

210

IP2D

IP3D

IP3D+SV1

JetProb

IP3D+JetFitter

ATLAS

(d) !-jets

Figure 15: Rejection of light jets, c- and !-jets versus b-jet efficiency for t t̄ and tt̄ j j events and for alltagging algorithms: JetProb, IP2D, IP3D, IP3D+SV1, IP3D+JetFitter.

20

b-TAGGING – b-TAGGING PERFORMANCE

21

417

[GeV]T

jet p20 30 40 50 60 70 80 210 210×2 210×3

b-je

t effi

cien

cy s

cale

fact

or

0.6

0.8

1

1.2

PDF method (total error)PDF method (stat. error)

ATLAS Preliminary = 8 TeVs -1 L dt = 20.3 fb

= 70%bMV1,

MCdata/MCscale factor

τ-jet（1）BR(τ→lνν) ~35%, BR(τ→hadrons) ~65%‣ レプトニック崩壊はe,μを捕まえる‣ 今から話すのはハドロニック崩壊エネルギーの広がり具合の違い‣ q, g > τ > EM

17

3 / 9

trk,1f0 0.5 1 1.5 2

a.u.

0

0.05

0.1

0.15 jets (QCD)

) (Z

EMR0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

a.u

0

0.05

0.1

0.15 jets (QCD)

) (Z

アトラス実験におけるタウ粒子の同定

• タウ粒子は検出器到達以前に崩壊 (寿命10-13秒, c! = 87µm)"– レプトン化崩壊 (35%, !± → l±") "– ハドロン化崩壊 (65%, !± → #±") "

• タウ粒子の識別"– ジェットの太さ ( QCD > ! > e )"– 孤立して出易い (pT

leading track / pT! 大 )"

• light jet (u,d,s,c) > gluon, b の順で fake rate が大きい"

! QCD jet"

!

QCD" !" e$

1, 3本の"トラック"

ジェットの太さ" pTleading track / pT

! $

QCD jet"

!"#$%&'%(#")#*++%!"#$%&'%(#")#*++%

τ-jet（2）

粒子数　1prong, 3prong

18

Number of tracks0 1 2 3 4 5 6 7 8 9 10

Even

ts

0

5001000

15002000

2500

30003500

40004500

ATLAS Preliminary

After tau ID(Tight BDT working point)

)-1Data 2011 (4.6 fb) W (

) lW (µ/eJet background

Number of tracks0 2 4 6 8 10 12 14 16 18

Even

ts

0

2000

4000

6000

8000

10000

12000

ATLAS Preliminary

Before tau ID

)-1Data 2011 (4.6 fb) W (

) lW (µ/eJet background

Signal Efficiency0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Inve

rse

Back

grou

nd E

ffici

ency

1

10

210

310

410

TauBDT Summer 2012

TauBDT Winter 2013

1 Prong| < 2.5 > 15 GeV, |

Tp

= 8 TeVsData+Simulation 2012,

Preliminary ATLAS

シミュレーションなど

力の強さ

観測する力の強さは，対象とするエネルギーに依存する‣ 量子補正๏ ゲージボソンは不確定性原理の範囲内でvirtualstateになれる

๏ virtual stateでいられる時間がエネルギーに依存⇒ 力の強さが変化

20

Renormalization

QED

‣ 基準値として無限遠（Q→0）での値を０QCD

‣ Q→０で発散するので，基準値をとれない⇒ ”任意の”エネルギースケール(μ: renormalization scale)を基準値๏ 物理量が”任意の”スケールに依存

21

αS(Q2) =α(µ2)

1 + α(µ2) β04π ln(Q2

µ2 )

αeff (Q2) =α

1− α3π ln( Q2

m2e)

μ Dependence

22

Hard Interactions of Quarks and Gluons: a Primer for LHC Physics 27

Figure 16. The single jet inclusive distribution at ET = 100 GeV, appropriate forRun I of the Tevatron. Theoretical predictions are shown at LO (dotted magenta),NLO (dashed blue) and NNLO (red). Since the full NNLO calculation is not complete,three plausible possibilities are shown.

the moment the value of !2 is unknown (see Section 3.4). However, a range of predictions

based on plausible values that it could take are also shown in the figure, !2 = 0 (solid)and !2 = ±!2

1/!0 (dashed). It is clear that the renormalization scale dependence is

reduced when going from LO and NLO and will become smaller still at NNLO.

Although Figure 16 is representative of the situation found at NLO, the exact

details depend upon the kinematics of the process under study and on choices such as

the running of "S and the pdfs used. Of particular interest are the positions on the

NLO curve which correspond to often-used scale choices. Due to the structure of (36)there will normally be a peak in the NLO curve, around which the scale dependence

is minimized. The scale at which this peak occurs is often favoured as a choice. For

example, for inclusive jet production at the Tevatron, a scale of EjetT /2 is usually chosen.

This is near the peak of the NLO cross section for many kinematic regions. It is also

usually near the scale at which the LO and NLO curves cross, i.e. when the NLO

corrections do not change the LO cross section. Finally, a rather di!erent motivationcomes from the consideration of a “physical” scale for the process. For instance, in the

case of W production, one might think that a natural scale is the W mass. Clearly, these

three typical methods for choosing the scale at which cross sections should be calculated

do not in general agree. If they do, one may view it as a sign that the perturbative

expansion is well-behaved. If they do not agree then the range of predictions provided

by the di!erent choices can be ascribed to the “theoretical error” on the calculation.

3.3.3. The NLO K-factor The K-factor for a given process is a useful shorthand which

encapsulates the strength of the NLO corrections to the lowest order cross section. It iscalculated by simply taking the ratio of the NLO to the LO cross section. In principle,

inclusive jet

cross section NNLO

NLOLO


Table 1. K-factors for various processes at the Tevatron and the LHC calculated usinga selection of input parameters. In all cases, the CTEQ6M pdf set is used at NLO. Kuses the CTEQ6L1 set at leading order, whilst K! uses the same set, CTEQ6M, as atNLO. Jets satisfy the requirements pT > 15 GeV and |!| < 2.5 (5.0) at the Tevatron(LHC). In the W + 2 jet process the jets are separated by !R > 0.52, whilst the weakboson fusion (WBF) calculations are performed for a Higgs boson of mass 120 GeV.Both renormalization and factorization scales are equal to the scale indicated.

Typical scales Tevatron K-factor LHC K-factor

Process µ0 µ1 K(µ0) K(µ1) K!(µ0) K(µ0) K(µ1) K!(µ0)

W mW 2mW 1.33 1.31 1.21 1.15 1.05 1.15

W + 1 jet mW !pjetT " 1.42 1.20 1.43 1.21 1.32 1.42

W + 2 jets mW !pjetT " 1.16 0.91 1.29 0.89 0.88 1.10

tt̄ mt 2mt 1.08 1.31 1.24 1.40 1.59 1.48bb̄ mb 2mb 1.20 1.21 2.10 0.98 0.84 2.51

Higgs via WBF mH !pjetT " 1.07 0.97 1.07 1.23 1.34 1.09

the K-factor may be very di!erent for various kinematic regions of the same process.In practice, the K-factor often varies slowly and may be approximated as one number.

However, when referring to a given K-factor one must take care to consider the

cross section predictions that entered its calculation. For instance, the ratio can depend

quite strongly on the pdfs that were used in both the LO and NLO evaluations. It

is by now standard practice to use a NLO pdf (for instance, the CTEQ6M set) in

evaluating the NLO cross section and a LO pdf (such as CTEQ6L) in the lowest ordercalculation. Sometimes this is not the case, instead the same pdf set may be used for

both predictions. Of course, if one wants to estimate the NLO e!ects on a lowest order

cross section, one should take care to match the appropriate K-factor.

A further complication is caused by the fact that the K-factor can depend quite

strongly on the region of phase space that is being studied. The K-factor which is

appropriate for the total cross section of a given process may be quite di!erent from theone when stringent analysis cuts are applied. For processes in which basic cuts must

be applied in order to obtain a finite cross section, the K-factor again depends upon

the values of those cuts. Lastly, of course, as can be seen from Figure 16 the K-factor

depends very strongly upon the renormalization and factorization scales at which it is

evaluated. A K-factor can be less than, equal to, or greater than 1, depending on all of

the factors described above.As examples, in Table 1 we show the K-factors that have been obtained for a few

interesting processes at the Tevatron and the LHC. In each case the value of the K-

factor is compared at two often-used scale choices, where the scale indicated is used

for both renormalization and factorization scales. For comparison, we also note the K-

factor that is obtained when using the same (CTEQ6M) pdf set at leading order and at

NLO. In general, the di!erence when using CTEQ6L1 and CTEQ6M at leading orderis not great. However, for the case of bottom production, the combination of the large

K-factor≡σNLO/σLO

理論計算上の系統誤差の最大の要因

Factorization Scale

Q2<μF（factorization scale）はPDF‣ Q→０での発散を防ぐ‣ これも任意なので不定性の原因‣ 大抵は，renormalization scaleに揃える๏ Q2依存性はDGLAP方程式

23


treatment of certain hadronic cross sections. Studies were extended to other “hard

scattering” processes, for example the production of hadrons and photons with large

transverse momentum, with equally successful results. Problems, however, appeared to

arise when perturbative corrections from real and virtual gluon emission were calculated.

Large logarithms from gluons emitted collinear with the incoming quarks appeared to

spoil the convergence of the perturbative expansion. It was subsequently realized thatthese logarithms were the same as those that arise in deep inelastic scattering structure

function calculations, and could therefore be absorbed, via the DGLAP equations, in

the definition of the parton distributions, giving rise to logarithmic violations of scaling.

The key point was that all logarithms appearing in the Drell–Yan corrections could be

factored into renormalized parton distributions in this way, and factorization theorems

which showed that this was a general feature of hard scattering processes were derived [2].Taking into account the leading logarithm corrections, (1) simply becomes:

!AB =!

dxadxb fa/A(xa, Q2)fb/B(xb, Q

2) !̂ab!X . (2)

corresponding to the structure depicted in Figure 1. The Q2 that appears in the

parton distribution functions (pdfs) is a large momentum scale that characterizes

the hard scattering, e.g. M2l+l!, p2

T , ... . Changes to the Q2 scale of O(1), e.g.

Q2 = 2M2l+l!, M2

l+l!/2 are equivalent in this leading logarithm approximation.

Figure 1. Diagrammatic structure of a generic hard scattering process.

The final step in the theoretical development was the recognition that the finite

corrections left behind after the logarithms had been factored were not universal and

had to be calculated separately for each process, giving rise to perturbative O("nS)

corrections to the leading logarithm cross section of (2). Schematically

!AB =!

dxadxb fa/A(xa, µ2F ) fb/B(xb, µ

2F ) ! [ !̂0 + "S(µ2

R) !̂1 + ... ]ab!X . (3)

Here µF is the factorization scale, which can be thought of as the scale that separates

the long- and short-distance physics, and µR is the renormalization scale for the QCD

running coupling. Formally, the cross section calculated to all orders in perturbation

[2] Factorization (!")#$%&&'

Hard process(()*+ gg -> top top_bar scale Q

gluon,PDF : Q>!#'-./&scale012% PDF345

6$7189:;<=>?@ABC+

DEFG scale3HIJKL1M8

!'-./& scale,

?NO*P,collinearGQ!0RQ PDF3S$TU

!(factorization scale)VW-!X

PDF

実験からxの関数として求める理論計算上の系統誤差の要因‣ 特に，bやc

24

0

0.2

0.4

0.6

0.8

1

-410 -310 -210 -110 1

0

0.2

0.4

0.6

0.8

1

ZEUS-JETS PDF

)=0.1180Z(Ms!

uncorr. uncert.

total exp. uncert.

2 = 10 GeV2

Q

vxu

vxd

0.05)"xS (

0.05)"xg (

0

0.2

0.4

0.6

0.8

1

-410 -310 -210 -110 1

0

0.2

0.4

0.6

0.8

1

ZEUS-S PDF

0

0.2

0.4

0.6

0.8

1

-410 -310 -210 -110 1

0

0.2

0.4

0.6

0.8

1

MRST2001

0

0.2

0.4

0.6

0.8

1

-410 -310 -210 -110 1

0

0.2

0.4

0.6

0.8

1

CTEQ6.1M

0

0.2

0.4

0.6

0.8

1

ZEUS

x

xf

図 6: Q2 = 10 GeV2 における PDF分布をビヨルケン x

の関数として示す。xuv は価 uクォーク PDF、xdv は価dクォーク PDF、xgはグルーオン PDF、xSは海クォーク PDFである。同一図に収めるため、グルーオンと海クォークは 1/20にして表示してある。

• PDFの包括的な理解

– グルーオン分布と重いクォークの生成断面積– 高い x領域– フレーバー分解

• 前方ジェット生成、多ジェット終状態

以下の章では各々の課題についてその物理的意義や現状・最新結果などを述べる。

6.2 高いQ2での新相互作用の探索と陽子・縦偏極電子衝突による電弱相互作用の検証

高い Q2 では超短距離で電子とクォークが相互作用することになり、標準模型を越える物理が観測される可能性がある。また、観測されない場合でも、高い Q2 において摂動論的 QCD 、特に DGLAP 発展を詳細に検証することが非常に大切である。というのも、HERAで測定されたパートン分布関数を LHCで到達する超高 Q2 領域までDGLAP方程式で外挿する正当性を精密に検証する必要があるからである。図 7に、HERAおよび従来の固定標的型DIS実験、そして TEVATRONと LHCの運動学領域を (x,Q2)平面で示した。LHCの主な運動学的領域は、xでは 10!4 ! x ! 10!1 と HERAとほぼ同じ

x

Q2 /

GeV

2

Atlas and CMS

Atlas and CMS rapidity plateau

D0 Central+Fwd. Jets

CDF/D0 Central Jets

H1

ZEUS

NMC

BCDMS

E665

SLAC

10-1

1

10

102

103

104

105

106

107

108

10-7

10-6

10-5

10-4

10-3

10-2

10-1

1

図 7: HERAおよび固定標的型DIS実験とTEVATRON、LHCの運動学的領域。横軸はビヨルケン x、縦軸は Q2

である。LHC運動学的領域は、質量M の粒子がラピディティy に生成される際の素過程パートンの運動学領域として示してある。

であり、Q2では 104 ! Q2 ! 108 GeV2とHERAの最大Q2 領域と一部重なっている。HERA-Iでの DIS断面積測定では Q2 " 103 GeV2 でまだ統計誤差が系統誤差を上回っており (散乱断面積はプロパゲーター 1/Q4で落ちる)、LHC実験開始までに HERA-IIの高統計で最大 Q2

まで詳細に検証しておくことが肝要である。HERA-IIでは世界で初めて陽子と縦偏極電子の高エネルギー衝突が実現した。高い Q2 では電磁相互作用だけでなく電子と陽子の間にZ、W ボソンを交換する弱い相互作用の効果も入る。したがって、縦偏極電子ビームを用いることにより電弱相互作用の左右非対称性を直接に検証することが出来る。荷電流 DIS反応 ep ! !X はニュートリノ散乱の逆反

応であり、W ボソンを交換する純粋な弱い相互作用である。標準模型では弱い相互作用は V "A型、パリティは最大に破れているので右巻き荷電流の寄与はゼロとなり、散乱断面積は電子の縦偏極度の一次関数として

"P (e±p ! !X) = (1 ± P )"0 (2)

と書ける。P は縦偏極度、"P は縦偏極度 P の時の荷電流 DIS断面積、 "0 は無偏極の時の荷電流 DIS断面積である。荷電流DIS散乱の電子の縦偏極度依存性をみる解析は

HERA-IIの「目玉」であり運転開始以来、重点的に行わ

6

0

0.2

0.4

0.6

0.8

1

-410 -310 -210 -110 1

0

0.2

0.4

0.6

0.8

1

ZEUS-JETS PDF

)=0.1180Z(Ms!

uncorr. uncert.

total exp. uncert.

2 = 10 GeV2

Q

vxu

vxd

0.05)"xS (

0.05)"xg (

0

0.2

0.4

0.6

0.8

1

-410 -310 -210 -110 1

0

0.2

0.4

0.6

0.8

1

ZEUS-S PDF

0

0.2

0.4

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1

-410 -310 -210 -110 1

0

0.2

0.4

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0.8

1

MRST2001

0

0.2

0.4

0.6

0.8

1

-410 -310 -210 -110 1

0

0.2

0.4

0.6

0.8

1

CTEQ6.1M

0

0.2

0.4

0.6

0.8

1

ZEUS

x

xf

図 6: Q2 = 10 GeV2 における PDF分布をビヨルケン x

の関数として示す。xuv は価 uクォーク PDF、xdv は価dクォーク PDF、xgはグルーオン PDF、xSは海クォーク PDFである。同一図に収めるため、グルーオンと海クォークは 1/20にして表示してある。

• PDFの包括的な理解

– グルーオン分布と重いクォークの生成断面積– 高い x領域– フレーバー分解

• 前方ジェット生成、多ジェット終状態

以下の章では各々の課題についてその物理的意義や現状・最新結果などを述べる。

6.2 高いQ2での新相互作用の探索と陽子・縦偏極電子衝突による電弱相互作用の検証

高い Q2 では超短距離で電子とクォークが相互作用することになり、標準模型を越える物理が観測される可能性がある。また、観測されない場合でも、高い Q2 において摂動論的 QCD 、特に DGLAP 発展を詳細に検証することが非常に大切である。というのも、HERAで測定されたパートン分布関数を LHCで到達する超高 Q2 領域までDGLAP方程式で外挿する正当性を精密に検証する必要があるからである。図 7に、HERAおよび従来の固定標的型DIS実験、そして TEVATRONと LHCの運動学領域を (x,Q2)平面で示した。LHCの主な運動学的領域は、xでは 10!4 ! x ! 10!1 と HERAとほぼ同じ

x

Q2 /

GeV

2

Atlas and CMS

Atlas and CMS rapidity plateau

D0 Central+Fwd. Jets

CDF/D0 Central Jets

H1

ZEUS

NMC

BCDMS

E665

SLAC

10-1

1

10

102

103

104

105

106

107

108

10-7

10-6

10-5

10-4

10-3

10-2

10-1

1

図 7: HERAおよび固定標的型DIS実験とTEVATRON、LHCの運動学的領域。横軸はビヨルケン x、縦軸は Q2

である。LHC運動学的領域は、質量M の粒子がラピディティy に生成される際の素過程パートンの運動学領域として示してある。

であり、Q2では 104 ! Q2 ! 108 GeV2とHERAの最大Q2 領域と一部重なっている。HERA-Iでの DIS断面積測定では Q2 " 103 GeV2 でまだ統計誤差が系統誤差を上回っており (散乱断面積はプロパゲーター 1/Q4で落ちる)、LHC実験開始までに HERA-IIの高統計で最大 Q2

まで詳細に検証しておくことが肝要である。HERA-IIでは世界で初めて陽子と縦偏極電子の高エネルギー衝突が実現した。高い Q2 では電磁相互作用だけでなく電子と陽子の間にZ、W ボソンを交換する弱い相互作用の効果も入る。したがって、縦偏極電子ビームを用いることにより電弱相互作用の左右非対称性を直接に検証することが出来る。荷電流 DIS反応 ep ! !X はニュートリノ散乱の逆反

応であり、W ボソンを交換する純粋な弱い相互作用である。標準模型では弱い相互作用は V "A型、パリティは最大に破れているので右巻き荷電流の寄与はゼロとなり、散乱断面積は電子の縦偏極度の一次関数として

"P (e±p ! !X) = (1 ± P )"0 (2)

と書ける。P は縦偏極度、"P は縦偏極度 P の時の荷電流 DIS断面積、 "0 は無偏極の時の荷電流 DIS断面積である。荷電流DIS散乱の電子の縦偏極度依存性をみる解析は

HERA-IIの「目玉」であり運転開始以来、重点的に行わ

6

PDFの測定（の一例）

LHCはpp衝突なので，u-barとd-barの寄与が等しいと仮定すると，W+とW-の生成断面積の違いはuとdのPDFの違い

25

pp/p

ug

W+

d

c s

Resonance decays: correlated with hard subprocess

[nb]+W

5.5 6 6.5 7

[nb]

-W

3.5

4

4.5

= 7 TeV)sData 2010 (MSTW08HERAABKM09JR09

total uncertaintyuncorr. exp. + stat.uncertainty

-1 L dt = 33-36 pb

ATLAS Preliminary

[nb]+W

5.5 6 6.5 7

[nb]

-W

3.5

4

4.5

モンテカルロシミュレーション

信号，バックグラウンドのアクセプタンス（検出効率を含む）の評価

26

N = σ × L× acceptance測定測定

知りたい

• 粒子種• 粒子の分布• 検出器のcoverage• 検出器の検出効率

シミュレーションの流れ

LOあるいはNLOでのmatrix elementの計算‣ PDFが必要生成されたパートンのシャワーパートンシャワー → ハドロン生成検出器シミュレーション

各段階で様々なシミュレーター (組み合わせ)

27

粒子の種類と分布

検出できるかどうか

測定精度

系統誤差とバイアス‣ シミュレーションが現実を再現しているか

28

N = σ × L× acceptance統計誤差系統誤差

Paolo Meridiani

VERY GOOD UNDERSTANDING OF PHYSICS OBJECTS

4

Multiple Interactions 依存性

29

Number of reconstructed primary vertices0 2 4 6 8 10 12 14 16 18 20

Elec

tron

iden

tifica

tion

effic

ienc

y [%

]

60

65

70

75

80

85

90

95

100

105ATLAS Preliminary -1 4.7 fb Ldt Data 2011

2012 selection criteriaData Loose++MC Loose++

Data Medium++MC Medium++

Data Tight++MC Tight++

ミューオン電子

バンチあたり衝突数再構成されたpp衝突地点数

Efficiencyやresolutionがバンチあたり衝突数に依存しているかどうか

Multiple Interactions 依存性

30

Documents

Particle ID など - Osaka Universityosksn2.hep.sci.osaka-u.ac.jp/.../metro/lec_20131219_03.pdf2013/12/19 · the speciﬁc set of ghosts used, and change when the ghosts are modiﬁed