Daniel Froidevaux Fest, November 2019 · 2019-12-01 · 1997: M. Dittmar and H. Dreiner, H à WW à ℓℓ νν as the dominant search mode at the LHC from m H = 150 – 180 GeV,

Daniel Froidevaux

ATLAS in the Making:

TDR and Physics Expectations

2Daniel Froidevaux Fest, November 2019


Daniel Froidevaux

The UA2 Collaboration (1985, Heidelberg)


Lydia Iconomidou-Fayard

Kevin Einsweiler Peter Jenni

Daniel Froidevaux

Louis Fayard

Pierre Darriulat

Peter Hansen Karlheinz Meier

The UA2 Collaboration (1985, Heidelberg)

Neville Harnew

Livio Mapelli

Karl Jakobs

Jean-Paul Repellin

Jean-Marc Gaillard

Gilles Sauvage


Daniel as an Authority on LHC Physics

HewasoneofthekeyexperimentalphysicistswhoshapedboththephysicsattheLHCandthelayoutoftheexperiments,designedtorunatluminositiesof1034cm-2s-1

-  PresentatallconferencesandimportantworkshopsonLHCphysics,oftenasconvenerofimportantsessions

-  Highlyrespectedbytheoristsasanexperimentalreference

-  InitiatingmoredetailedMonteCarlosimulationstudies(inthesocalledDICEframework)tounderstandthesignalandbackgroundconditions

-  Initialfocusoncalorimetercoverage..andofcourserightfromtheearlydayshewasalreadyinterestedintheInnerDetectorlayout,whichwasheavilydiscussed.

-  Asexpected,Daniel‘sinterestwasonthekeyquestion:rejectionofjetsfakingelectrons!Inaddition,therewasanaffinitytoaTransitionRadiationDetector,whichatalaterstage,becameaTransitionRadiationTracker


Daniels look into the future ~1990


A major milestone: Aachen 1990


The first serious studies


The first serious studies

“None ot the other possible channel provides any hope to discover a Higgs boson in this mass range.”

H à ZZ* àℓℓ ℓℓ H à γγ


“Daniel,genero

usasalways,h

adsharedapr

eviewofhisAa

chen

slideswithme,andt

hoseslideswer

ethefirstclear

pathwayIsaw

towardstheHi

ggsdiscovery2

2yearslater.”

A few quotes from people working closely with Daniel

CharacterizingDaniel:-  Terriblybrightandwithaveryfastmind-  Exceptionallanguageskills,e.g.forRussian,DolgosheindescribedDaniel’sskillsas“onecouldhearthatheisprobablynotfromMoscow”-  Waswellonhiswaytobecomeanastronaut,orrathercosmonautsincehefollowedtheRussianprocedure-  Veryproductive-  Verypleasantandhelpful-  Anintellectualfighterthatdoesnotgivein-  Honestandclearwithwhathethinks


Daniel as ATLAS “Physics Coordinator” (since ever – ~2000) 25 May 1999

Daniel announcing the approval of the LHC in Dec 94


The Early Days in the Early 90s


The Early Days in the Early 90s

Working with Daniel close to important deadlines: “...onecouldnevercatchupworkingwithDaniel,inparticularnotbeforesubmissionofimportantpapers/TDRs,whenheworkedthroughdaysandnightswithoutsleep.‘‘ (Partially)confirmed:Preparationof“lastminuteslides”ofHiggsworkinggroupforAachen1990inthenightbeforeat4amwithDaniel:“Ineededsomesleep,20minminimum,alarmclockset”;Daniel:“Notimetosleep,Icontinueworking”“Iwokeuponehourlater(didnothearthealarm)andfoundDanielsleeping,faceonthedesk”


How B Physics came to ATLAS

Evian meeting March 1992: “There were plans shown for several b-physics experiments (COBEX, GAJET and LHB), focusing on the measurement of sin2β with B0 -> J/Ψ K0, and I thought that we should be able to see this channel with a general purpose experiment as well, if we had a reasonable vertex detector (for the B), tracker (for the K0), and a trigger for sufficiently low-pT muons.” “Daniel and Peter Jenni were carefully supportive, but doubted the idea in the beginning. Anyway, Daniel helped me to get started with some simple simulations. I think that he was specially interested in the opportunities of the TRT for the K0

s reconstruction (to strengthen the physics case for the TRT), while he was more careful with the sin2β measurement capabilities. à  First publications, joint by Nick Ellis and others: P.Eerola, N.Ellis, D.Froidevaux and S.Weinzierl, Reconstruction of B0

d -> J/Ψ K0 decays in the ATLAS Experiment at LHC, Proceedings of Snowmass, Colorado, June 21–July 2, 1993. S. Gadomski, P.Eerola, N.Ellis and D.Froidevaux, Reconstruction of B0

d -> π+π- decays in the ATLAS Experiment at LHC, Proceedings of Snowmass, Colorado, June 21–July 2, 1993.

“These early years were important specially to widen the ATLAS physics potential and to put ambitious efforts on the vertexing (B layer) and the low-pT trigger. Daniel had an essential role in understanding this potential early on, supporting the early studies through his own involvement, and giving his as-always critical comments.”


b-tagging in ATLAS


b-tagging in ATLAS


Physics workshop in the US (1994)

The “core” Physics Group in 1994 Daniel Froidevaux, Andreas Dell’Acqua, Giacomo Polesello, Fabiola Gianotti, Luc Poggioli and Elzbieta Richter-Was (taking photo)


Physics Simulations


Troublemaker: Inner Detector


Troublemaker: Inner Detector


The exploration of the MSSM

Pioneering work by theorists: e.g. Z. Kunszt, F. Zwirner, Nucl. Phys. B385 (1992) 3, in addition to work done for SSC studies (Gunion et al.)

Important contributors: Elzbieta Richter-Was, Fabiola Gianotti, Donatella Cavalli, Luc Poggioli, Silvia Resconi





4 Higgs observable 3 Higgs observable 2 Higgs observable 1 Higgs observable h,A,H,H±

h,A,H,H±

Assuming decays to SM particles only

h,H±

h (SM -like)

h,H±

h,A,H

H,H±

h,H,H±

h,H

5σ contours

Here only SM-like h observable if SUSY particles neglected.

“ThereisnoholeattheLHC”



4 Higgs observable 3 Higgs observable 2 Higgs observable 1 Higgs observable h,A,H,H±

h,A,H,H±

Assuming decays to SM particles only

h,H±

h (SM -like)

h,H±

h,A,H

H,H±

h,H,H±

h,H

5σ contours

Here only SM-like h observable if SUSY particles neglected.

“ThereisnoholeattheLHC”

ATLAS 300 fb-1

Higgs decays via SUSY particles

If SUSY exists : search for H/A → χ0

2χ02 → ℓℓχ0

1 ℓℓχ01

5σ contours ATLAS: SUGRA scan m0 = 50 - 250 GeV m1/2 = 100 - 300 GeV tan β = 1.5 - 50 A 0 = 0


“Wealwaysdiscussedphysic

s...Danielwasalwaysfullofgreatide

as,which

wereopeninghorizons

andkeptmebusy.Alwaysencou

raging,inspiring,

positive,curious,sm

ilingandjoking.Ine

vergotboredeveni

fIhadtoredo

workafewtimesbecauseitwasnotyet

perfect.”

“...wheneverw

edisagreedonphys

ics,whichwedidsometimes,hewas

saying"proofittom

e”.Sometimesittookmeweeks,but

whenIwas

correctheaccepted

.”

... more quotes from people working closely with Daniel

“Danielwasanexcellentsupervisor:dynamic,multi-taskingand

funny.Ilearnedalotwithhim.Hewassopowerful:Irememberthe

frequentsituationwherearound8pmafter12h*)ofworkinghewas

cominginmyofficetostartstudyingmyresultsandlookatthedata

foranotherthreehours.”*)strongunderstatement

Danielintroducedmetothenotionof‘shortcut’!

Whenyourunoutoftime(launchingjobsat3

am

fora9ammeeting),gototheessential:apply

crudedetectorsmearing“byhand”.

Somanytimesusefulinmylife!


The first ATLAS Physics Workshop, Trest 1995


An “Invariant” at CERN over the past 30 years


The mSUGRA enterprise (1995 / 1996) - Another milestone: the 1996 LHCC SUSY Workshop -

Important contributors: Giacomo Polesello, Frank Paige, Elzbieta Richter-Was, Fabiola Gianotti, Ian Hinchliffe, Marjorie Shapiro, Luc Poggioli, J. Söderquist, ...


Sensitivity on parameters in point 1:


ATLFAST

All these studies –as well as all the MSSM studies – would not have been possible without another project inspired by Daniel, ”ATLFAST" which served us from the Technical Proposal (94) to the Physics TDR (99) … and then for almost another decade, rewritten to OO/C++


The Physics TDR (1997 - 1999) A major step in the understanding of the ATLAS Physics Potential

Top: Marina Cobal, John Parsons B-Physics: Paula Eerola, Nick Ellis Higgs: Karl Jakobs, Elzbieta Richter-Was SUSY: Giacomo Polesello, Ian Hinchliffe Exotics: Excursion: HowdidonebecomeHiggsconveneratTDRtimes?


The Physics TDR

Major Issues: -  H à bb decays? via WH, ZH, ttH production - H à WW Post TDR issues: -  Comparison to Tevatron -  Vector Boson Fusion


H à bb

√s =2 TeV

WZ WH WZ WH

√s =14 TeV

mH = 120 GeV, 30 fb-1

Backgrounds (tt, Wjj, Wbb, WZ): -- large and with different shapes -- not all well known today (missing K-factors) -- not all can be measured precisely with data → large background systematics in this channel and S/B ~ few %

→ considered as marginal discovery channel at the LHC

ZH → ℓℓ bb, ZH → ννbb have smaller sensitivity and/or even higher backgrounds → hopeless

WH production


The H à WW channel 1997: M. Dittmar and H. Dreiner, H à WW à ℓℓ νν as the dominant search mode at the LHC from mH = 150 – 180 GeV, Phys. Rev. D55 (1997) 167 1999: H à WW*à ℓℓ νν established in the Physics TDR 2014: ATLAS Run-1 paper on H à WW: Observation and measurement of Higgs boson decays to WW* with the ATLAS detector, Phys. Rev. D92 (2015) 012006

0

200

400

600

800

50 100 150 200 250 300

0

50

100

150

0

stat ± Obssyst ± Bkg

HiggsWWMisidVVTopDY

Bkg - Obssyst ± Bkg

Higgs

(b) Background-subtracted

[GeV]TmEv

ents

/ 10

GeV

µµee/+µe, 1≤jn(a)

Even

ts /

10 G

eV

ATLAS-1fb 20.3 TeV, =8 s

-1fb 4.5 TeV, =7 s

WW*→H

InbetweenDanielhada“RoadtoDamascus”experience1999:Greatsceptic2014:Greatestadvocat,EditorialBoardChairoftheRun-1legacypaper2015:AdvocattouseHàWWchannelfornormalizationincouplingmeasurements


The pleasure of working in Daniel’s team


The pleasure of working in Daniel’s team (cont.)


Vector Boson Fusion at low mass Proposed by D. Rainwater and D. Zeppenfeld et al. (hep-ph/9712271, hep-ph/9808468, hep-ph/9906218)


“I have always been impressed by his sharp intelligence and his capacity to

listen to hours of talks, understand everything and spot any weakness.

Also the fact that he had always pushed for the best precision in all details of

performance of the detector and insisted on the importance that everything

should be done in the best possible way. Only with that approach can we

obtain such an incredible precision out of this complex detector.

This was also very important to motivate generations of students and

postdocs that passed through ATLAS in the last 25 years to work in

performance as an indispensable ingredient. And of course the same is true

for physics analysis. I believe that Daniel is one of the persons that had a

large influence in the way physics is done in ATLAS with a great attention to

detail, carefulness in estimating uncertainties and producing sound high

quality results and papers.”

... more quotes from people working closely with Daniel


Daniel, we will miss you!! - As an authority

-  For your critical mind and for your physics judgment -  For your invaluable comments in meetings and for your (tons of) comments on CDS -  For your inspiring conversations, and (sometimes) provocative statements -  ... and for many other things.


Despite you are looking into other directions now (as well), I am sure, you will never forget ATLAS It was a great privilege to work with you, ... thanks for everything, ... and enjoy the free time!

Great thanks for recollection of the 1990s to: Elzbieta Richter-Was, Giacomo Polesello, Luc Poggioli, Donatella Cavalli, Martine Bosmann, Marina Cobal, Torsten Akesson, Johann Collot, Anatoli Romaniouk, Paula Eerola, Lydia Iconomidou-Fayard,...

Documents

Daniel Froidevaux Fest, November 2019 · 2019-12-01 · 1997: M. Dittmar and H. Dreiner, H à WW à ℓℓ νν as the dominant search mode at the LHC from m H = 150 – 180 GeV,