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Potential for searches & measurements: an overview for discussion. Jonathan Butterworth UCL Boosted Boson Workshop, CERN 25/3/2014. Potential for searches & measurements: “I apologise in advance”. Jonathan Butterworth UCL Boosted Boson Workshop, CERN. The core issue….

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Potential for searches measurements an overview for discussion
Potential for searches & measurements:an overview for discussion

Jonathan Butterworth

UCL

Boosted Boson Workshop,

CERN

25/3/2014

Jon Butterworth, UCL


Potential for searches measurements i apologise in advance
Potential for searches & measurements:“I apologise in advance”

Jonathan Butterworth

UCL

Boosted Boson Workshop,

CERN

Jon Butterworth, UCL


The core issue
The core issue…

  • Final stage of jet structure is “soft” non-perturbative QCD.

    • Formation of hadrons from gluons, 100 MeV energy scales (LQCD)

  • Vast phase space between quark-gluon scatter (100’s GeV, few TeV) and LQCD

  • Most of jet substructure can be analysedperturbatively

  • EWSB scale (~100 GeV) lies in this region

    • Jets may contain objects with EW-scale mass (W,Z,H,t,?)

Jon Butterworth, UCL


Standard model topologies
Standard Model Topologies

  • Dibosons; especially WW/WZ/ZZ - inclusive and vector boson fusion/scattering.

    • Inclusive: high pTtail is where anomalous couplings might show up

    • VBS: Unitarity test of BEH mechanism at high diboson mass. High diboson masses  high boosts (2002, JMB, Cox, Forshawand others; recently Cui & Han 2014 (Schwartz 2011)).

  • In both case, low statistics at most interesting area – recover hadronic decays of the bosons


Standard model topologies1
Standard Model Topologies

  • Top/tt

    • High pT tail… understand efficiencies for differential cross section measurement.

    • Main power is in Higgs & BSM searches (?)


Standard model topologies2
Standard Model Topologies

  • Higgs …

    • H WW or ZZ decays (the “original” channel, Seymour 1994) . Boost will not come from Higgs mass. However there will be phase space where there are boosted (off-shell) hadronic decays of Ws and Zs. Any chance?

    • VH(H bb) (the “classic” channel? BDRS 2008) High pTis the most sensitive region in Run I. Higher boosts in Run II likely to require jet substructure.


High p t higgs and vector boson reprise
High pT Higgs and Vector Boson (reprise)

“mono”-Jet

  • By requiring that the Higgs and Vector Boson have a high transverse momentum, we lose a factor of ~20 in cross section

    • However, much of this would have failed other analysis cuts anyway

    • Background cross sections fall by a bigger factor (typically t-channel not s-channel)

  • W/Z and H are all central

    • Better b-tagging, better jet resolution

  • W/Z and H decay products collimated

    • Simpler topology, fewer combinatorials

    • Difficult for tops to fake this

  • Z  neutrinos becomes visible

    • High missing ET

mH

b

H

W

u

l

Jon Butterworth, UCL


High p t higgs and vector boson reprise1
High pT Higgs and Vector Boson (reprise)

  • Note excellent Z peak for calibration

  • 5.9 s; potentially very competitive

  • bb branching information critical for extracting Higgs properties

    • “Measuring the Higgs sector” Lafaye, Plehn, Rauch, Zerwas, Duhrssen, arXiv:0904.3866 [hep-ph]

Jon Butterworth, UCL


High p t higgs and vector boson reprise2
High pT Higgs and Vector Boson (reprise)

  • Pre-data!

  • Included trigger, ATLAS b-tagging algorithm, detailed tracking & calorimeter

  • Also include Wt background omitted from initial study.

  • Slight degradation w.r.t particle level, but still very promising

Jon Butterworth, UCL


Standard model topologies3
Standard Model Topologies

  • Higgs …

    • gg H (Hbb) and others.

      • Can we recover Hbb without the V tag?

      • Can we tag the hadronic V decays too?


Standard model topologies4
Standard Model Topologies

  • Higgs …

    • gg H (Hbb) and others.

      • Can we recover Hbb without the V tag?

      • Can we tag the hadronic V decays too?

    • ttH (Plehn, Salam, Spannowsky 2010) boost of top of Higgs can be useful and needs to be dealt with.


Standard model topologies5
Standard Model Topologies

  • Combine techniques for top and Higgs tagging to improve sensitivity to Higgs in ttH channel

Jon Butterworth, UCL


Standard model topologies6
Standard Model Topologies

  • Higgs …

    • Hgg … I know we’re concentrating on hadrons, but… isolation cone merging… similar issues and technologies?


Bsm topologies all of the above
BSM Topologies (all of the above?)

  • Especially top: Enhanced BSM production at high pT in many models

    • Kaluza-Klein graviton (Lillie, Randall, Wang, 2007)

    • t’ (Holdom, 2007)

    • + SUSY stuff…




Bsm topologies all of the above1
BSM Topologies (all of the above?)

  • We have new boson to boost… HH (Kribs, Martin, Roy, Spannowsky, 2009; Cooper, Konstantinidis, Lambourne, Wardrope, 2013; ATLAS-CONF-2014-005)


Bsm topologies all of the above2
BSM Topologies (all of the above?)

  • We have new boson to boost… HH (Kribs, Martin, Roy, Spannowsky, 2009; Cooper, Konstantinidis, Lambourne, Wardrope, 2013; ATLAS-CONF-2014-005)


Bsm topologies all of the above3
BSM Topologies (all of the above?)

  • SUSY cascades to W,Z,H (JMB, Ellis, Raklev 2007) top (Han, Katz, Son, Tweedie, 2012)

    • Scuffles over mass hierarchies/naturalness &c…

    • Models (e.g. CP violating) with low limits on hadronically decaying Higgs partners (Bhattacherjee, Chakraborty, Ghosh, Raychaudhuri, 2012)


Bsm topologies all of the above4
BSM Topologies (all of the above?)

  • R-Parity Violating SUSY (As above + Salam 2009, and more)

  • from talk by Minho Son


Bsm topologies all of the above5
BSM Topologies (all of the above?)

  • …?

  • … Integrated into dijet/multijet searches?


Techniques
Techniques

  • Improve mass resolution

    • Dealing with pile-up, UE and soft radiation

  • Identifying decays

    • Suppressing (hard) QCD background



MANY MORE SINCE

MANY MORE SINCE

Jon Butterworth, UCL



Splitting and filtering bdrs and atlas
Splitting and filtering (BDRS) and ATLAS

Jon Butterworth, UCL


Filtering trimming and pruning cms
Filtering, Trimming and PruningCMS

Jon Butterworth, UCL


Shower deconstruction s oper spannowsky and atlas conf 2014 003
Shower deconstruction (Soper & Spannowsky) and ATLAS-CONF-2014-003

Jon Butterworth, UCL


Split filter is an example of doing both
Split/filter is an example of doing both

  • Start with Higgs candidate jet (highest pT jet in acceptance) with mass m)

  • Undo last stage of clustering (reduce radius to R12)

    J  J1, J2

  • If max(m1,m2) < 2m/3

    Call this a “mass drop”. This fixes the optimal radius for reconstructing the Higgs decay. Keep the jet J and call it the Higgs candidate.

    Else, go back to 2

  • Require Y12 > 0.09

    Dimensionless rejection of asymmetric QCD splitting

    Else reject the event

  • Require J1, J2 to each contain a b-tag

    Else reject the event

Jon Butterworth, UCL


Split filter is an example of doing both1
Split/filter is an example of doing both

  • Define Rfilt = min(0.3, Rbb/2)

    Make use event-by-event of the known Higgs decay radius

    Angular ordering means this is the characteristic radius of QCD radiation from Higgs products

    Stuff outside of this is likely to be underlying event and pileup.

  • Recluster, with Cambridge/Aachen, R = Rfilt

  • Take the 3 hardest subjets and combine to be the Higgs

    b, anti-b and leading order final state gluon radiation

  • Plot the mass

Jon Butterworth, UCL


Improved subjet analysis
Improved subjet analysis

Jon Butterworth, UCL


Improved subjet analysis1
Improved subjet analysis

Jon Butterworth, UCL


Improved subjet analysis2
Improved subjet analysis

Jon Butterworth, UCL


Improved subjet analysis3
Improved subjet analysis

Jon Butterworth, UCL


Improved subjet analysis4
Improved subjet analysis

Jon Butterworth, UCL


Improved subjet analysis5
Improved subjet analysis

Jon Butterworth, UCL


Learned since
Learned since…

  • y cut more powerful than mass drop (identifying decay. QCD suppression rather than UE/pile up.)

  • Filtering, uses Higgs decay angle to optimise the zoom on “hard physics”/suppression of soft stuff. Other techniques also available, some more generic (n-subjettiness, shower deconstruction). Competition in this channel?

  • Dijet R = 0.4 anti kT does a pretty good job (at least at 8 TeV).


Precision jets at the highest scales
Precision jets at the highest scales

  • Highest transverse momentum jets; at the TeVscale


Jets at the highest scales
Jets at the highest scales

  • General agreement with NLO QCD calculations (after soft corrections)

  • Can comparisons be made more (or less?) precise if groomed jets are used?

Significant spread in “NLO” predictions. ME/PS matching? MC tune (UE)? PDFs?


Vector bosons and b jets
Vector bosons and (b) jets

arXiv:1304.7098

arxiv:1302:2929


Limiting factors b tagging g bb
Limiting factors – b-tagging & gbb

  • CMS b/anti-b correlations

  • arXiv:1102.3194, JHEP 1103 (2011) 136

Princeton, J.Butterworth


Limiting factors b tagging g bb1
Limiting factors – b-tagging & gbb

  • Bottom &/or charm production introduces another hard (or “semi-hard”) scale. How well is this understood?

arXiv:1210.0441

Jon Butterworth, HCP


Limiting factors b tagging g bb2
Limiting factors – b-tagging & gbb

  • B jet (and dijet) cross sections compared to NLO QCD

arXiv:1109.6833 arXiv:1202.4617

Jon Butterworth, HCP


Limiting factors b tagging g bb3
Limiting factors – b-tagging & gbb

  • B jet (and dijet) cross sections compared to NLO QCD

arXiv:1109.6833 arXiv:1202.4617

Jon Butterworth, HCP


Limiting factors b tagging g bb4
Limiting factors – b-tagging & gbb

  • B jet (and dijet) cross sections compared to NLO QCD

arXiv:1109.6833 arXiv:1202.4617

Jon Butterworth, HCP


Limiting factors b tagging g bb5
Limiting factors – b-tagging & gbb

Good agreement with POWHEG, poorer with [email protected] (seen by both ATLAS & CMS)

arXiv:1109.6833 arXiv:1202.4617

Jon Butterworth, HCP


Limiting factors b tagging g bb6
Limiting factors – b-tagging & gbb

  • Use properties of displaced decay vertices to distinguish light, c and b jets in dijet events

arXiv:1210.0441

Jon Butterworth, HCP


Jet grooming and subjets
Jet grooming and subjets

arXiv:1203.4606


Jet grooming and subjets1
Jet grooming and subjets

  • kT scale, N-subjettiness

arXiv:1203.4606


Shower deconstruction
Shower deconstruction

Jon Butterworth, UCL


Shower deconstruction1
Shower deconstruction

Jon Butterworth, UCL


Shower deconstruction2
Shower deconstruction

Jon Butterworth, UCL


Shower deconstruction3
Shower deconstruction

Jon Butterworth, UCL


Shower deconstruction4
Shower deconstruction

Jon Butterworth, UCL


Shower deconstruction5
Shower deconstruction

Jon Butterworth, UCL


Shower deconstruction6
Shower deconstruction

Jon Butterworth, UCL


Shower deconstruction7
Shower deconstruction

Jon Butterworth, UCL


Substructure in searches
Substructure in searches

Jon Butterworth, UCL


… also

  • Jet shapes, Q-jets, jet charge, jet pull, jet superstructure…

  • Moving on from the “two goals” (tagging & grooming) to finding still more information; identifying jet properties in context, learning more about the short-distance physics.

Jon Butterworth, UCL


Subjets and measuring boosted objects
Subjets and measuring boosted objects

  • Gone from wacky new idea to obviously essential item in the toolkit (~6 years)

  • Studies with data show:

    • modelling is adequate but can be improved in some cases

    • “Grooming” is generally robust against pile up and important for controlling it in all jet measurements

  • Not seen full potential yet in Higgs searches … will become essential in more places at14 TeV

Jon Butterworth, UCL


Subjets and measuring boosted objects1
Subjets and measuring boosted objects

  • Already widely used in searches (mainly boosted tops, but more results on HH, W/Z coming…)

  • Calibration work on of novel observables is intense & interesting

  • Theoretical work on developing (analytic?) understanding

  • Boost meetings 2009 Stanford 2010 Oxford 2011 Princeton 2012 Valencia 2013 Arizona 2014 UCL (18-22 August, www.hep.ucl.ac.uk/boost2014)

Jon Butterworth, UCL


Backup
Backup

Jon Butterworth, UCL


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