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Why is there mass in our universe ?

Why is there mass in our universe ?. Azeddine Kasmi* *Lightner-Sams Fellow Physics Department Southern Methodist University. Some History of Physics. Particle Physics and the Standard Model. Coffee Break The Large Hadron Collider (LHC). Potential discoveries using the ATLAS detector.

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Why is there mass in our universe ?

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  1. Why is there mass in our universe ? Azeddine Kasmi**Lightner-Sams FellowPhysics DepartmentSouthern Methodist University AZEDDINE KASMI QuarkNet talk

  2. Some History of Physics. Particle Physics and the Standard Model. Coffee Break The Large Hadron Collider (LHC). Potential discoveries using the ATLAS detector. AZEDDINE KASMI QuarkNet talk

  3. Early Elementary particles pioneers • What is the world made of ? • and what holds it together ? In ancient times, people tried the combination of 4 components: Air, Water, fire, Earth The Greek philosopher Democritus (460 BC – 370 BC) introduced the notion of the atom. AZEDDINE KASMI QuarkNet talk

  4. Classical Physics and Relativity • Gravitation is a natural phenomenon. • allows objects with mass attract each other. • Keeps planets in orbits • Gravity acts immediately Isaac Newton(1643-1727) • Speed of light is the speed limit • Light does not travel instantly. And God said ...and there was light. James Clerk Maxwell (1866-1870) AZEDDINE KASMI QuarkNet talk

  5. Classical Physics and Relativity Mass–Energy Equivalence • 3D of space and 1D of time as bound together in a single fabric of space time. • This fabric of space-time is stretched by heavy object. • Curving of that space-time is what we feel as gravity. • Earth stays in orbit because it follows the curvature in the space-time caused by the sun presence. Albert Einstein (1915) If Sun disappears No change in orbit until the wave reaches Earth Gravitational disturbance forms a wave AZEDDINE KASMI QuarkNet talk

  6. Quantum Mechanics 1920’s • Quantum mechanics : • the study of mechanical systems whose dimensions are close to or below the atomic scale. • Explains why Classical Mechanics failed to explain • radiation by heated bodies • stable atoms • Heisenberg uncertainty principle • It’s impossible to measure simultaneously the position and momentum of a particle. W. Heisenberg ( in 1932) Dp Dx • In QM all what we can do is find the probability of finding a particle in a given state. AZEDDINE KASMI QuarkNet talk

  7. The cop says: Do you have any idea how fast you were going back there ? Driver answers: No Cop: Crap ! Me neither No speeding tickets in the quantum world ! AZEDDINE KASMI QuarkNet talk

  8. Special relativity + Quantum Mechanics = Antimatter Detective story about a secret society which ... ... steals 1 g of antimatter from a place called “CERN” ... to blow up the Vatican, an old “enemy of science and CERN”. Paul A.M. Dirac (1928) What made CERN Popular Movie, May 2009 Every particle has its antiparticle with same mass but opposite charge Particle and its antiparticle annihilates AZEDDINE KASMI QuarkNet talk

  9. Reductionism SLAC(1968): Quarks discovery Chadwick(1932): discovers neutron Most of the particles that were taught to be elementary turned out to have constituents Rutherford: Nuclear atom (proton) Thomson (1897): Electron discovery AZEDDINE KASMI QuarkNet talk

  10. The forces in nature Think of forces as interaction Two particles interact by exchanging a messenger particle. Exchanged particle transfers momentum from one interacting particle to another. AZEDDINE KASMI QuarkNet talk

  11. The Standard Model (SM) of particle physics The SM describes interactions between the elementary particles that make up all matter. To date, the SM agrees well with experiment. Last confirmation Top quark discovery (1995 Fermi Lab) The building blocks of matter are fermions Force carriers are bosons AZEDDINE KASMI QuarkNet talk

  12. The origin of mass ? The Standard Model proposes: another field not yet observed. indistinguishable from empty space. This is known as the Higgs field. All space is filled with this field, and that by interacting with this field, particles acquire their masses. The Higgs field has at least one new particle associated with it, the Higgs particle (or Higgs boson). The ATLAS detector at the LHC will be able to detect this particle if it exists. This would be one of the greatest scientific discoveries ever! AZEDDINE KASMI QuarkNet talk

  13. The Higgs mechanism ! To understand the Higgs mechanism, imagine that a room full of physicists chatting quietly is like space filled with the Higgs field ... ... a well-known scientist walks in, creating a disturbance as he moves across the room and attracting a cluster of admirers with each step ... ... this increases his resistance to movement, in other words, he acquires mass, just like a particle moving through the Higgs field... It should be probably a Hollywood star as who cares about a scientist ! AZEDDINE KASMI QuarkNet talk

  14. Spontaneous Symmetry Breaking The symmetry is broken here As the birds have chosen one direction There is symmetry All directions look the same AZEDDINE KASMI QuarkNet talk

  15. Ferromagnet analogy • At low temperature, the iron atoms will align themselves • Despite no direction preferred in interaction between atoms • Therefore, atoms acquire certain energy. • i.e. must add heat to break the alignment. • Lowest energy state of universe • Non zero Higgs field • Generates mass for W,Z AZEDDINE KASMI QuarkNet talk

  16. Spontaneous symmetry breaking illustrated by the horse and the carrot 1 2 3 4 AZEDDINE KASMI QuarkNet talk

  17. Conclusion on Spontaneous Symmetry Breaking The Standard Model relies on the process of spontaneous symmetry breaking to generate mass to the elementary particle. Without it, the elementary particle would indeed remain massless. When applied to particle physics, it leads to the production of a scalar particle named the Higgs boson. Mexican hat potential AZEDDINE KASMI QuarkNet talk

  18. What we know so far in the universe • The SM is not a complete theory of fundamental interactions for the following reasons. • The lack of inclusion of gravity. • Incomplete description of why particles have mass. • We are surrounded by: • Dark Matter • or unseen matter. • Dark Energy • Tends to increase the expansion rate of the universe. SM AZEDDINE KASMI QuarkNet talk

  19. Evidence of what we do not know yet Rotation curve of a typical spiral galaxy Evidence for Dark Matter Rotational speeds of galaxies B. Observed A. Predicted by Newtonian dynamics • Evidence for Dark Energy • Supernovae • Redshift tells us how fast it receding • Standard candles (object with extreme consistent brightness e.g. Supernova Type la) are used to measure the distance. • Expansion of the universe accelerates. Multiwavelength X-ray image of SN 1572 or Tycho's Nova, the remnant of a Type Ia supernova. (NASA/CXC/Rutgers/J.Warren & J.Hughes et al.) AZEDDINE KASMI QuarkNet talk

  20. Grand Unification theory GUT 1864: J.C.Maxwell Unified Electricity and Magnetism. Electromagnetism 1973: Salam and Weinberg Unification of the electromagnetic and weak interactions. W, Z bosons AZEDDINE KASMI QuarkNet talk

  21. Coffee Break AZEDDINE KASMI QuarkNet talk

  22. To test a theory you need an Accelerator, Detector, and Cafeteria LHC PROTONS: 99.9999991 per cent of the speed of light 11000 times per second circling the 27 km ring AZEDDINE KASMI QuarkNet talk

  23. General view of the LHC and experiments AZEDDINE KASMI QuarkNet talk

  24. The Large Hadron Collider (LHC) One Higgs per Hour 10-4Hz AZEDDINE KASMI QuarkNet talk

  25. ATLAS collaboration http://atlas.ch Philippe has a good coffee maker ($1.5) PEOPLE SIZE AZEDDINE KASMI QuarkNet talk

  26. ATLAS detector vs. Foundren science building Length 46 m Height 25 m Overall weight 7000 Tons AZEDDINE KASMI QuarkNet talk

  27. General Principle for particle detection Visible particles are measured by the various subdetectors and identified from their characteristic pattern . AZEDDINE KASMI QuarkNet talk

  28. ATLAS: The Technical Challenges • ATLAS major components • The Inner Detector • 350000 particles/ mm2 s makes the radiation • hardness a top priority. • Transition Radiation Tracker • The Calorimeters • The Muon Spectrometer • Solenoidal and Toroidal Magnets • Data acquisition and Couputing 80 M rectangular pixels TRT Hundreds of thousands of gas-filled straws at high voltage, each with a wire down its axis Central Selenoid: 5 tons coil contains 9 km of superconducting wire cooled by liquid helium, I = 8000 Amps, B = 2 T AZEDDINE KASMI QuarkNet talk

  29. Electromagnetic Calorimeter (EMC) The calorimeter consists of thin lead plates (about 1.5 mm thick) separated by sensing devices. The lead plates are immersed in a bath of liquid argon. The liquid argon gaps (about 4 mm) between plates are subjected to a large electric field. AZEDDINE KASMI QuarkNet talk

  30. How does the EMC work ? • When the electron shower gets into the argon, it makes a trail of electron-ion pairs along its path. • The electric field causes the electrons (from the Argon) to drift to the positive side. • This produces an electric current in an external circuit connected to the calorimeter. When a High energy photons or electrons traverse the lead, they produce an electron shower. AZEDDINE KASMI QuarkNet talk

  31. Muons detections • Muons are the only charged particle that can travel through all of the calorimeter material and reach the outer layer. • much less affected by the electric forces of the atomic nuclei that they encounter (200 times more massive than electrons). • Do not produce same kind of electromagnetic shower of electrons. • Energy loss via electron-ion pairs along their path. • in case of steel or copper, 1 MeV per millimeter of path. • Example a muon of 5 GeV • penetrate about 5 meters of steel. • Thus energetic particles seen outside the hadron calorimeter are guaranteed to be muons. Monitored Drift Tubes Gas-filled 3 cm tube AZEDDINE KASMI QuarkNet talk

  32. Selection of events Trigger System Level1 Trigger decision  less than 2ms larger than interaction rate of 25 ns Of 40 M bunch crossings per seconds, less than 100000 pass Level-1 Level2 Analyses in greater detail specific regions of interest identified by Level 1. Less than 1000 events per second pass Level2 Level3 Less than 100 events per second are left after Level3. These events are passed on to a data storage system for offline analysis Interaction rate: ~ 109 events/s Can record ~ 200 events/s (event size 1 MB) AZEDDINE KASMI QuarkNet talk

  33. LHC will be completed in 2008 and run for the next 10-15 years Experiments will produce about 15 Millions Gigabytes per year of data (about 20 million CDs!) LHC data analysis requires a computing power equivalent to around 100000 of today’s fastest PC processors Requires many cooperating computer centers, as CERN can only provide the 20% of the capacity. SMU is part of the grid Balloon (30 km) CD stack with 1 year LHC data! (~ 20 Km) Concorde (15Km) The Grid Mont Blanc (4.8 km) AZEDDINE KASMI QuarkNet talk

  34. What’s an event ? The occasion of two elementary particles colliding (or a single particle decaying) This is NOT Higgs and yet it repeats every 25 ns ! 40M/s It’s just a junk 10-9 of that is a Higgs Higgs  ZZ*  2e + 2m + jet After some cuts AZEDDINE KASMI QuarkNet talk

  35. Data Analysis and statistics H1 H1 H1 The situation is similar to searching for a needle in a stack of hay Fortunately, the characteristics of signal (Higgs) event are different from those of a background. AZEDDINE KASMI QuarkNet talk

  36. Missing Energy in case of WZ n • No net momentum into reaction • But summing 3e gives net momentum out • Vector Addition • Neutrino momentum would the missing Energy • Conservation of Momentum. e- e- e- • Thus, a huge missing Energy will characterize the background event. • So, the missing Energy can be used as a veto WZ  3e + n AZEDDINE KASMI QuarkNet talk

  37. What’s the plan Understand ZZ, ttbar, (SM) Higgs searches AZEDDINE KASMI QuarkNet talk

  38. Higgs production AZEDDINE KASMI QuarkNet talk

  39. Higgs decay to a 4 leptons channel L+ Z L- L+ Z L- Unfornately, The ATLAS detector is not perfect. Thus, a substantial leptons identification problems will occur in the 4 leptons channel @SMU we have a group that looks at events with 3 identified leptons and try to find the 4th leptons somewhere on the Detector to increase the efficiency AZEDDINE KASMI QuarkNet talk

  40. Higgs 4leptons and background The Standard Model has a limit on the Higgs mass up to 1000 GeV Experiments have ruled out low masses up to 114 GeV. My focus is on Higgs mass within the range 130 GeV -180 GeV The signal (H) will follow a Gaussian distribution and will be seen as a bump. However, the background will be as flat distribution. Note that the discovery of ZZ dibosons was made on July 25th 2008 by Fermi Lab. (only 3 events) AZEDDINE KASMI QuarkNet talk

  41. Higgs in case of a lost electron H  2m1e + X Here the non identified electron was recovered via the jet algorithm AZEDDINE KASMI QuarkNet talk

  42. The complete picture of the standard Model with the Higgs THANK YOU THE END ! Wanted AZEDDINE KASMI QuarkNet talk

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