October 2011 David Toback, Texas A&M University Research Topics Seminar 1 David Toback Texas A&M University Mitchell Institute for Fundamental Physics and Astronomy Texas Tech Colloquium March 2015 Cosmology and Particle Physics

A Different Type of Talk This talk is given at a funny time in my career. I’m finishing a 20 year career in collider physics searching for new particles, and moving to direct dark matter detection searches In the middle I made the transition from doing pure searches for new particles, to cosmology inspired searches Think about the collider physics as reproducing the conditions of particle production in the early universe –Could potentially explain the dark matter that is still around today March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 2

Prologue Continued… Big picture of what I’ve learned and how I now think about things  use the interface of cosmology and particle physics to point to the next steps This talk isn’t really the state of the art (like a theorist would give), but rather the perspective of an experimentalist who is looking towards doing the experiments over the next couple of years which are complementary to the LHC March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 3

The Big Picture in 2015 There are many BIG questions in 2015: Why is the top mass so much bigger than all the others? –Why is the top coupling to the Higgs so large? What protects the Higgs mass in the Standard Model? Is Supersymmetry a correct description of nature? Are there extra dimensions of nature? What is the mechanism that gives neutrinos mass? What is the dark matter that fills the universe? What is the dark energy that is causing the universe to accelerate? Why so much matter in the universe and so little anti-matter? What bigger theory does the SM approximate so well? String Theory? March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 4

How might one get the answers? We live in a time of remarkable scientific understanding Scientists are arrogant/crazy enough to think that it may be possible to solve major problems in Astronomy, Cosmology and Particle Physics with a single discovery that ties all three together Idea: Dark Matter is a particle that was created right after the Big Bang and has had a major impact on the evolution of the Universe and the stuff in it March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 5

Notes… (Apologies for the simplistic definitions) Astronomy is the study of things we can see through telescopes… Stuff in Universe (space) Cosmology is about trying to understand the origin and evolution of the Universe Particle Physics is about trying to understand the smallest things that make up the stuff in the Universe March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 6

Some Steps Along the Way/Outline 1.Some overview of where we are in our understanding of particle physics, and some of the outstanding questions 2.Some of what we know about dark matter, and why we think it might be a particle 3.Some guidance from the role we expect that dark matter played in early universe and its evolution until today 4.How I think about the right way to make progress, and what scientists (including me) are doing today to discover dark matter 5.Final Thoughts March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 7

Particle Physics The standard model of particle physics has been enormously successful The recent discovery of the Higgs at the LHC is a crowning achievement of our understanding of the mechanism of electroweak symmetry breaking and about particle mass in general March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 8

Dark Matter The Astronomical and Cosmological Evidence for Dark Matter is Overwhelming Also clear that none of the known SM particles is a good dark matter candidate March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 9

Fun Evidence that Dark Matter is a particle from Colliding Clusters of Galaxies March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 10 Blue is the part from lensing only “Fast  Dark Matter” Red part from observing the light “Slow  Atoms” A collider physics dream ;-)

Supersymmetry to the Rescue? Supersymmetry is one of the most compelling theoretical ideas in the last 40 years Can provide a dark matter candidate However, the most complete models have 128 free parameters Much of the thinking in the theoretical community is about the methods for the unification of the forces or the mechanism of SUSY breaking For example, in gravity mediated SUSY we get a simplification of the unification of the scalar and gaugino masses at the GUT scale Could help “protect” the Higgs mass, could unify the force couplings at the GUT scale March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 11

Discovery of the Higgs also changes the emphasis in searches March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 12 The Standard Model Corrections to Higgs boson mass not only finite, but in fact divergent Supersymmetry Fermion and Boson contributions to the Higgs cancel nearly exactly in supersymmetry The one loop divergences will cancel, provided that the SUSY particles have masses that are small enough… Maybe only Stop contributions matter? Nothing to do with SUSY?

Relationship between String Theory and SUSY Modern versions of string theory actually require SUSY Not many games in town that have the possibility of unifying gravity with particle physics March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 13

Optimist and Pessimist This is an exciting set of possibilities SUSY could explain the Higgs problem, unify the couplings, and explain dark matter But: –No evidence for SUSY –No evidence for String theory or the extra dimensions it requires –Why are the SUSY masses different from the SM masses? Asked differently, Why is SUSY broken? –Do we really think we can solve ALL of these problems with a single solution? –Last time we went looking, we found Dark Energy and we didn’t know we were looking for it March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 14

March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 15

Cosmology and Particle Physics? In the last decades, Cosmology has entered a Precision Era In addition to be exciting in its own right, it has the opportunity to teach us about particle physics March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 16

What is the Big Bang Theory? Not that Big Bang theory March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 17

It all started with a Big Bang… Bang… Ok… Then what? How did we get from the bang to the Universe we have today? March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 18

A Brief History of Time March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 19 The Big Bang  produces lots of particles Quarks combine to form protons and neutrons Protons and Neutrons combine to form the nucleus of an atom Nuclei and electrons combine to form atoms Atoms combine to form Stars and Galaxies The Earth and our solar system forms You listen to me talk Zero One millionth of one second after the Bang A few minutes A few hundred thousand years 100 million to 1 billion years 9 billion years ~13.7 billion years What’s Missing? When did the Dark Matter Show up? Clearly has had a major impact on the formation of structure in the universe, as well as the assembly of galaxies

September 2014 David Toback, Arnowitt Fest 20 Astronomy, Cosmology and Particle Physics: The Dark Matter in the Universe is made up of LOTS of particles that we haven’t discovered yet! Got created in the Early Universe like everything else and is still here today! Many models, like Supersymmetry, allow us to go beyond simply providing a candidate, they allow for a full Dark Matter relic density prediction Cosmological Connections Allow for Predictions

Is the Evolution of the Universe really this simple? Do we really believe that we have 6 types of quarks, 6 types of leptons, 6 bosons (depending on if you consider the graviton), and that set of things makes up ~5% of the universe but the next ~25% is ONE-AND-ONLY-ONE PARTICLE? And it essentially stopped interacting (except gravitationally) a picosecond after the bang? No reason to think its wrong, but is it REALLY that simple? Do we really think that the simplest models of SUSY can protect the Higgs AND give Dark Matter? Too simple? March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 21

Why I like the way we are going now If even some part of the dark matter was created in the early universe, sometime after a picosecond, we should be able to create it at LHC. Since it shouldn’t interact with the SM material of the detector, generic Missing Energy signals are the way to go! LHC is doing an excellent job here If the dark matter DOES interact with SM material at all, then we should be building detectors to identify those interactions. –Doing that now with CDMS and LZ Not saying we shouldn’t pay attention to the limits, but they are based on models that may or may not stand the test of time. But they ARE excellent models that can guide the searches to be both broad and deep March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 22

How to pick a Research Topic Need three things: 1)Answer the “So What?” question 2)Need a competitive advantage 3)The first steps need to be obvious March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 23

Three ways to look for Dark Matter A helpful Feynman Diagram March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 24 X X q q annihilation / freeze out indirect detection combination collider production scattering direct detection

Can we Make and Discover Dark Matter? High energy collisions between particles in the Early Universe Recreate the conditions like they were RIGHT AFTER the Big Bang If we can produce Dark Matter in a collision then we can STUDY it March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 25

Expensive Dark Matter? High Energy Collisions  Dark Matter Particles LHC  ≈1 ps after the Big Bang March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 26 Dark Matter Particle Detector Proton Dark Matter Particle Ok… Its more complicated than this since Dark Matter Particles don’t easily interact with detectors… Nor do we usually produce them directly

Limits on SUSY from LHC CMS and ATLAS have huge number of peoples searching extensively for Supersymmetry, extra dimensions and associated dark matter production The number of models and amount of parameter space ruled out is remarkable March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 27

Searching for Dark Matter with AstroPhysics Look for dark matter annihilation –Produce photons or other SM particles? Excess of data at ~3.5 keV in multiple experiments has sparked interest Can the backgrounds be trusted? March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 28 E. Bulbul et al, arXiv:

Some Sources of Dark Matter are Cheap Our Sun is Moving through our Galaxy… Lots of Dark Matter is hitting the Earth every second March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 29 You are here

Dark Matter Searches with the CDMS Experiment Place Superconducting detectors deep underground Small interaction with a dark matter particle raises the temperature, which changes the resistance, which changes the voltage, which we can measure! –Currently taking data at Soudan mine (Minnesota) –Major upgrades underway  Sudbury Neutrino Observatory (SNOLab) March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 30

Direct Dark Matter Detection Experiment (artist in training conception) March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 31 Dark Matter Particle Atom in Detector Low Temperature Detector Ping We saw it! Eureka! TrHv6vlQ&list=UUvtJz9MYn_lxD4Fd4oTpugQ

Limit Plots from Dark Matter Best limits from LUX at high mass and CDMS at low mass –A little from DAMIC Next generation of experiments will have LZ (combination of LUX and Zeppelin) move sensitivity downwards, and CDMS will move to lower masses and lower cross sections Both will near the neutrino “floor” with their next round of data March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 32

Conclusions It’s an incredibly exciting time to be a scientist! There is a very real possibility that Astronomy, Cosmology and Particle Physics are all coming together at the right time Perhaps we understand the role of Dark Matter in the Universe since the Big Bang! If our understanding is correct, a major discovery may be just around the corner! March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 33

Back up slides… March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 34

Abstract High energy physics, and the search for new particles, is in a golden age. With the LHC turning on soon, and ample evidence from telescopes and other astronomical observations that dark matter is likely to be a fundamental particle, a major discovery may be just around the corner. Cosmology may also provide important clues about how this elusive particle was created in the early universe. While there are many current ways in progress to detect it, and determine its nature, none have been successful. In this talk, I’ll take a step back and share thoughts on these searches since every so often it’s useful to consider what we don’t know, and what we know for sure that just ain’t so. March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 35

March 2015 Texas Tech Colloquium David Toback Cosmology and Particle Physics 36

The Collider Program The Collider Program, Tevatron and LHC, try to address many of these questions LHC has taken over in many ways, especially for interactions which are only probed at the highest energies Tevatron is completing its studies in a number of competitive areas –Typically complementary to the LHC and other experiments Dec 2014 David Toback, Texas A&M University Fermilab Wine & Cheese – CDF Legacy Results 37

David Toback, MSC Bethancourt Lecture 38 Interested in learning more? Physics department now offers a course entitled “Big Bang & Black Holes” (ASTR/PHYS 109) –Covers Stephen Hawking’s “Brief History of Time” –Origin and Evolution of the Universe –How do stars form? –What is Dark Matter? Dark Energy? –What are Black Holes? –More on General Relativity, Quantum Mechanics and Particle Physics –Has a lab (if you want) and can be used as a Tier 2 Science Distribution credit –There is an option to take is an Honors class October /

Overview of the Talk 39 Will talk about some of the most exciting questions in all of science one-by-one: What IS Dark matter and what is some of the evidence for it? What is the Big Bang Theory? What does Dark Matter have to do with the Big Bang and the evolution of the Universe? What are scientists doing today to discover Dark Matter? Final Thoughts October 2014 David Toback, MSC Bethancourt Lecture

40 Sparticle Masses in mSUGRA In a typical mSUGRA scenario Squarks and gluinos are heavy 1st and 2nd generation squarks are mass degenerate The lightest neutralino is the LSP Dark Matter candidate m 1/2 September 2014 David Toback, Arnowitt Fest Need complementary searches for low tan  and high tan  For large values of tan  Stop, Sbottom and Stau can get much lighter  Can also have a significant effect on the branching ratios

David Toback, MSC Bethancourt Lecture October Aerial View of the LHC CMS ATLAS 27 km in Circumference! One of the largest and the most complex scientific instrument ever conceived & built by humankind p p Collides high energy protons Two huge detectors Lake Leman Geneva Airport

David Toback, MSC Bethancourt Lecture 42 How does it do it? Accelerates protons to REALLY high energies, then bashes them together October ks/Video/particle_event_full_ns.avi

Conclusions Mitchell Institute physicists effectively use the Brazos cluster for our High Throughput needs –More disk would be good, but the ability to get data here quickly has ameliorated that (and been the envy of our colleagues) –More CPU/Supercomputing would be good, but the ability to accept jobs from the GRID is more important; running opportunistically has worked fine –The amount of red tape to get jobs in, and allow our non-A&M colleagues to run, has been significant (but not insurmountable) Bottom line: Been happy with the Brazos cluster (thanks Admins!) as they helped us discover the Higgs Boson Looking forward to when the LHC turns on in March! Jan 2015 Big Data Workshop David Toback Big Computing and the Mitchell Institute for Fundamental Physics and Astronomy 43

Dark Matter 44 What is some of the evidence for Dark matter? September 2014 David Toback, AESS Seminar

What is Dark Matter? 45 October 2014 David Toback, MSC Bethancourt Lecture

The Known Particles 46 –No known particles have the properties of Dark Matter –Other reasons to believe there are new fundamental particles to be discovered –For example, we just discovered the Higgs Boson –Maybe Dark Matter is a New Particle ! October 2014 David Toback, MSC Bethancourt Lecture