The Cannon and the Camera

How and Why to go Beyond the Discovery of the Higgs Boson

John Alison University of Chicago

http://hep.uchicago.edu/~johnda/ComptonLectures.html Lecture Outline

April 1st: Newton’s dream & 20th Century Revolution April 8th: Mission Barely Possible: QM + SR April 15th: The Standard Model April 22nd: Importance of the Higgs April 29th: Guest Lecture May 6th: The Cannon and the Camera May 13th: The Discovery of the Higgs Boson May 20th: Problems with the Standard Model May 27th: Memorial Day: No Lecture June 3rd: Going beyond the Higgs: What comes next ?

2 Reminder: The Standard Model

Description fundamental constituents of Universe and their interactions Triumph of the 20th century Quantum Field Theory: Combines principles of Q.M. & Relativity

Constituents (Matter Particles) Spin = 1/2 Leptons: Quarks:

νe νµ ντ u c t ( e ) ( µ) ( τ ) ( d ) ( s ) (b ) Interactions Dictated by principles of symmetry Spin = 1 QFT ⇒ Particle associated w/each interaction (Force Carriers) γ W Z g

3 Reminder: The Standard Model

Description fundamental constituents of Universe and their interactions Triumph of the 20th century Quantum Field Theory: Combines principles of Q.M. & Relativity

Constituents (Matter Particles) Spin = 1/2 Leptons: Quarks:

νe νµ ντ u c t ( e ) ( µ) ( τ ) ( d ) ( s ) (b ) Interactions Dictated by principles of symmetry Spin = 1 QFT ⇒ Particle associated w/each interaction (Force Carriers) γ W Z g Consistent theory of electromagnetic, weak and strong forces ...... provided massless Matter and Force Carriers

4 Reminder: The Standard Model

Description fundamental constituents of Universe and their interactions Triumph of the 20th century Quantum Field Theory: Combines principles of Q.M. & Relativity

Constituents (Matter Particles) Spin = 1/2 Leptons: Quarks:

New field (Higgs Field) added to the theory Allows massive particles while preserve mathematical consistency Works using trick: “Spontaneously Symmetry Breaking”

Zero Field value Symmetric in Potential Energy not minimum Field value of Higgs Field Ground State

0 Higgs Field Value Ground state (vacuum of Universe) filled will Higgs field Leads to particle masses: Energy cost to displace Higgs Field / E=mc Additional particle predicted by the theory: 2 Generally Expected / Needed for Logical Consistency! Higgs boson: H Spin = 0 6 Last Time: The Higgs Boson

What do we know about the Higgs Particle: A Lot Higgs is excitations of v-condensate ⇒ Couples to matter / W/Z just like v X

matter: e µ τ / quarks W/Z

h h ~ (mass of matter) ~ (mass of W or Z)

matter W/Z

Spin: 0 1/2 1 3/2 2

Only thing we don’t (didn’t!) know is the value of mH

7 History of Prediction and Discovery

Late 60s: Standard Model takes modern form. Predicts massive W/Z bosons 1983: W/Z discovered at CERN:

8 History of Prediction and Discovery

Late 60s: Standard Model takes modern form. Predicts massive W/Z bosons 1983: W/Z discovered at CERN: u e u ν Z W

u e d e

9 History of Prediction and Discovery

Late 60s: Standard Model takes modern form. Predicts massive W/Z bosons 1983: W/Z discovered at CERN: u e u ν Z W

u e d e Early 90s: W/Z used to predict top mass t t Z Z W W t b

10 History of Prediction and Discovery

Late 60s: Standard Model takes modern form. Predicts massive W/Z bosons 1983: W/Z discovered at CERN: u e u ν Z W

u e d e Early 90s: W/Z used to predict top mass t t Z Z W W t b 1995: top quark discovered at fermilab 2000s: W/top quark and used to predict the higgs:

11 History of Prediction and Discovery

Late 60s: Standard Model takes modern form. Predicts massive W/Z bosons 1983: W/Z discovered at CERN: u e u ν Z W

u e d e Early 90s: W/Z used to predict top mass t t Z Z W W t b 1995: top quark discovered at fermilab 2000s: W/top quark and used to predict the higgs:

12 History of Prediction and Discovery

Late 60s: Standard Model takes modern form. Predicts massive W/Z bosons 1983: W/Z discovered at CERN: u e u ν Z W

u e d e Early 90s: W/Z used to predict top mass t t Z Z W W t b 1995: top quark discovered at fermilab 2000s: W/top quark and used to predict the higgs:

13 History of Prediction and Discovery

Late 60s: Standard Model takes modern form. Predicts massive W/Z bosons 1983: W/Z discovered at CERN: u e u ν Z W

u e d e Early 90s: W/Z used to predict top mass t t Z Z W W t b 1995: top quark discovered at fermilab 2000s: W/top quark and used to predict the higgs: h h t t W W

14 History of Prediction and Discovery

Late 60s: Standard Model takes modern form. Predicts massive W/Z bosons 1983: W/Z discovered at CERN: u e u ν Z W

u e d e Early 90s: W/Z used to predict top mass t t Z Z W W t b 1995: top quark discovered at fermilab 2000s: W/top quark and used to predict the higgs: h h t t W W 50 < mH < 150 GeV (95%) 15 History of Prediction and Discovery

Late 60s: Standard Model takes modern form. Predicts massive W/Z bosons 1983: W/Z discovered at CERN: u e u ν Z W

u d Now introduced basic theory.e e Early 90s: W/Z used to predict Switch top gears mass discuss what it takes to test it. t t Z Z W W t b 1995: top quark discovered at fermilab 2000s: W/top quark and used to predict the higgs: h h t t W W 50 < mH < 150 GeV (95%) 16 Today’s Lecture

The Cannon and the Camera

17 Particle Physics for 3rd Graders

18 Everything Molecules Atoms

No Body Knows Protons Quarks ? u What’s in the Lunch Box ? What’s in the Lunch Box ?

Look inside.

No Fun! What’s in the Lunch Box ? SMASH THEM!!!

Bang! What’s in the Lunch Box ?

Bang! What’s in the Proton ? Protons are Too small to look inside. What’s in the Proton ? Protons are Too small to look inside.

SMASH THEM!!!

Bang! The Worlds Biggest Cannon

CERN Switzerland/France

Philadelphia The Worlds Biggest Cannon The Worlds Biggest Cannon

Philadelphia The Worlds Biggest Cannon Really Big Camera!!! Really Big Camera!!! Really Big Camera!!! Really Big Camera!!! 3. Reconstruction and Commissioning 20

Figure 3.2: Event display of a tt¯ di-lepton candidate in the eµ-channel with two b-tagged jets. The electron is shown by the green track pointing to a calorimeter cluster, the muon by the long red track miss intersecting the muon chambers, and the ET direction is indicated by the blue dotted line in the x-y view. The secondary vertecies of the two b-tagged jets are indicated by the orange ellipses in the upper right. 3rd Grade Explanation is Essentially Correct

Some Caveats: - More sophisticated analog to “what are quarks made of ?” - What comes out of the lunch box is there to begin with…

However, basic concepts/methods something that anyone understands One of the great things about this business !

Rest of lecture: - Refine basic notions of camera and cannon - Discuss challenges in collecting/analyzing pictures - Talk about how we use picture to compare to test SM 3rd Grade Explanation is Essentially Correct

Some Caveats: - More sophisticated analog to “what are quarks made of ?” - What comes out of the lunch box is there to begin with…

However, basic concepts/methods something that anyone understands One of the great things about this business !

Some Caveats: - More sophisticated analog to “what are quarks made of ?” - What comes out of the lunch box is there to begin with…

However, basic concepts/methods something that anyone understands One of the great things about this business !

Rest of lecture: - Refine basic notions of camera and cannon - Discuss challenges in collecting/analyzing pictures - Talk about how we use picture to test SM 3. The ATLAS ExperimentA Toroidal LHC ApparatuS 17

Figure 3.1: Cut-away view of the ATLAS detector. 38

signed to measure the energy of electrons, photons, and hadrons. They are sensitive to both charged and neutral particles. The Muon Spectrometer (MS) surrounds the calorimeters. All particles except muons and neu- trinos are stopped by the calorimeter system. The MS is designed to measure the trajectories of muons leaving the calorimeter. The MS is composed of muon chambers operating in a magnetic field, provided by the toroid magnetics. A common coordinate system is used throughout ATLAS. The interaction point is defined as the origin of the coordinate system. The z-axis runs along the beam line. The x-y plane is perpendicular to the beam line, and is referred to as the transverse plane. The positive x-axis points from the interaction point to the center of the LHC ring; the positive y-axis points upward to the surface of the earth. The detector half at positive z-values is referred to as the “A-side”, the other half the “C-side”. The transverse plane is often described in terms of r-⇤ coordinates. The azimuthal angle ⇤ is measured from the x-axis, around the beam. The radial dimension, r, measures the distance from the beam line. The polar angle ⇥ is defined as the angle from the positive z-axis. The polar angle is often reported in terms of pseudorapidity, defined as = ln tan(⇥/2). The distance R is defined Not reviewed, for internal circulation only 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 td ftesi fteHgslk atcei the in particle Higgs-like the of spin the of Study hne ih2. fb 20.7 with channel ⇤ erdcino hsatceo at fi salwda pcfidi h CB-. license. CC-BY-3.0 the in specified as allowed is it of parts or article this of Reproduction c rdcinfato agrta 5 o pn2pril,ada 1 ofiec ee fone if level confidence 91% a at assumes and one particle, if spin-2 level pure a confidence assumes for 95% 25% at and than signal signal, larger spin-2 spin-0 fraction the a production a of favours in exclusion detector excess ATLAS the the observed in with results the 2012 of in collected compatibility Data the disfavours charge-parity. the on which on photons, reports two constraint note to This only mode decay the 125 hypothesis. observed Presently, about the spin-1 the of from a unknown. mass of stems a particle are rate this with properties production of boson physics measured spin Higgs other The Model its Standard boson. the but GeV, Higgs with consistent Model is Standard particle the new for search the in H oyih 03CR o h eeto h TA Collaboration. ATLAS the of benefit the for CERN 2013 Copyright The Basic Outputs: ⌅ eety h TA olbrto eotdteosraino e eta particle neutral new a of observation the reported collaboration ATLAS the Recently, Inner Tracking WW ( ⇥ ) System ⌅ Text Text gg production. e A lot goes into ofwork making/understanding these basic outputs. ⇥ µ ⇥ erhaiigfo ihrasi- rasi- atcewt positive with particle spin-2 a or spin-0 a either from arising search 1 of h TA Collaboration ATLAS The TA NOTE ATLAS ⇧ s eray2,2013 26, February = detector Abstract 8 e aacletdwt h ATLAS the with collected data TeV Electro-Magnetic Calorimeter H ! WW ( ⇤ rf eso 1.0 version Draft ) q ! q ⌅ e ⌫ X µ ⌫ Calorimeter Hadronic Muon Muon Tracking System ν ν ν e µ τ u c t e µ τ d s b

40 ν ν ν e µ τ u c t e µ τ d s b

41 ν ν ν e µ τ u c t e µ τ d s b

42 ν ν ν e µ τ u c t e µ τ d s b

43 ν ν ν e µ τ u c t e µ τ d s b

44 ν ν ν e µ τ u c t e µ τ d s b

45 ν ν ν e µ τ u c t e µ τ d s b

46 + +

ν ν ν e µ τ u c t e µ τ d s b

47 + + g γ W Z

48 Higgs decays

H → bb: ~60% H → WW: ~20%

+ + +

H → ττ: ~5% H → ZZ: ~2% H → γγ: 0.2%

+ + + + + +

49 3. Reconstruction and Commissioning 20

Jet (b-tag) Muon

MeT

Jet (b-tag)

Electron

51 b-jet Identification (b-Tagging)

Critical as b-jet ubiquitous in Higgs final states.

b-jet Displaced Tracks

Secondary Vertex

Jet Lxy

d0 InteractionPrimary Vertex Point

Jet

1 b-jet Identification (b-Tagging)

Critical as b-jet ubiquitous in Higgs final states.

b-jet Displaced - b-lifetimes ~pico-seconds Tracks - Typical speed (time dilation) ⇒ travel O(mm) Secondary Vertex ~mm Jet Lxy

d0 InteractionPrimary Vertex Point

Jet

1 b-jet Identification (b-Tagging)

Critical as b-jet ubiquitous in Higgs final states.

b-jet Displaced - b-lifetimes ~pico-seconds Tracks - Typical speed (time dilation) ⇒ travel O(mm) Secondary Vertex ~mm Jet Lxy ~10 µm

d0 InteractionPrimary Drives specs. on detector resolution Vertex Point (Must know detector positions to ~µm)

Jet

1 b-jet Identification (b-Tagging)

Critical as b-jet ubiquitous in Higgs final states.

b-jet Displaced - b-lifetimes ~pico-seconds Tracks - Typical speed (time dilation) ⇒ travel O(mm) Secondary Vertex ~mm Jet Lxy ~10 µm

d0 InteractionPrimary Drives specs. on detector resolution Vertex Point (Must know detector positions to ~µm)

Jet Detectors size apartment buildings, measure to accuracy of something barely visible to human eye. Major cost driver 55

1 Triggering

- LHC provides orders of magnitude more collisions than can save to disk - Can only keep 1 out of 40,000 events / Discarded data lost forever - Interesting physics is incredibly rare. ~1 Higgs per billion events

56 Triggering

57 Triggering

Triggering: Process of selecting which collisions to save for further analysis.

58 Triggering

Triggering: Process of selecting which collisions to save for further analysis.

Triggering in ATLAS: - Custom Electronics + Commodity CPU - Fast processing of images (micro-seconds / seconds) - Events rate from 40 MHz → 1kHz. - Data rate from 80 TBs (!) → 2 GB/s

59 Triggering

Triggering: Process of selecting which collisions to save for further analysis.

Triggering in ATLAS: - Custom Electronics + Commodity CPU - Fast processing of images (micro-seconds / seconds) - Events rate from 40 MHz → 1kHz. - Data rate from 80 TBs (!) → 2 GB/s Another major cost driver

60 The Cannon

Most of the time protons miss one another Cant aim with enough precision to ensure a direct hit each time Need to collide bunches of tightly packed protons to ensure hit LHC: 10^11 protons per bunch

61 The Cannon

Most of the time protons miss one another Cant aim with enough precision to ensure a direct hit each time Need to collide bunches of tightly packed protons to ensure hit LHC: 10^11 protons per bunch

proton proton

62 The Cannon

Most of the time protons miss one another Cant aim with enough precision to ensure a direct hit each time Need to collide bunches of tightly packed protons to ensure hit LHC: 10^11 protons per bunch

proton proton

21 63 The Cannon

Most of the time protons miss one another Cant aim with enough precision to ensure a direct hit each time Need to collide bunches of tightly packed protons to ensure hit LHC: 10^11 protons per bunch

proton proton

21 64 The Cannon

Most of the time protons miss one another Cant aim with enough precision to ensure a direct hit each time Need to collide bunches of tightly packed protons to ensure hit LHC: 10^11 protons per bunch

proton proton

Can in principle be calculated by the theory In practice, calculations extremely hard (αS so big) So extract from measurements in data 21 65 What We Measure Probability for process to happen given in terms of an area: Cross-section

66 What We Measure Probability for process to happen given in terms of an area: Cross-section Event Rate = Cross-Section × Particle Flux

Rate certain pictures (Directly measured)

67 What We Measure Probability for process to happen given in terms of an area: Cross-section Event Rate = Cross-Section × Particle Flux

Rate certain pictures Known input from LHC (Directly measured) Protons /area / time

68 What We Measure Probability for process to happen given in terms of an area: Cross-section Event Rate = Cross-Section × Particle Flux