LHC: unbelievable pursuit for the unimaginablemazumdar/talks/IITM.pdf · • Ancient civilizations...

LHC: the unbelievable pursuit for the unimaginable

Kajari Mazumdar

Department of High Energy Physics

Tata Institute of Fundamental Research

Mumbai

http://www.tifr.res.in/~mazumdar

[email protected]

Colloquium, IIT, Madras. 14 January, 2015

http://www.tifr.res.in/~mazumdar

• Ancient civilizations constituents of the universe:

Earth, Air, Fire, Water

• By 1900, nearly 100 elements!

• 1936 three basic particles: proton, neutron, electron

The eternal question of mankind

• Which principles govern energy, matter, space and time at the most elementary level?

• What is the world made up of? • How does it work? High Energy Physics tries to answer these.

Today

• Are quarks, electron, elementary particle?

• What lies within …? 14 January, 2015 2

Atom: 10-10 m Nucleus: 10-14 m Nucleon: 10-15 m

K. Mazumdar

Essential tool: Microscope

The probe wavelength should be smaller than the distance scale to be probed.

xE

41 mm 10 eV21 nm 10 eV

20 1310 m 10 eV

10 TeV

(1 eV = 1.6 * 10 -19 Joule)

Typical energy scales: • Motion of air atom, room temp: 0.04 eV • Chemical reactions/atom, visible photons of light: 1 to a few eV • Nuclear reactions, per atom: 1 MeV • Rest energy mc2 of proton: 1 GeV • Each proton in each LHC beam:

4 TeV (4*1012 eV) during 2010-2012, 6.5 TeV from 2015!

• We have already probed matter up to a distance scale of ~ 10-18 m with probes of energy ~ 100 GeV.

• LHC probes length scales ~ 10-19 to 10-20 m.

14 January, 2015 3 K. Mazumdar

10 thousand km

Connection with our Universe

4 14 January, 2015 K. Mazumdar

We belong to Milkyway galaxy

Our beautiful blue planet

• A typical galaxy: 100 million larger than the earth! Contains ~ 1012 stars!

• Our universe contains hundred thousand million galaxies

10 23 stars:

all made up of same elements of matter created 14 billion yrs ago!

tera

sc

ale

Superstrings ?

Unified

Forces

Inflationary

Expansion

Separation

of Forces Nucleon

Formation Formation

of Atoms Formation

of Stars

Today

Big Bang

Time 10-43 s 10-35 s 10-10 s 10-5 s 300 000 years 109 years 14∙109 years

Energy 1017 TeV 1013 TeV 1 TeV 150 MeV 1 eV 4 meV 0.7 meV

Travelling back in time

30 K


Energy =kT,

Length scale = hc/E

1027 K 1032 K 1015 K

Atom Proton

Big Bang

Radius of Earth

Radius of Galaxies

Earth to Sun

Universe

Study physics laws of first moments after

Big Bang increasing symbiosis between

Particle Physics, Astrophysics and Cosmology.

LHC

Hubble ALMA

VLT AMS

Dimensions in Physics

14 January, 2015 6

Technological advancements crucial

K. Mazumdar

the Super-Microscope

LHC

Present Wisdom

7

• All behaviour of the matter particles (fermions) can be explained in terms of few forces carried by the exchange / carrier particles (bosons).

• All interactions behaved as a single one when the universe was much younger and hotter idea of unification!

Connects the largest with the smallest entities in the universe.

14 January, 2015 K. Mazumdar

Knowing the mass, electric charge, spin etc. , theory can predict the results of experiments.

20

Institute of Physics Peter Kalmus Particles and the Universe

Forces

Gravity

falling

objects

planet

orbits

stars

galaxies

inverse

square law

graviton

inverse

square law

photon

short

range

W±, Z0

Electro-

magnetic

atoms

molecules

optics

electronics

telecom.

Weak

beta

decay

solar

fusion

Strong

nuclei

particles

short

range

gluon

BUT MATTER IN THE UNIVERSE IS NEUTRAL, because positive and negative charges cancel each other precisely. Gravitation is the dominant force in the Universe

Relative strength of gravitation, weak, electromagnetic, strong interactions ~10-40 : 10-5 : 10-2 : 1

Fundamental Forces


14 January, 2015 9

• Cathode Ray Tube: electron (1897) • Compton scattering expt. : Photon (1905, 1923) • Cosmic Rays: Positron (1932), Muon (1936) • Beta decay (nuclear reactors): electron neutrino (1956) Using accelerators: • rest of the particles • Higgs boson (LHC 2012)

K. Mazumdar

Non-accelerator methods

1) g for electromagnetic interaction 2) W ±, Z for weak .. 3) 8 gluons for strong ..

Matter particles

constituents

of everyday

matter How did we achieve this picture?

The messengers of the forces:

Particles and their discoveries

Five fold symmetry Radial symmetry Reflection/Bilateral symmetry

Dogma of Symmetry

Symmetry for practical applications eg., position of eyes, weighing balance.


Symmetry considerations play crucial role in modern physics.

Highlights of 20th century physics

• Special relativity

• General Relativity

• Quantum Mechanics

• Quantum Field Theory

• Standard Model of elementary

particles and their interactions

First example of embedded symmetry in physical law: Newton’s law:

Covariant under rotations F, a changes same way under rotation. Invariant under Galilean transformations F, a does not change in a boosted reference frame.

F = m a

Mathematics Physics • Calculus • Complex numbers/functions • Differential geometry • Group theory • Hermitian operators, Hilbert space •….

Symmetry of a physical system is a physical or mathematical feature of the system (observed or intrinsic) that is "preserved" under some change.


• The temperature of a room translational symmetry.

• Symmetry of a mathematical function: a2c + 3ab + b2c

Manifestation of symmetry

Electromagnetism: Maxwell’s equations • First attempt to combine electricity & magnetism. • Invariant under Lorentz transformation. • Also invariant under gauge transformation.

• Define scalar (f) and vector (A) potentials related to electric & magnetic fields: E = −∇f − ∂A/∂t, and B = ∇ × A • E and B remains unchanged even if we change the potentials as: f′ = f − ∂L/∂t and A′ = A + ∇L, where L is a function of (x, t).

Gauge transformation


Quantum theory is invariant under constant phase transformations of wave function This symmetry leads to charge conservation. If the phase is a function of space-time, the phase invariance is lost. Gauge symmetry demands quantum theory of elementary particle, say electron, should be invariant under space-time dependent phase transformations. • To ensure the invariance, one has to introduce a vector field into theory. • This vector field corresponds to the photon (g), carrier of EM interaction. The role of photon as carrier particle logically defined.

Gauge Symmetry

Gauge Invariance, proposed by Hermann Weyl, is

the cornerstone of modern day particle physics.


Electromagnetic and weak interactions are similar in nature.

Electroweak symmetry : basic idea

14

Enrico Fermi was the first to write down a theory of beta decay (1934), with the name neutrino coined by Pauli.

Improved theory (1956): Intermediate Vector Bosons: proposed by Sudarshan and Marshak, and, independently, by Feynman and Gell-Mann.

Neutrino

electromagnetic weak

n p e- n

d -1/3 u +2/3 W-1 ( e-1 n) d

u

W

Weak Interaction; • Responsible for some kinds of radioactivity (b decay) • Only force neutrinos (n) can feel, makes sun burn. • Typically very slow process: C14 decay takes 6,000 years! • Carried by weak bosons : charged ( W±) or neutral (Z0)


15

The recognized giants of the standard model

• 1967: Steven Weinberg and Abdus Salam used their ideas to build a model of electron mass and weak boson mass.

• Also earlier ideas by Sheldon Glashow.

Nobel prize in 1979

Nobel prize in 1999

• Not much attention paid to 1967 work until 1972 paper by Gerard ’t Hooft and Martinus Veltman,

which relied even more explicitly on Higgs’ idea.

It was indeed time for experimental confirmation of the Higgs sector!

14 January, 2015

• Results of all the past experiments matched well to the theoretical prediction of Standard Model corresponding theoretical description is correct.

K. Mazumdar

• Gauge symmetry is required to correctly describe the interaction of matter. • Quantum electrodynamics is the most complete and successful theory. • The theoretical predictions match very well with experimental results. Eg. , value of fine structure constant matches upto 9 digits after decimal!

• Carrier of EM interaction, Photon, is massless. • Charged carriers of weak interaction, W+, W- , should couple to photon couplings are universal unification of two forces Electroweak theory 4 carriers particles, spin-1 boson,: g, W+, W- , Z0 .

• Carriers of weak interaction needed to be massless to respect symmetry with electromagnetic interaction infinite range expected like in EM. • Experimentally observed: weak interaction has short range the carriers must be massive!

Unification of two forces?

However there is a big problem

Several scientists, in independent groups, worked the way out for the mass generation of carrier particles of weak interaction during early 1960s.


Nambu, in 1960, proposed how it is possible to have our cake and eat it. • The equations describing the system are invariant under some symmetry. • The ground state of a system breaks the symmetry in the dynamics. phase transition

Spontaneous Symmetry Breaking

In nature, spontaneous symmetry breaking is not very uncommon. eg., a ferromagnet below and above Curie temperature

Symmetry disappears at low energy, reappears at high energy.

Electromagnetic and weak interactions are combined together in a single Electroweak theory where symmetry is spontaneously broken at lower energy

between EM mediator g and mediators of weak interaction W+, W-, Z0 .

Nobel prize in 2008


Nambu’s idea was taken up in earnest in 1964 by three groups to propose theoretical argument for mass generation in weak interaction:

1. Francois Englert and Robert Brout at Brussels

2. Peter Higgs in Edinburgh

3. Gerald Guralnik, Carl Hagen and Tom Kibble at London

The spontaneous symmetry breaking leads to the existence of an additional, spin-0, elementary particle called the Higgs boson.

Electroweak symmetry breaking and its consequences

Symmetric position is not the ground state!

• At high energy W boson appears massless, ie., at short distance scale of less than ~1 fermi (10-13 cm). • Close to the ground state, at low excitation energy,

symmetry disappears and, the effect corresponds to massive W, Z bosons.

Experimental verification of this hypothesis was essential. 14 January, 2015 18 K. Mazumdar

The drag in movement

• Simply put, there is an all pervading Higgs field.

• All particles necessarily interact with this field and thereby acquire mass.

• Coupling of a particle with Higgs boson depends on its mass.

• The Higgs field also interacts with itself as well resulting in its own mass!


Mass spectrum of elementary particles

The missing piece till now

Mass of the Higgs boson could have been anything up to ~ 1 TeV equivalent energy density is needed for Higgs boson to be created in the laboratory.

• LHC has been built to discover the Higgs particle and study EWSB

• LHC experiments discovered the Higgs

boson in 2012, hypothesized ~ 50 years back! Great triumph of human intellect • Hunt for the particle started seriously

during 1980s. LHC project: largest human endevour ever taken up.


21

Why was the Higgs discovery so important

• Success of standard model crucially depended on the experimental confirmation of the “Higgs mechanism” the existence of the Higgs boson. • We have now all the essential members of the particle zoo in SM.

Must appreciate the elegance of the idea of unification and other hall

marks achieved in the field during the last century.

Gigantic efforts in many fronts led to the success at the LHC, in first phase of its operation (2010-13). -- 2012: “a Higgs like new particle” -- 2013: “a Higgs boson” Physics Nobel prize to P. Higgs and F. Englert

After the discovery: Is it the Higgs boson of standard model ? • Is there any other Higgs particle? • Is the resonance a window to new physics? • Future of LHC is very bright in resolving these questions.


• LHC is the world’s most powerful microscope doing nanonano physics. • When protons collide sufficient energy accumulates occasionally in short-distance

reactions so that heavy particles could be produced in the lab, singly or as pairs E = mc2 • The larger the energy the greater the variety of particles produced

Perfect role of Large Hadron Collider

Accelerates charged particles (protons or lead ions) using electric field and bending them in circular arc using magnetic field, repeatedly.

LHC: the giant marvel of technology

• 100-150 m under the surface

• 27 km at 1.9 K (superfluid He)

• Vacuum ~ 10-13 Atmosphere

• Super-Conducting coils: 12000 tonnes

• Temperature generated at LHC due to proton-proton collision ~1016 0c, compare with sun: 5506 0c, a matchstick: 250 0c

• LHC machine maintained at -271 0c vs. home freezer is at -8 0c Boomerang nebula: -272 0c, antarctica: -89.2 0c,

• One of the fastest race tracks: protons zipping past with 99.999999% of velocity of light around 27 km of LHC ring 11000 times/sec.


• 2 major, multipurpose experiments which discovered the Higgs boson: ATLAS and CMS • Other big experiments: LHCb, ALICE

14 January, 2015 K. Mazumdar 24

Components of accelerators • electric field produced by radio-frequency (RF) resonant cavities particle acceleration • magnetic field produced by electromagnets • guides and focuses the beam in circular path

Superconductivity gives access to stronger fields and reduces the energy loss in RF cavities and magnets

compact accelerators (smaller bending radius) higher quadrupole gradient higher focusing/luminosity higher electric fields (DC) Special requirements for accelerator magnets advances in SC technology Type-2 SCs (best alloy NbTi) retain superconductivity till high enough B-field flux gradient created via imperfections to carry high current density bonding SC with copper provides path to high current in case of instability SC wires into fine filaments (10- 50 mm) to stablize movement of mag. flux within SC when magnetic fields are applied. Twisted composite wires (dia. 0.3 – 1 mm) to decouple filaments magnetically.

Superconductivity and particle accelerators


• 5000 SC LHC magnets @1.9 K (superfluid He) + Liq. He in heat exchanger tubes along the magnets. • 4* field produced by classical electromagnets, • Power consumption: 10 *cheaper • ~1300 dipole superconducting magnets, 15 m long • 8.4 Tesla, current 11,700 A for Ebeam = 7 TeV

Magnet quench can still happen due to mechanical effects The field due to high current moves the magnet Epoxy raisin contracts more than SC wire! Friction causes rise in temperature use steel collars to contain magnetic force

I

LHC magnets

• different field shapes need different windings - simplest is the solenoid,

- transverse field for accelerators

• End turns to be shaped


Accelerating the protons in LHC

4.5 hrs. to fill each LHC ring 20 mins. to accelerate to nominal energy Collisions for ~ 20 hrs. Front-end electronics ready every 25 ns

What happens in LHC experiment

Proton-Proton 1380 bunch/beam Protons/bunch 2. 1011

Beam energy 4 TeV Luminosity 7.5*1033 /cm 2/s Total event rate 5.4*108 Hz Higgs production <1 Hz

Summer, 2012

20 years to build, > 20 years to operate Great opportunity for students of several generations!

s27 14 January, 2015 K. Mazumdar

Mandate: 1. Discover Higgs particle or rule out its existence. 2. Elucidate on physics at the new energy range of TeV 3. Search for the candidate of the dark matter in the universe. …….

Cartoon of ATLAS detector


Policy of the experiments: • Measure the position and momentum of photons and leptons (electron, muon,

tau) with high accuracy and reliability. • Measure hadronic shower (jets of particles, like pion etc.) and missing energy.


~66 Million silicon pixel channels ~10 Million Silicon microstrip channels ~75000 PbWO 4 crystals, 137000 Silicon preshower ~15k Hadron Calorimeter channels 250 Drift Chamber (170k wires), 450 Cathode Strip Chamber (~200k wires) , ~ 500 Barrel Resistive Plate Chambers and ~ 400 endcap Resistive Plate Chambers Muon and calorimeter trigger system 40000 Hz Data Aquisition system(~ 10000 CPU cores) Grid Computing (~ 50 000 cores), offline (> 2 Million lines of source code).

Essentials of CMS detector

Representation of final stage outcome

Any event 109/s Higgs event: 0.2 /s

Data rates

Data archiving rate ~ few hundred Hz


LHC collides 6-8 hundred million proton on-proton /second for several years.

Only 1 in 20 thousand collisions has an

important tale to tell, but we do not know which one! need to search through ALL of them! 15 PBytes (1015 bytes) of data/year Analysis requires ~100,000 computers to get results in reasonable time.

Distributed computing is essential

Science without borders

LHC computing in hard numbers

World wide LHC computing GRID was the

natural evolution of internet technology.


1. Share more than information Data, computing power, applications in dynamic, multi-institutional, virtual

organizations. 2. Efficient use of resources at many institutes.

People from many institutions working to solve a common problem.

3. Join local communities. Need comparatively large hardware resources with high

speed connectivity

4. Interactions with the underneath layers transparent & seamless to the user.

From Web to Grid Computing

CMS and ALICE Tier2 GRID computing

centers in TIFR (Mumbai) and VECC (Kolkata).

• Today ~ 200 sites

• ~40k CPU cores

• ~100 PB disk

WWW was born in early 1990s to satisfy the needs of previous generation HEP experiments.


CMS Collaboration: 1800 Ph.D.s + 1600 students + 800 engineers from 200 institutes around the worlld

Only a small fraction of ~4500 people who made CMS possible

~ 120 Indians

14 January, 2015 33

C CMS experiment

K. Mazumdar


Indian contributions in LHC:

• Main accelerator magnet components

• CMS and ALICE experiments

• Grid computing

presently 13 Indian groups of varying strengths. • BARC • Delhi U. • IIT, Bhubaneswar • IIT, Madras (most recent)

• IIT, Mumbai • NISER • Panjab U. • Shoolini U. • SINP • TIFR • Visva-Bharati U • Currently about 40 physicists, 15 engineers + other technical staff, • 40 Ph.D. students (+15 students who have finished Ph.D. already)

India-CMS collaboration

Significant contribution from India in various fronts of CMS experiment, in spite of ‘distance’ and ‘time-zone’ factors.

Cartoon of current CMS detector

HO TIFR, U.Panjab

Silicon preshower BARC, U.Delhi

RPC detector BARC, U.Panjab 14 January, 2015 35 K. Mazumdar

Event rate of a physical process: R = s L = cross section*instantaneous luminosity

0.5 Million Higgs particles produced till now in each interaction point

Each constituent of proton (quark/gluon) carries only a fraction of the parent energy.

LHC motivations: explore, search, measure

Background rate ~1012 times higher efficient and diligent strategy developed over years.


simulation

• Higgs boson decays within ~ 10 -24 s. Not all decay channels are experimentally suitable. Discovery mode H gg , Branching ratio= 0.23% • Experimental signature final state with 2 photons. Search for resonance structure in diphoton mass distribution

Crucial for mass resolution: • individual energy measurement for each photon • angle between 2 photons huge investments in every sense paid very well.

m2γγ= 2 E1 E2 (1-cosα)

Higgs decaying to a pair of photons


Golden decay channel H ZZ* 4 leptons

Signal: 4 energetic, isolated leptons ( combination of pairs of electron or muon) Use kinematic properties of final state leptons to discriminate signal vs. background on event-by-event basis. Best channel for discovery & determination of properties mass, width, spin, parity, couplings. Z 4l

H 4l

4l continuum Backgrounds:

Interference of diagrams for off-shell resonance and continuum background must be taken into account.

14 January, 2015 38

Lot of experimental investments in measuring decay leptons accurately

K. Mazumdar

Signal

Work of a detective

• Measurement of mass Fundamental property, not predicted by theory Once measured, SM predictions are completely determined Use resonance structure in high resolution channels H gg, H 4leptons

CMS : 125.03 ± 0.26 (stat.) ± 0.14 (syst.) GeV ATLAS: 125.36 ± 0.37 (stat.) ± 0.18 (syst.) GeV

GH < 22 MeV ~ 5GH SM

Compatible within errors

• Total width of Higgs boson • Spin-Parity JP = 0+ • There is no other particle of different spin or similar mass • Couplings of Higgs to various particles are similar to as in standard model


mu = 0.003 mt = 184 mb = 5.0 me = 0.0005446 mm = 0.1126

Eg., it does not explain this bizarre set of numbers for mass (in GeV)

Is our job over?

By no chance! Higgs boson fixes a crucial problem, and accounts for the origin of mass, but it leaves a lot unexplained

• A Higgs of mass 125 GeV indicates existence of “new physics” .

• However, our score card = 0 till now

• There are many reasons to believe that there is a lot of unknown,

new physics at higher energy.

Future operations of LHC will guide us. • 2015 – 2030: LHC operates with intermittent stops for ~2 -3 years centre of mass energy 13 TeV, but gradually increasing luminosity • allows to explore physics beyond standard model upto energy scale ~ few TeV Supersymmetry Other possibilities for beyond standard model physics



Negative searches so far: Supersymmetry

Similar for ATLAS


Hunting for the exotica

Similar for ATLAS

43

Scattering of longitudinal vector bosons

Each diagram ~ s2

s(ppWW) > s(pp anything)!

Unitarity restored by scalar Higgs Cancellation also requires Higgs < 800 GeV

• Taming the rate could be managed by alternative EWSB mechanism Search for possible resonances in future operations of LHC

LSB > 1TeV

SB sector

strongly coupled d

s/d

M(V

V)

LSB < 1TeV

SB sector

weakly coupled

14 January, 2015

Study WW Scattering spectrum, σ(WWWW) vs M WW

Fundamental probe to test the nature of Higgs boson and its role in EWSB

Energy K. Mazumdar

Seeing the dark!

Passage of 2 galaxies 100 M years back

Rotation curve of a galaxy

• With increasing distance the gravitational pull between 2 bodies should decrease.

• Observations suggested gravitational pull

from additional heavy objects which are not yet detected (through EM interaction).

• Identification of the dark matter is one of the

most intriguing problem at present.

LHC can shed light on the nature of the dark matter

Constituents of the universe



LHC Run2 Road-map

• Energy 13 TeV

• More intense beams

• Detectors need important upgrades for good performance India expects to play bigger role.

• LHC experiments have discovered Higgs particle of mass 125 GeV.

• No exotic discovery as yet

• Established : Origin of mass (scalar field BEH mechanism) of particles in a

quantum field theory with local (point-like) gauge interaction.

• Starting from a reductionism strategy: question of structure of matter

evolved into the question of origin of interactions (local gauge symmetries)

and matter (interaction with Higgs field)

• The rise in centre of mass energy at LHC in next run, gives access to new

territory for the searching the unknown.

• Great opportunity for students!

• However , we shall always manage to know only a drop of the ocean!

Summing it up

46 Stay tuned! 14 January, 2015 K. Mazumdar

backup


1. At the core is a device called the inner tracker detects and analyzes the momentum of particles passing through the detector.

2. Surrounding the inner tracker is a calorimeter measure the energy of particles by absorbing them. 3. The outermost subdetector is muon spectrometer measures muon position and momentum. Scientists look at the path the particles took and extrapolate information about them. Reconstruct 20K charged tracks in a single event (lead-lead collisions at LHC)

Essential components of a detector

Data collected by an experiment in a year ~ Peta Byte how to handle? 14 January, 2015 48 K. Mazumdar

• Background distribution mostly Gaussian

stability of result expressed in terms of width s of the Gaussian.

• Characterization of excess using test statistic

Significance where

• Greater the significance (s) minor the p-value lower is the chance

that the observed excess is due to background fluctuation.

Statistical analysis

Signal strength for H gg



Superconductors and magnets

Critical current density at liq. He temp. (4.2 Kelvin) is a function of magnetic field

At 6T, current density in NbTi is 2000 A-mm -2

Conventional magnet with Cu winding 2 T

For long magnets, current degrades with increasing size. winding crucial to achieve cryostatic stabilization.

Cri

tica

l cu

rren

t d

ensi

ty A

.mm

-2

10

102

103

104

Magnetic field (Tesla)

Nb3Sn

NbTi

Conventional

iron yoke

Niobium titanium NbTi is the standard ‘work horse’ of the superconducting magnet business:

it is a ductile alloy, NbSn not.

critical surface: the boundary between superconductivity and normal resistivity in 3 dimensional space.

• superconductivity prevails everywhere below the surface

Curr

ent

den

sity

(kA

.mm

-2)

Jc

c

Bc2

14 January, 2015

51

Synchrotron light source producing high energy X-rays Probe superconducting materials Materials research Beams of photons, neutrons and muons: study materials at the atomic level. Protein modeling Synchrotron light to solve the 3D structure of proteins. Controlling power plant gas emission electron beams control emission of sulphur , nitrogen oxides. Super conducting accelerators in hospitals short-life radio-nuclides for diagnosis Hadron therapy Proton and ion beams for the treatment of deep seated tumours. Positron Emission Tomography (PET) Radioisotopes used in PET-CT scanning Ion implantation for electronics Build fast transistors and chips for digital electronics Hardening materials Replacing steel with X-ray cured carbon composites energy consumption halved! Cultural heritage Particle beams for non-destructive analysis of works of art, ancient relics. K. Mazumdar

Accelerators and the society


Measure the position and momentum of photons and leptons (electron, muon, tau) with high accuracy and reliability. Measure hadronic shower (jets of particles, like pion, kaon etc.) and missing energy.

Slice of CMS detector

Individual analyses

Significance of observation of 125 GeV Higgs boson: CMS summary

sobs /sSM = m

measure of signal strength compared to SM expectation for Higgs mass at the fitted value.

Illustration

14 January, 2015 53 CMS: m = 1.0 ± 0.09(stat. )+.08-.07 (theo.)± 0.07(syst) compatible with SM K. Mazumdar

LHC: unbelievable pursuit for the unimaginablemazumdar/talks/IITM.pdf · • Ancient civilizations...

Documents

Transcript of LHC: unbelievable pursuit for the unimaginablemazumdar/talks/IITM.pdf · • Ancient civilizations...