highlights of smu work + latest on monopole production at atlas

April 19, 2023April 19, 2023 11

Highlights of SMU Work + Latest on MonopoleHighlights of SMU Work + Latest on MonopoleProduction at ATLASProduction at ATLAS

Daniel Goldin

22 Daniel Goldin (SMU)Daniel Goldin (SMU)

Standard Model HiggsStandard Model Higgs

In Standard Model, Higgs boson(s) necessary as evidence of In Standard Model, Higgs boson(s) necessary as evidence of Higgs field. Higgs field responsible for giving masses to Higgs field. Higgs field responsible for giving masses to particles.particles.

LEP experiments LEP experiments excludedexcluded Higgs mass up to 114 GeV/c Higgs mass up to 114 GeV/c22 , , Tevatron (this year’s result) between 160 and 170 GeV/cTevatron (this year’s result) between 160 and 170 GeV/c22..

Higgs mass chosen in this work set at 170 GeV/cHiggs mass chosen in this work set at 170 GeV/c22..


Jets in Physics Signals: VBF H Jets in Physics Signals: VBF H → WW → l→ WW → ljj Processjj Process

H H → WW decay mode is → WW decay mode is one of main Higgs one of main Higgs discovery channels at LHC discovery channels at LHC and WW or ZZ fusion (VBF and WW or ZZ fusion (VBF fusion) is one of the main fusion) is one of the main modes of Higgs modes of Higgs production.production.

160GeV160GeV

BRBRBRBR

Might be possible to see a few signal Might be possible to see a few signal events early on (~10-100 pbevents early on (~10-100 pb-1-1).).

large BRlarge BR

mmH0H0[GeV][GeV] lljjjj (pb) (pb)

120120 0.180.18

140140 0.550.55

160160 0.850.85

180180 0.760.76

200200 0.530.53

VBF Higgs ProductionVBF Higgs Production

pW,Z

l

pW,Z

H

W

W

q

q

pW,Z

l

p

W,Z

HW

W

q

q

qq

qq

VBF jet

}}VBF jet

W jetsW jets

Higgs Branching RatiosHiggs Branching RatiosHiggs Branching RatiosHiggs Branching Ratios


Particle-Level Jets: W and VBF Jet EtaParticle-Level Jets: W and VBF Jet EtaParticle-Level Jets: W and VBF Jet EtaParticle-Level Jets: W and VBF Jet Eta

VBF JetsVBF Jets

W JetsW Jets

Jets in a Physics Signal:Jets in a Physics Signal: H H →→ WW WW through Vector Boson Fusionthrough Vector Boson Fusion

The H→WW → lThe H→WW → ljj channel has following advantages over fully leptonic H→WW → jj channel has following advantages over fully leptonic H→WW → llll:: Unlike lUnlike lll channel, missing E channel, missing ETT from only one neutrino in l from only one neutrino in lqq allows for Higgs qq allows for Higgs

mass determinationmass determination

Branching ratio for lBranching ratio for ljj is 5.5 times that of ljj is 5.5 times that of lll (with l = e (with l = e±±, , ± ± ))

Color coherence of the valence quarks → Color coherence of the valence quarks → jets from VBFjets from VBF process tend to be rather process tend to be rather forwardforward. Jets from the hadronically decaying W (. Jets from the hadronically decaying W (W jetsW jets) tend to be more ) tend to be more centralcentral..

However,However, mixing between VBF and W jets makes W mass (mixing between VBF and W jets makes W mass (⇒⇒Higgs Higgs massmass) determination ) determination challengingchallenging..


Jet Energy Scale (JES) from Hadronic WJet Energy Scale (JES) from Hadronic W

measjetpartabs

measjettotpart EKKE)L,R,,,E(KE

Absolute scale factor

Measured jet energyTrue jet energy

truejetpartpart E)L,R,E(KE

Parton-true jet

scale factor

For calibration with For calibration with physics channels at physics channels at ATLAS we can also ATLAS we can also

useuse

measjetabs

truejet E)L,,,E(KE

E = jet energyE = jet energy= = coordinate of the jet coordinate of the jet vertexvertex = detector resolution= detector resolutionR = cone sizeR = cone sizeL = luminosityL = luminosity

Parton energy

KKabsabsKKabsabs

KKpartpartKKpartpart}}}}Set to Set to

constant hereconstant hereSet to Set to

constant hereconstant here


Jet Energy Scale from VBF H→WW: “Pure” and Reconstructed W Jets Jet Energy Scale from VBF H→WW: “Pure” and Reconstructed W Jets

““Best case scenarioBest case scenario” of pure W jets and reco jets ” of pure W jets and reco jets matched to quarks:matched to quarks:

KKabsabs = = EEtruejettruejet//EEreco jetreco jet = 1.112 ± 0.007 = 1.112 ± 0.007

Pure W jets and quarks yield the parton scale KPure W jets and quarks yield the parton scale Kpart:part: : :

KKpartpart = = EEquarkquark//EEtrue jettrue jet = 1.029 ± 0.002 = 1.029 ± 0.002

Can determine the total JES by matching reconstructed Can determine the total JES by matching reconstructed jets to quarks:jets to quarks:

KKtottot = = EEquarkquark//EEreco jetreco jet = 1.109 ± 0.002 = 1.109 ± 0.002

Since these jets are of highest purity, the 3% deviation Since these jets are of highest purity, the 3% deviation from unity represents out-of-cone correction.from unity represents out-of-cone correction.

True Jet to Partons (KTrue Jet to Partons (Kpartpart))True Jet to Partons (KTrue Jet to Partons (Kpartpart))Reconstructed Jet to True Jet (KReconstructed Jet to True Jet (Kabsabs))Reconstructed Jet to True Jet (KReconstructed Jet to True Jet (Kabsabs))

Total Calibration Scale (KTotal Calibration Scale (Ktottot))Total Calibration Scale (KTotal Calibration Scale (Ktottot))

EEquarkquark/E/Erecoreco jetjet

EEtrue jettrue jet/E/Erecoreco jetjet EEquarkquark/E/Etruetrue jetjet


Jet Energy Scale from VBF H→WW: “Mixed” and Reconstructed W Jets Jet Energy Scale from VBF H→WW: “Mixed” and Reconstructed W Jets

Majority of jets from W are Majority of jets from W are mixedmixed and yield: and yield:

KKabsabs = = EEtrue jettrue jet//EEreco jetreco jet = 1.162 ± 0.002 = 1.162 ± 0.002

KKpartpart = = EEquarkquark//EEtrue jettrue jet = 0.965 ± 0.001 = 0.965 ± 0.001

KKtottot = = EEquarkquark//EEreco jetreco jet = 1.117 ± 0.002 = 1.117 ± 0.002

KKabsabs for mixed jets is 5% higher for mixed jets for mixed jets is 5% higher for mixed jets

than for pure jets. than for pure jets.

There is a 5% difference between KThere is a 5% difference between Kpartpart

between pure and mixed jets. Explained by between pure and mixed jets. Explained by

the contamination of mixed jets by particles the contamination of mixed jets by particles

from the interaction region.from the interaction region.Reconstructed Jet to True Jet (KReconstructed Jet to True Jet (Kabsabs)) True Jet to Partons (KTrue Jet to Partons (Kpartpart))True Jet to Partons (KTrue Jet to Partons (Kpartpart))

Total Calibration Scale (KTotal Calibration Scale (Ktottot))

KKtottot = E = Equarkquark/E/Erecoreco jetjet

EEtrue jettrue jet/E/Erecoreco jetjet EEquarkquark/E/Etruetrue jetjet


Jet Energy Scale from VBF H→WW: Summary

From values of KFrom values of Kpartpart conclude that Cone 0.7 algorithm is conclude that Cone 0.7 algorithm is adequate in describing hadronic W decays in VBF Hadequate in describing hadronic W decays in VBF H→→WW WW signal.signal.

From KFrom Kabsabs conclude that TowerJet method might not be most conclude that TowerJet method might not be most optimal for reconstructing jets in calorimeter. JES rising with optimal for reconstructing jets in calorimeter. JES rising with energy. Average Kenergy. Average Kabs abs > 1.> 1.

Possible improvement: TopoClusters. Possible improvement: TopoClusters.

April 19, 2023 9

VBF H→WW: Optimizing Jet Selection Cuts• VBF H→WW signal discovery potential and the potential cuts have been previously considered by the collaboration.VBF H→WW signal discovery potential and the potential cuts have been previously considered by the collaboration.• Among (quite a few) CSC jet cuts: Among (quite a few) CSC jet cuts:

– Select jets pSelect jets pTT > 30 GeV/c > 30 GeV/c

– 2 jets closest to PDG W mass are selected 2 jets closest to PDG W mass are selected → → W jet pairW jet pair candidates. Of the remaining jets select 2 jets with highest jet Pt’s candidates. Of the remaining jets select 2 jets with highest jet Pt’s →→ tag tag jetjet pair candidates. pair candidates.

– Require that the leading tag jet pRequire that the leading tag jet pTT > 50 GeV/c. > 50 GeV/c.

– Opposite hemisphere requirement: Opposite hemisphere requirement: j1j1××j2j2 < 0.< 0.

– Pseudorapidity separation: |Pseudorapidity separation: |j1j1--j2j2| < 4.4.| < 4.4.

– Invariant mass of pair of tag jets > 1500 GeV/cInvariant mass of pair of tag jets > 1500 GeV/c22..

– Central Jet Veto: no jets other than W jet pair with pCentral Jet Veto: no jets other than W jet pair with pTT > 30 GeV/c and | > 30 GeV/c and || < 3.2.| < 3.2.

– b jet vetob jet veto

– ……• We propose a new set of cuts that (ATLAS Note: ATLAS-COM-2008-168).We propose a new set of cuts that (ATLAS Note: ATLAS-COM-2008-168).

– improves the W jet candidate purityimproves the W jet candidate purity– no need to require (as the CSC note does) hadronic W be on mass shell. no need to require (as the CSC note does) hadronic W be on mass shell. – if W does happen to be on mass shell, the proposed selection should lead to less biased W mass if W does happen to be on mass shell, the proposed selection should lead to less biased W mass

determination. determination. – are likely to enhance signal-to-background ratio across most of background events.are likely to enhance signal-to-background ratio across most of background events.

• Considered signal and one of leading backgrounds: t-tbar…Considered signal and one of leading backgrounds: t-tbar…


Pt Balance CutPt Balance Cut

VBF HWW signal: VBF HWW signal: ppTT Balance Balance DistributionDistribution

t-tbar background: pt-tbar background: pTT Balance Distribution Balance Distribution

Cut pT < 25 GeV/cCut pT < 25 GeV/c Cut pT < 25 GeV/cCut pT < 25 GeV/c

Selection (5):pT balance cut

• Apply the pApply the pTT < 25 GeV/c < 25 GeV/c balance cut to improve W jet balance cut to improve W jet candidate selection. The cut candidate selection. The cut leaves leaves 29% signal and 2.7% 29% signal and 2.7% of the backgroundof the background events. events.

• ppTT balance: balance: 2 tag jet p 2 tag jet pTT’s + ’s + Higgs pHiggs pTT = = 2 tag jet p 2 tag jet pTT’s + ’s + p pT T

(l(lqq)qq)

VBF Higgs ProductionVBF Higgs Production

p

p

pW,Z

l

pW,Z

H

W

W

q

qW,ZW,Z

l

W,ZW,Z

HHWW

WW

q

q

qqqq

qq

VBF jet

}}VBF jet

W jetsW jets


Applying Results to Higgs MassApplying Results to Higgs Mass

Invariant Higgs Mass from 2 Reco Jets + Invariant Higgs Mass from 2 Reco Jets + Truth Leptons + Truth NeutrinoTruth Leptons + Truth Neutrino

Invariant Higgs Mass from 2 Reco Jets + Invariant Higgs Mass from 2 Reco Jets + Truth Leptons + Truth NeutrinoTruth Leptons + Truth Neutrino

Selection above, as opposed to taking jet pairs, whose invariant mass is closest to the PDG value, results in a higher purity W jets ⇒ more precise W mass determination ⇒ more precise Higgs mass determination.

Selection steps above lead to unbiased W mass estimate, not tied to previously measured value.

Invariant Mass of 2 W-Tagged JetsInvariant Mass of 2 W-Tagged JetsInvariant Mass of 2 W-Tagged JetsInvariant Mass of 2 W-Tagged Jets


Conclusions for HWW StudiesConclusions for HWW Studies

We have focused on the jet selection for the VBF H→WW →lqq signal and the ttbar background.

Estimated Jet Energy Scale for signal, i.e. how accurately physics events reconstructed in calorimeter. Cone algorithm with R = 0.7 describes parton events well. TowerJet reconstruction may be improved by considering TopoClusters

Presented a set of selection cuts, some of which have been proposed previously, while others were new. Combined selection should result in: improved significance of the VBF H→WW discovery. better purity (precision) of W mass determination.

Utilized custom-built package to assess effectiveness of W jet/tag jet separation of the signal. After cuts: factor of 37 reduction of background acceptance, with factor of 3.3 for signal.

To be done: Rest of backgrounds need to be obtained from real data. Cuts need to be optimized using multivariate analysis. Would like to look at jet-charge track association to improve purity of W

selection for VBF H→WW signal.

This work shelved for now by ATLAS until data comes in and we get better handle on W+jet and muiltijet backgrounds.


Dirac Monopole

2cn

eg

2cn

eg

Dngg Dngg eec

gD 5.682

eec

gD 5.682

Dirac Quantization Dirac Quantization Condition (1931)Condition (1931)

Dirac Quantization Dirac Quantization Condition (1931)Condition (1931)

Dirac Unit ChargeDirac Unit ChargeDirac Unit ChargeDirac Unit Charge

wherewherewherewhere

Searched, but not discovered, by many experiments, such as accelerators and cosmic detectors.

Theoretically:

Motivation:Motivation: Explains quantization of electric charges.Explains quantization of electric charges.

Symmetrization (Symmetrization (dualityduality) of Maxwell’s Equations: unit electric ) of Maxwell’s Equations: unit electric charge charge → unit magnetic charge.→ unit magnetic charge.

Predicted by GUT theories. Predicted by GUT theories.

Huge!Huge!Huge!Huge!


Monopole Production with Colliders

mm

p

p

Drell-Yan Diphoton Fusion throughelastic pp collision

mm

mm m

m

m

m

Already modeled for ATLAS at SMU (ATLAS int. note: Ana et al.)

Diphoton fusion has not yet been searched for at hadronic colliders. But calculated cross-sections already exist.

Elastic collisions easiest (fastest) to implement. Shown today. Semi-elastic and inelastic collisions also possible (to be done

later?), but generation more complex.

•Shown todayShown today•Shown todayShown today


Monopole Production Cross-Section through Elastic Diphoton FusionMonopole Production Cross-Section through Elastic Diphoton Fusion

Dz. Shoukavy et al., Mod. Phys. Lett. A Dz. Shoukavy et al., Mod. Phys. Lett. A 2121, 2873 , 2873 (2006) (2006) T.Dougall and S.D. Wick, Eur. Phys. J. A39, 213 T.Dougall and S.D. Wick, Eur. Phys. J. A39, 213 (2009)(2009)

Dz. Shoukavy et al., Mod. Phys. Lett. A Dz. Shoukavy et al., Mod. Phys. Lett. A 2121, 2873 , 2873 (2006) (2006) T.Dougall and S.D. Wick, Eur. Phys. J. A39, 213 T.Dougall and S.D. Wick, Eur. Phys. J. A39, 213 (2009)(2009)

M.Drees et al, Phys. Rev. D 50, 2335 (1994)M.Drees et al, Phys. Rev. D 50, 2335 (1994)

CompareCompareCompareCompare

(68.5 e)(68.5 e)22(68.5 e)(68.5 e)22

J.Schwinger et al., Annals Phys. 101, 451 (1976)K.Milton, Rept. Prog. Phys. 69, 1637 (2006)J.Schwinger et al., Annals Phys. 101, 451 (1976)K.Milton, Rept. Prog. Phys. 69, 1637 (2006)

Using duality and Rutherford scattering:Using duality and Rutherford scattering:Using duality and Rutherford scattering:Using duality and Rutherford scattering:

For n=1 (spin=1/2) monopole:For n=1 (spin=1/2) monopole:For n=1 (spin=1/2) monopole:For n=1 (spin=1/2) monopole:


MadGraph-Generated DiagramsMadGraph-Generated Diagrams

Cross-section Cross-section pp → mmpp → mm obtained using Weizsacker-Williams obtained using Weizsacker-Williams approximation (selectable in MadGraph): approximation (selectable in MadGraph):

photon distr. photon distr. inside protoninside protonphoton distr. photon distr. inside protoninside proton

)( mm

t-channelt = -2p2 (1 – cos)

u-channelu = -2p2 ( 1 + cos)


Monopole Cross-section vs. Mass from MadGraphMonopole Cross-section vs. Mass from MadGraph

Elastic diphotonElastic diphotonElastic diphotonElastic diphoton

Drell-YanDrell-YanDrell-YanDrell-Yan

Drell-Drell-YanYan

Drell-Drell-YanYan

Elastic Elastic diphotondiphotonElastic Elastic

diphotondiphoton

T.Dougall and S.D. Wick, Eur. Phys. J. A39, 213 T.Dougall and S.D. Wick, Eur. Phys. J. A39, 213 (2009)(2009)

T.Dougall and S.D. Wick, Eur. Phys. J. A39, 213 T.Dougall and S.D. Wick, Eur. Phys. J. A39, 213 (2009)(2009)

AgreementAgreement

X-section vs. Mass for massive leptons with regular QED couplings



Monopoles in Uniform Magnetic FieldMonopoles in Uniform Magnetic Field

Monopole’s trajectory in constant Monopole’s trajectory in constant magneticmagnetic field is like that of field is like that of electron in constant electron in constant electricelectric field (duality). field (duality).

In ATLAS BIn ATLAS Bzz (= 2 T), then equations of motion in (= 2 T), then equations of motion in r-zr-z plane: plane:

Lead to time-dependent trajectory:Lead to time-dependent trajectory:

Trajectory: catenary. Non-relativistic limit: parabola.Trajectory: catenary. Non-relativistic limit: parabola.


Monopole Energy LossMonopole Energy Loss

Adapt Bethe-Bloch energy loss to monopole (à la G. Bauer et al, Adapt Bethe-Bloch energy loss to monopole (à la G. Bauer et al, Nucl. Instrum. Meth. A 545, 503 (2005)):Nucl. Instrum. Meth. A 545, 503 (2005)):

neglect: neglect: ~10 ~10neglect: neglect: ~10 ~10

2

2

22222 2ln

21

Icm

AKZ

eng

dxdE e

duality: duality: z/z/→ng/e→ng/eduality: duality: z/z/→ng/e→ng/e

1111

I =I =I =I =

Thus, for monopole:Thus, for monopole:

S.P. Ahlen, Phys. Rev. D17, 17 (1978)S.P. Ahlen, Phys. Rev. D17, 17 (1978)

Note: more precise E-loss Note: more precise E-loss treatment (based on Ahlen) treatment (based on Ahlen) in our Drell-Yan int. note. in our Drell-Yan int. note.


Event Samples and SimulationEvent Samples and Simulation

Simulated 20k monopole events with MadGraph for MSimulated 20k monopole events with MadGraph for Mmonomono = = 400 GeV/c400 GeV/c22 and 1200 GeV/c and 1200 GeV/c22..

Rest of the simulation ROOT-based:Rest of the simulation ROOT-based: Simulated (roughly) detector volumes up to EM barrel calorimeter inner Simulated (roughly) detector volumes up to EM barrel calorimeter inner

wall.wall.

Propagated monopoles (anti-monopoles) using trajectory equations.Propagated monopoles (anti-monopoles) using trajectory equations.

If monopole traversed subdetector volume, energy loss was calculated, If monopole traversed subdetector volume, energy loss was calculated, and new kinematics were taken into account at exit of volume.and new kinematics were taken into account at exit of volume.

Assumptions: Assumptions: E-loss formula adapted from standard one, with exception of charge E-loss formula adapted from standard one, with exception of charge

replacement and ionization potential.replacement and ionization potential.

Only barrel and central tracking region simulated (Only barrel and central tracking region simulated ( < 1.4), no endcaps. < 1.4), no endcaps.

Detector volumes simulated as uniform “barrels” (no gaps, surface Detector volumes simulated as uniform “barrels” (no gaps, surface imperfections, etc.)imperfections, etc.)

Only the active materials simulated (e.g., for TRT: Xe gas, but no Only the active materials simulated (e.g., for TRT: Xe gas, but no polyamide tubing)polyamide tubing)

No support structures simulated.No support structures simulated.

B-field assumed uniform (2 T).B-field assumed uniform (2 T).


Energy Loss in Water: Implementation Cross-checkEnergy Loss in Water: Implementation Cross-checkd

E/d

x (

GeV

/cm

)

dE/d

x (

GeV

/cm

)


S.P. Ahlen, Phys. Rev. D17, 17 (1978)S.P. Ahlen, Phys. Rev. D17, 17 (1978)


Putting It All Together: Trajectory + ATLAS Geometry + ElossPutting It All Together: Trajectory + ATLAS Geometry + Eloss

Solenoid (Al)Solenoid (Al)Solenoid (Al)Solenoid (Al)

TRTTRT(Xe)(Xe)TRTTRT(Xe)(Xe)

Barrel EM calorimeterBarrel EM calorimeterBarrel EM calorimeterBarrel EM calorimeter

Tracker (Si)Tracker (Si)Tracker (Si)Tracker (Si)

Beam pipe (Be)Beam pipe (Be)Beam pipe (Be)Beam pipe (Be)

Sample 10 monopole tracks in ATLAS: mass = 400 GeV/c2

““low” |P| (= 318 GeV/c):low” |P| (= 318 GeV/c):mono trapped in solenoidmono trapped in solenoid

coilcoil

““low” |P| (= 318 GeV/c):low” |P| (= 318 GeV/c):mono trapped in solenoidmono trapped in solenoid

coilcoil

B = 2TB = 2TB = 2TB = 2T


Energy Losses in Detector VolumesEnergy Losses in Detector Volumes

Eloss in Si Tracker (Mmono = 400 GeV/c2) Eloss in Magnet (Mmono = 400 GeV/c2)

Eloss in Magnet (Mmono = 1200 GeV/c2)

Eloss in Si Tracker (Mmono = 1200 GeV/c2)


Acceptance Statistics (20k Events)Acceptance Statistics (20k Events)

beam

pip

ebeam

pip

ebeam

pip

ebeam

pip

e

magnet

magnet

magnet

magnet

beam

pip

ebeam

pip

ebeam

pip

ebeam

pip

e magnet

magnet

magnet

magnet

Si trackerSi trackerSi trackerSi tracker

TR

TTR

TTR

TTR

T

Si trackerSi trackerSi trackerSi tracker

TR

TTR

TTR

TTR

T

Monos Trapped in Det. Volumes (Mmono = 400 GeV/c2)

Monos Trapped in Det. Volumes (Mmono = 1200 GeV/c2)

Monos Out of Acceptance Region (Mmono = 400 GeV/c2)

Monos Out of Acceptance Region (Mmono= 1200 GeV/c2)


Acceptance Plots (MAcceptance Plots (Mmonomono = 400 GeV/c = 400 GeV/c22))

10k events10k events10k events10k events


Acceptance Plots (MAcceptance Plots (Mmonomono = 1200 GeV/c = 1200 GeV/c22))

1k events1k events1k events1k events


Monopole SummaryMonopole Summary

MMmonomonoppb)b) AcceptanceAcceptance Number of Number of

eventsevents

400 400 GeV/cGeV/c22 182.182.

0.249 ± 0.004 0.249 ± 0.004 (stat.)(stat.) 4.5E+044.5E+04

1200 1200 GeV/cGeV/c22 0.360.36 0.368 ± 0.003 0.368 ± 0.003

(stat.)(stat.) 133133

Monopole acceptances for 20k diphoton events with 1fb-

1 luminosity

We could get plenty of monopoles (if they exist)!We could get plenty of monopoles (if they exist)!We could get plenty of monopoles (if they exist)!We could get plenty of monopoles (if they exist)!


SummarySummary

Worked on a few topics while at SMU:Worked on a few topics while at SMU: Calorimeter calibrationCalorimeter calibration

Feasibility of producing Higgs in association with W,ZFeasibility of producing Higgs in association with W,Z

HH→→WW cut optimization and jet energy scaleWW cut optimization and jet energy scale

Jet energy scale with t-tbar eventsJet energy scale with t-tbar events

MonopolesMonopoles

Really enjoyed my time here, at SMU!Really enjoyed my time here, at SMU! Thanks very much to everybody I worked with! Thanks very much to everybody I worked with!


ExtrasExtras


Tower vs. TopoCluster JetsTower vs. TopoCluster Jets

Advantages of TopoCluster over Advantages of TopoCluster over Tower method:Tower method: Built-in noise suppressionBuilt-in noise suppression

Clusters can span more than one Clusters can span more than one area of calorimeter, even across area of calorimeter, even across gap regionsgap regions

e/he/h is corrected at detector level, is corrected at detector level, without use of specific jet without use of specific jet algorithmalgorithm

1

24

3

5

6

noise cells(no true signal)

noise cells(no true signal)

σσnois

enois

e (G

eV

) (

GeV

)

Tower jetsTower jets

Cluster jetsCluster jetsCluster jetsCluster jets

Tower jetsTower jets

n

ois

en

ois

e(G

eV

)(G

eV

)


Jet AlgorithmsJet Algorithms

Jet requirements:Jet requirements: Detector independenceDetector independence

Need for best possible Jet Energy Need for best possible Jet Energy Scale. Scale.

Infrared-safetyInfrared-safety: infrared instabilities : infrared instabilities undermine the claim of a jet algorithm to undermine the claim of a jet algorithm to be telling us about the short distance be telling us about the short distance physics.physics. Adding an arbitrarily soft gluon to the Adding an arbitrarily soft gluon to the

event should not change the jets.event should not change the jets.

Collinear safetyCollinear safety Appropriate EAppropriate ET T threshold must be threshold must be

chosen (case 1)chosen (case 1)

Case 2 taken care of by seedless Case 2 taken care of by seedless algorithm.algorithm.

infrared sensitivity(artificial split in absence of soft gluon radiation)

collinear sensitivity (1)(signal split into two towers below threshold)

collinear sensitivity (2)(sensitive to Et ordering of seeds)


Signal Events: W Jet Purity CutsSignal Events: W Jet Purity Cuts

Cut at number of constituents for the Cut at number of constituents for the mixed W jet: Nb. of constit. < 22.mixed W jet: Nb. of constit. < 22.

There is less correlation between inv. There is less correlation between inv. mass and fractional contamination as mass and fractional contamination as evidenced by slope of the 2D fit and evidenced by slope of the 2D fit and fewer number of high mass jets (M > fewer number of high mass jets (M > 100 GeV)100 GeV)

Peak’s mean shifted toward pure W jet Peak’s mean shifted toward pure W jet value. High mass tail is almost gone.value. High mass tail is almost gone.

For the reconstructed jets may be able For the reconstructed jets may be able to correlate the constituent cut with to correlate the constituent cut with the number of charged tracksthe number of charged tracks

Particle-Level Jets: W and VBF Jet Particle-Level Jets: W and VBF Jet EtaEta

Particle-Level Jets: W and VBF Jet Particle-Level Jets: W and VBF Jet EtaEta

Mixed W Jets Invariant Mixed W Jets Invariant Mass after Constituent CutMass after Constituent Cut

Mixed W Jets Invariant Mixed W Jets Invariant Mass after Constituent CutMass after Constituent Cut

Pure W Jets: Invariant MassPure W Jets: Invariant MassPure W Jets: Invariant MassPure W Jets: Invariant Mass

High mass tailHigh mass taildisappeareddisappeared

High mass tailHigh mass taildisappeareddisappeared

highlights of smu work + latest on monopole production at atlas

Documents

pure jets

reconstructed jets

true jet kabstrue jet

jet vertexs

etruejetereco jet

reco jets

reconstructing jets

contamination of mixed