Фундаментальные открытия и будущие проекты в физике элементарных частиц

Dmitri Denisov, Fermilab RASA-USA Meeting, November 5, 2017

Particle Physics: What Everything Around Us is Made of?

1cm

10-18cm

What is next?

2 Denisov RASA 2017 From Periodic Table to Quarks and Leptons in 50 years

Standard Model

Now we have much simpler picture how the world around us works

3 Denisov RASA 2017 Standard “Model” of Particle Physics • Standard Model of particle physics is the theory of elementary particles and their interactions • Makes everything around us of a small number of objects • Quarks and leptons • Proton is made of “uud” quarks • Electrons rotating around nucleus • Forces are carried by • photon - electromagnetic • gluons - strong • W/Z bosons - weak • Higgs boson provides mass • Each particle has “anti-particle” • Many questions remain – Exactly the same mass, spin… but – Why 3 types of quarks and leptons? opposite electric charge – Why no free quarks? • Some particles are unstable and decay – Why gravity has no effect in sub- within a fraction of a second atomic world? • Can calculate processes in sub-atomic world – Why we see very little anti-matter to a very high precision around us? • Better than 10-10 4 Denisov RASA 2017 Why High Energy and Why Colliders Cell Accelerators are built to study the Nature smallest objects

The de Broglie equation Wavelength = h/E

Proton ~2 .10-18 cm for highest energy accelerator today

Accelerators are giant microscopes!

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Why High Energy and Why Colliders Cell

Accelerators convert energy into mass

E = Mc2

Ebeam MassProton Ebeam Objects with masses up to

Mass = 2Ebeam could be created

Collider center of mass energy is 2Ebeam instead of √(2mEbeam) for fixed target Top quark mass is 175 times above proton mass, still we could produce them colliding two protons! Accelerators are converters of energy into mass!

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Basics of Accelerators • The only practical way to accelerate elementary particles is to use electric field – Can only accelerate charged particles – 1 Volt potential provides 1 eV energy to a particle with electron/proton charge – Modern accelerators have energy in the range of 1 Tera electron Volt (TeV) • 1012 electron Volt • What types of charged particles? – Protons, electrons, muons – The rest are either live for a very short time or have no electric charge – Up to now all high energy accelerators used electrons or protons/antiprotons as beams • There are two main types of the accelerators: circular and linear • Circular accelerators – Small area of accelerating electrical field (a few meters) and then particles bended with magnets around circle to pass through the accelerating field many times (millions) – Every turn particles gets more and more energy with each turn • Linear accelerators – Long straight line with electrical accelerating structures

7 Denisov RASA 2017 Progress in Accelerators Sizes: 4 orders of Magnitude!

First ~12 cm cyclotron by Lawrence – 1930’s Tevatron near Chicago – 1990’s

8 Denisov RASA 2017 The Tevatron: start 1985 Top quark discovery

• First superconducting magnets accelerator with 2 TeV center of mass energy • Collided protons and anti-protons • Discovered last standard model quark – The top quark

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Plans to Reach Higher Energies: 80’-90’s

USSR USA

3x3 TeV, UNK 20x20 TeV, SSC

10 Denisov RASA 2017 The Large Hadron Collider (LHC) – the History in the Making

• Collide protons and protons in 27 km long tunnel at 13 TeV near Geneva, Switzerland • Discovered the last missing piece of the standard model - the Higgs boson • Extensive studies of the Nature at smallest distances and highest energies

Denisov RASA 2017 11 Colliders

of first physics • First e+e- colliders started operation in early 1960’s with hadron colliders (storage ring) first collisions in 1971 • Large number of e+e- colliders, while few proton-proton or proton-antiproton (hadron) colliders • Hadron colliders provide higher center of mass energy, while colliding “composite” particles

Denisov RASA 2017 12 How Physicists Detect Particles

• Majority of particles decays into other particles almost immediately – Detectors surround interaction region – Many layers to detect different species • Particles we study have very high energies large detectors are needed to absorb them • We are taking millions of “pictures” per second to analyze collected data “off-line”

Top quark pair production

Top quark pair production event display 13 Denisov RASA 2017 Collider Detectors In order to analyze millions of interactions per second with particles carrying kinetic energies 100’s times above their rest mass two complex detectors have been built at Fermilab

CDF DØ

Why two detectors? To verify results, to increase data sets available, and to create healthy competition

14 Denisov RASA 2017 Statistical Character of Particle Physics All studies in particle physics are subject to statistical fluctuations Probabilistic nature of results with small number of events Simulated Example

X10 data 

Increase in the data set could make “hints of a signal” obvious and statistically significant

15 Denisov RASA 2017 Scientific Collaborations Behind all technical complexity there are 100’s of scientists from all over the world working closely together excited by the challenge of pushing limits of knowledge

CDF : ~600 physicists, 15 countries, 63 institutions DØ : ~550 physicists, 18 countries, 90 institutions

16 Denisov RASA 2017 Particle Physics International Collaborations

• Physics research at Fermilab is an excellent example of productive international cooperation – ~100 publications in refereed journals per year – ~60 PhDs obtained per year

17 Denisov RASA 2017 Future Particle Physics Projects

• Particle physics field is working on designs of future colliders mainly of two types

• e+e- colliders as “factory” of W/Z bosons, Higgs bosons and top quarks • ~380 GeV in the center of mass

• Proton-proton colliders with energy ~100 TeV (x10 what is available today) to create heavy particles and study distances below 10-19 cm • Structures inside quarks or electrons? • New “universes”, like supersymmetric particles? • Dark matter creation? • Extra dimensions?

18 Denisov RASA 2017 International Linear Collider

• ILC or International Linear Collider is e+e- linear collider proposed to be hosted in Japan • Center of mass energy ~500 GeV

Denisov RASA 2017 19 Proposals for Colliders in China: CepC and SppC

• CepC – Circular electron positron Collider – ~100 km long ring – 90-250-380 GeV in the center of mass • SppC – Super proton proton Collider – In the same ring as CepC – ~100 TeV energy

Denisov RASA 2017 20 CERN’s pp 100 TeV collider

Parameter FCC-pp LHC Energy [TeV] 100 c.m. 14 c.m. Dipole field [T] 16 8.33 # IP 2 main, +2 4 -2 -1 34 Luminosity/IPmain [cm s ] 5 - 25 x 5 x 10 1034 Stored energy/beam [GJ] 8.4 0.39 Synchrotron rad. 28.4 0.17 [W/m/aperture] Bunch spacing [ns] 25 (5) 25

• CERN laboratory (home of the LHC) is planning for circular e+e- collider as the Higgs factory (380 GeV) and/or 100 TeV proton proton collider • Main challenges – Long tunnel – High synchrotron radiation load – High field magnets (proton collider only)

Denisov RASA 2017 21 Particle Physics and Technology 1980’s 2000’s

• Touch screen – in 1970’s • World Wide Web – in 1980’s • Development of supeconducting magnets for the first superconducting accelerator in1980’s at Fermilab paved the way for use of supeconducting coils for MRI • Wide use of particles accelerators and detectors in medicine and industry

22 Denisov RASA 2017 Conclusions

• Particle physics studies the laws of Nature on smallest distances – currently up to 10-18 cm

• Excellent theory, the standard model, was developed to describe sub-atomic world over last 50 years – All expected particles discovered

• All of the above achieved by large and productive international collaborations

• Future proposed accelerators are of two types – e+e- colliders as “factories” of all known particles – Proton proton colliders at the next energy frontier

• Mankind will find options to build higher energy colliders – As this is the only way to progress toward understanding What is next? of the Nature at even smaller distances

Denisov RASA 2017 23 Circular Accelerators • To keep charged particles rotating around the ring bending magnets are needed – The key element of a high energy circular accelerator

• Maximum energy of the accelerator

. – Ebeam ~ R B where R is the accelerator radius and B is bending magnetic field

• First Fermilab accelerator had energy of ~450 GeV (Giga electron Volt) with bending field of ~2 Tesla (room temperature iron magnets) – Superconducting magnets increased field to ~4.5 Tesla bringing energy of the beam to ~1 TeV (Tera electron volt – Tevatron!) – At such energy mass of the proton is 1000 times more than it’s rest mass (of about 1 GeV)

• There are two options to increase energy of a circular accelerator – Increase magnetic field in the bending magnets – Increase radius of the tunnel

24 Denisov RASA 2017 Bending Magnets

• Two main issues reaching high field – Critical superconducting current – Mechanical forces acting on coils • LHC magnets are ~9 Tesla • Current practical limit is ~16 Tesla

25 Denisov RASA 2017 Linear Accelerators

• Major challenge is to create high electric field without sparks • Usually superconducting “cavities” are used for the acceleration – To reduce energy losses • Oscillating electric field is created along beam line which accelerates particles bunches

~1 meter

. Current maximum field peak value is ~30 million Volts per meter

Denisov RASA 2017 26 Accelerators and the Standard Model

• Progress in particle physics over past 40 years was closely related to discoveries at ever more powerful colliders • e+e- colliders • c quark, tau lepton, gluon • Use of antiprotons in the same ring as protons • W and Z bosons • Superconducting magnets • Top quark and the Higgs boson • All expected standard model elementary particles have been discovered at colliders • Tau neutrino and b quark in fixed target experiment at Fermilab

At every step new accelerator ideas provided less expensive ways to get to higher beams energies and higher luminosities

Denisov RASA 2017 27 Operating or Soon to be Operating Colliders

of first physics • Single high energy hadron collider – the LHC, now at 13 TeV – RHIC at BNL – nuclear studies • DAFNE (Frascati), VEPP (Novosibirsk), BEPC (Beijing) – low energy e+e- colliders • SuperKEK-B – b-factory at KEK to restart in 2016 with ~40 times higher luminosity – Studies of particle containing b-quarks

Denisov RASA 2017 28 µ+µ- Colliders

• Muons are “heavy electrons”, they do not have high synchrotron radiation making 2x2 TeV circular accelerator viable for multi TeV energies – γ factor at the same energy is ~200 times less than for the electrons • Muons are unstable with life-time of 2.2 micro seconds – Decay to an electron and a pair of neutrinos – With γ factor of 1000, 2.2 milli seconds lifetime in the lab system -1000 km flight at a speed of light • Main accelerator challenge – To make large number of muons quickly and then “cool” them to focus into small diameter beam to collide • Another issue are decays and irradiation by electrons from muon decays – And neutrinos irradiation!

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