MEET THE TIME MAGAZINE PARTICLE OF THE YEAR: THE !

Saptaparna Bhattacharya July 11th - 22nd, 2016 Lets start at the beginning!

http://poy.time.com/2012/12/19/the-higgs-boson-particle-of-the-year/ Introduction

• I am Saptaparna Bhattacharya, a post-doctoral scholar in the department of Physics and Astronomy at Northwestern University in Chicago. • My research is based on the data from the at CERN. • I have worked on the first published result that uses the Higgs boson as a probe for New Physics. • My interest lies in various models of New Physics, ranging from to exploring the possibility of finding microscopic black holes. • I am also interested in exploring interesting techniques for data analysis. But, enough about me, where are you guys from? Current Enrollment

We are a class of 17 students! Let me quickly check to see if you are all here! What we did last summer!

Di-photon invariant mass h_InvariantMass_PhPh Higgs to ZZ invariant mass h_InvariantMass_HZZ Entries 85893 Entries 13235 30000 Mean 125.9 Mean 124.2 RMS 2.636 RMS 3.147

5000 25000 Events/2.0 GeV Events/2.0 GeV 20000 4000 Higgs boson mass distribution Higgs boson mass distribution 15000 3000

10000 2000

5000 1000

0 0 100 105 110 115 120 125 130 135 140 145 150 100 105 110 115 120 125 130 135 140 145 150 m [GeV] m [GeV] γγ µ µ µ µ

Di-muon invariant mass h_InvariantMass_MuMu Tranverse Mass with Muons Entries 37122 h_TransverseMass_Mu Mean 90.66 Entries 37791 RMS 4.506 5000 4000 Mean 65.9 RMS 15.36 3500 4000 Events/GeV Events/1.0 GeV 3000 Z boson mass distribution 3000 2500 W boson transverse 2000 mass distribution 2000 1500

1000 1000 500

0 0 70 75 80 85 90 95 100 105 110 0 50 100 150 200 250 300 m [GeV] mµµ [GeV] T Outline

• The course is roughly structured into two parts: • Laying down the fundamentals. • Making plots and interpreting them. • What are the fundamentals: • We have learned Newtonian mechanics in school. • We can use Newton’s laws to solve for complex problems like planetary motion, explain macroscopic phenomena around us. • But what happens when particles around us become very energetic. • Or we start looking at objects the size of the atom. Outline • What governs the dynamics of particles beyond what we see around us? • In other words, do Newton’s laws always hold? • What is Experimental ? • What are the experiments out there? • What does a detector look like? • How was the Higgs discovered? • Make plots for ourselves next week to understand the process of the Higgs discovery. Course Syllabus Do you have access to the course syllabus? Here’s what it looks like: How do we communicate?

Did you guys get the email I sent yesterday? This was the email address I sent it to: [email protected]

Hi All,

Just a quick request: have any of you seen the movie "Particle Fever"? If you have, then that's great! If you haven't you might consider watching it during our 2 week long course. I know it is available on netflix (instant streaming).

This is not an official assignment though. Just a suggestion! :)

See you soon, Sapta Quiz 1

Please respond to this survey : https://www.surveymonkey.com/r/M6ZFYXN

Please respond to all but the last two the questions. The last two questions are based on some of the things we will discuss in class. This survey is for my learning and I will not be grading anyone based on its results! So, no pressure! Predictive power of Newtonian Mechanics

• All planets move in elliptical orbits with the sun at the focus of the ellipse. • A line that connects a planet to the sun sweeps out equal areas in equal intervals of time. • The square of the period of any planet is proportional to the cube of the semi-major axis of its orbit. Kepler’s laws Kepler’s laws Kepler’s laws Kepler’s laws Kepler’s laws Kepler’s laws Kepler’s laws

Feel free to checkout: https://twiki.cern.ch/twiki/bin/view/CMSPublic/KeplersLaws Sense of scale

From the microscopic to the large scale structures. Units in physics

http://home.web.cern.ch/topics/large-hadron-collider Units in physics Our unit of choice in this course will be the electron- volt: eV In more familiar units: 1 electron volt = 1.60217657×10-19 joules It is the amount of energy gained (or lost) by an electron moving across an electric potential difference of one volt.

We will use natural units in this course, which means, speed of light, c=1. Therefore, mass and energy units will be the same. So, don't be alarmed when I say that the mass of the proton is ~1 GeV. Constituents of Matter: What is an atom?

The Hydrogen Atom: simplest possible atom. Remember this as we will later connect it to the Large Hadron Collider. Constituents of Matter Turns out that the previous slide only tells you half of the truth. Protons and neutrons are not fundamental and are composed of quarks. Look at the mass hierarchy! Why the masses are exactly what we observe is an interesting question… Cosmic Muons

http://www.nevis.columbia.edu/~kmisquitta13/muon.html The Cosmic Ray Story Origin of cosmic rays.

This proton travels through interstellar space and reaches the earth. It then interacts with air molecules. Cosmic ray interactions with the atmosphere. A slew of particles are created. One of the stable particles are muons which can be detected in a cloud chamber. The pion decays to a neutrino and a muon. The muon is a stable particle that can be detected using a cloud chamber.

Notice that the muon and the neutrino are of the same kind. This is a muon neutrino. There are electron and tau neutrinos that are produced when electrons and taus decay. These decay chains involve interactions different from the one shown here. The cloud chamber has air and alcohol vapor. The dry ice keeps the lower layer very cold. So, while the top layer has alcohol at a higher temperature, the bottom layer is much colder. When a muon passes through the chamber it ionizes the alcohol which then causes alcohol droplets to condense around the path of the muon. A muon traveling through the cloud chamber. A magnetic field can be applied to see charged particle tracks curve under its influence. The muon decay problem

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html The muon decay problem: the need for relativistic calculations

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html The muon decay problem: the need for relativistic calculations

Non relativistic:

Relativistic:

Υ= 1/sqrt(1 - (v/c)^2)

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html http://www.phys.vt.edu/ ~takeuchi/relativity/notes/

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html Quiz 2

Each of you has a copy of this book. Can you browse through it and list the fundamental particles along with some basic properties like the charge and mass of each particle? Fundamental particles and forces

If you look around, you will see particles, objects, collections of particles moving around due to the application of various kinds of forces on them.

How are forces described in the context of fundamental particles? Fundamental particles and forces

• The strong interaction is very strong, but very short- ranged. It acts only over ranges of order 10-13 centimeters and is responsible for holding the nuclei of atoms together. It is basically attractive, but can be effectively repulsive in some circumstances. • The electromagnetic force causes electric and magnetic effects such as the repulsion between like electrical charges or the interaction of bar magnets. It is long-ranged, but much weaker than the strong force. It can be attractive or repulsive, and acts only between pieces of matter carrying electrical charge. • The weak force is responsible for radioactive decay and neutrino interactions. It has a very short range and, as its name indicates, it is very weak. • The gravitational force is weak, but very long ranged. Furthermore, it is always attractive, and acts between any two pieces of matter in the Universe since mass is its source. Fundamental particles and forces

We have already been introduced to some of these particles. The W, Z, photons are gluons are mediators. They are the carriers of the weak, electromagnetic and strong forces.

What’s missing? Fundamental particles and forces

Let’s go back to this picture: Electromagnetic force: Electromagnetic force: Gravitational: forms a category by itself. missing from the Standard Model! Interesting! The Large Hadron Collider The Large Hadron Collider

• The Large Hadron Collider (LHC) is the world’s largest and most powerful particle accelerator. It first started up on 10 September 2008, and remains the latest addition to CERN’s accelerator complex. The LHC consists of a 27-kilometre ring of superconducting magnets with a number of accelerating structures to boost the energy of the particles along the way.

• Inside the accelerator, two high-energy particle beams travel at close to the speed of light before they are made to collide. The beams travel in opposite directions in separate beam pipes – two tubes kept at ultrahigh vacuum. They are guided around the accelerator ring by a strong magnetic field maintained by superconducting electromagnets. The electromagnets are built from coils of special electric cable that operates in a superconducting state, efficiently conducting electricity without resistance or loss of energy. This requires chilling the magnets to -271.3°C – a

temperature colder than outer space.

• For this reason, much of the accelerator is connected to a distribution system of liquid helium, which cools the magnets, as well as to other supply services.

Tex t f r o m : http://home.web.cern.ch/topics/large-hadron-collider The Large Hadron Collider: Accelerator complex The Large Hadron Collider

• Thousands of magnets of different varieties and sizes are used to direct the beams around the accelerator. • These include 1232 dipole magnets 15 metres in length which bend the beams, and 392 quadrupole magnets, each 5–7 metres long, which focus the beams. • Just prior to collision, another type of magnet is used to "squeeze" the particles closer together to increase the chances of collisions. • The particles are so tiny that the task of making them collide is akin to firing two needles 10 kilometres apart with such precision that they meet halfway! The Large Hadron Collider

Video http://home.web.cern.ch/about/accelerators The Large Hadron Collider

The tevatron at Fermilab operated at 1.96 TeV

Center of mass energy: The Large Hadron Collider: Facts Panoramic view of the LHC.

http://home.web.cern.ch/about/updates/2013/09/explore-cern-google-street-view The CMS Detector The trajectory of particles Origin of Mass: Higgs Boson Higgs Production Higgs Decay Higgs Events

Candidate Higgs decay to four electrons recorded by ATLAS in 2012. Higgs Events

Candidate Higgs Decay to four muons recorded by ATLAS in 2012. Discovery Plots

Mass distribution for the two-photon channel. The strongest evidence for this new particle comes from analysis of events containing two photons. The smooth dotted line traces the measured background from known processes. The solid line traces a statistical fit to the signal plus background. The new particle appears as the excess around 126.5 GeV. The full analysis concludes that the probability of such a peak is three chances in a million. Discovery Plots

Mass distribution for the four-lepton channel. The search with the purest expected signal is done by examining events with two Z bosons that have decayed to pairs of electrons or muons. In the region from 120 to 130 GeV, 13 events are seen where only 5.3 were expected. The complete analysis concludes that the probability of such an excess would be three times in ten thousand if there were no new particle. Discovery Plots

Experimental limits from ATLAS on Standard Model Higgs production in the mass range 110-600 GeV. The solid curve reflects the observed experimental limits for the production of a Higgs of each possible mass value (horizontal axis). The region for which the solid curve dips below the horizontal line at the value of 1 is excluded with a 95% confidence level (CL). The dashed curve shows the expected limit in the absence of the Higgs boson, based on simulations. The green and yellow bands correspond (respectively) to 68%, and 95% confidence level regions from the expected limits. Higgs masses in the narrow range 123-130 GeV are the only masses not excluded at 95% CL. Discovery Plots

The probability of background to produce a signal-like excess, for all the Higgs boson masses tested. At almost all masses, the probability (solid curve) is at least a few percent; however, at 126.5 GeV it dips to 3x10-7, or one chance in three million, the '5- sigma' gold-standard normally used for the discovery of a new particle. A Standard Model Higgs boson with that mass would produce a dip to 4.6 sigma. Beyond the Higgs! A new physics process

http://atlas.ch/blog/?paged=5 Quiz 3

Please respond to this survey : https://www.surveymonkey.com/r/M6ZFYXN

Please respond to the last 2 questions of the survey. The Large Hadron Collider Disclaimer

Materials used in these slides are borrowed from various sources. I have tried to cite most of my sources, but if I have failed to cite a particular source, it is only a mistake and will be fixed.