The Subatomic Cosmos and the Tools of Discovery

1. The Subatomic Cosmos and the Tools of Discovery • Introduction • The Standard Model: • The cast of characters • The Forces • The new periodic table • Physics/detectors at an e+e- particle accelerator • The energy frontier: The LHC (a proton-proton collider)

2. The Cosmos A lot of recent excitement over our new view of the Universe WMAP Data: Cosmic Microwave Background The tools are sophisticated telescopes which look at EM waves inthe microwave region. The CMB is a fundamental prediction of ~any Big Bang Model Doppler shifting of atomic spectral lines indicate galaxies are rotating fasterthan they should based on the “visible mass”  Dark Matter

3. What are the Subatomic Cosmos CellularBiology ~10-5 m Chemistry ~10-8-10-10 m Nuclear Physics ~10-15 m ParticlePhysics ~10-18 m

4. Under closer examination of atoms… • There is overwhelming evidence that protons and neutrons are not “fundamental”. • They are in fact made up of smaller objects, called quarks. • Like an atom has valence electrons, a proton (or neutron) also contain “valence” quarks of two types: up(Q=+2/3e) and down (Q=-1/3e) • We know this by smashing particles together at high energy (momentum), asl = h / p  The smaller the deBroglie wavelength  better “resolution” to “see” internal structure

5. The Cast of Characters Many experiments have shown that there in fact more than justtwo types of quarks. In fact experiments have shown that: 1 2 3 u c t +2/3e -1/3e d s b 3 families of quarks… why? Ordinary matter is made of only the lightest quarks (u & d); why? How do we know about the heavier quarks, if they’re not containedin ordinary matter?

6. E=2Ee Ee Ee e- e+ How do we produce the heavier quarks E = mc2 • The electron and anti-electron (positron) can annihilate into pure energy (i.e., a photon) • This energy then can “re-emerge” in the form of any particle-antiparticle which: • satisfies energy conservation • Carry electric charge

7. Did you say anti-electron? x x x x x x Largercurvature on top particle moving upward.Charge is positive!e/m same as electron! • Antimatter is just as real as matter • Every particle has an antiparticle? • If this is so, where is all the antimatter? x x x x x x x x x x x x x x x x x x Lead

8. “50,000 atoms of anti-hydrogen made” Physicists have made 50,000 atoms of anti-hydrogen, the antimatter counterpart of normal hydrogen. This new substance will enable them to test one of the fundamental assumptions of modern physics - the Standard Model… Nature: Sept. 2002 More on Antimatter … Does matter differ from antimatter? From Big Bang, we expect: Nmatter = Nantimatter Then why is our Universe matter-dominated? What happened to all the antimatter?We hope to shed some light on this!

9. Are there more fundamental particles? • Quarks from one class of particles. • How does the electron fit into the big picture? • Like quarks, years of experiments have shown that there are 3 “electron-like” charged particles: e±, m±, t±. • Many experiments have shown that apart from their masses, the “muon”and “tau” behave identically to the electron. Again 3 families… • A third type of massless, zero-charge particle, called the neutrino, was hypothesized to exist by Fermi based on the apparent failure of momentumconservation in the decay: n  p + e- ( + n ) e- m- t- Neutrino was not detected • In 1956, Reines and Cowan discovered this elusive particle. • In act, over the last few decades, we’ve learned that |there are 3 types of neutrinos. ne nm nt

10. Electric Charge +2/3 -1/3 0 -1 The full cast of particles • 3 families of quarks • 3 familes of “leptons” • All these particles havecorresponding antiparticles

11. How do particles interact with one another?

12. P2 P1 P2 Eg, pg E2, p2 E1, p1 E2, p2 P1 P1 P2 E1-Eg , p1-pg E1-Eg , p1-pg E2+Eg , p2+pg The Modern View of Forces • Forces are the result of an INTERACTION between two objects • Interaction occurs via the exchange of a “force carrier” or “mediator”. This provides an EXTREMELY successful descriptionof subatomic phenomena. • The basic idea is as follows • Particles 1 and 2 exchangeenergy and momentum • Whallah ! An interaction !!

13. Force Carriers The application of this concept of force carriers is inherently tiedto quantum mechanics. For E&MQuantum Theory + Electromagnetism == Quantum Electrodynamics (QED) • Basic underlying concepts: • Each fundamental force has an associated force carrier. • The force carrier can only interact with particles which have theintrinsic property associated with that force. • For EM: • the force carrier is the photon (g). • the intrinsic property is electric charge. • the photon cannot “see” particles which have qe= 0. • So which particles can interact electromagnetically? • Quarks and charged leptons (but not neutrinos)

14. Strong Force QED describes atomic data toexceedingly high precision (~10-12) The electrons stay bound to the nucleusvia the continual exchange of (virtual)photons between the protons and electrons. But why does the nucleus stay together ??? The protons should repel and the nucleus should not stay intact if they only interactedvia EM ! There must be a much stronger force at workhere !! The STRONG FORCE Strong Force (QCD): Force carrier: “Gluon” Intrinsic Property: Color (r, g, b) Which of the fundamental particles have the property called “color”? Only quarks have color.  Only quarks may participate in the strong interaction !

15. Are there any other forces? Yes, one more that we know about(besides gravity) • Earlier, we mentioned that there exist heavy quarks, such as strange (s), charm (c), bottom (b) and top (t). • Why don’t we see them around today? • They’re unstable and decay rapidly (~10-9–10-12 s) • How does this happen? • Here, a third force is at work: WEAK INTERACTION • What are the force carriers and the “intrinsic charge”? • There are 3 force carriers:W+, W- and Z0 • Unlike the photon and gluon, these force carriers are very massive (~100*mP) • The intrinsic charge is called “weak charge” (sorry, not very imaginative) • It is this very large mass which accounts for the “weakness” of the weak force.

16. Weak Force The weak force is distinct from EM and STRONG. It is responsible for the decay of the heavy quarks to lighter quarks. But, the theory of the WEAK INTERACTION includes a smalldisparity between the interactions of particles and antiparticles. Understanding the differences between particles and anti-particles may lead us to an understanding of why the Universe which (presumably) started out with an equal amount of matter & antimatter, is now predominantly matter. Several experiments are taking data now and future experiments planned to explore the differences between matter and antimatter.

17. Virtual particles/Range of Force It is “easy” to show that in the exchange of a single forcecarrier, you cannot satisfy energy & momentum conservation ! Hey, that’s OK.. As long as it happens very quickly, in a time less thanDt ~ h/DE.In that time, the force carrier can travel a distance, d ~ hc /DE ~ hc / M Werner Hesienberg 1901 - 1976 • So, the range of the EM force is infinite in range because Mg=0. • The WEAK force is short range because MW,Z is very large. • The strong force is “freaky” in that Mgluon= 0, but still has very short range (~ operates on scale of the nucleus). Why ?

18. Self Interactions A photon can only interact with objects which carry electric charge. Since Qg=0, it cannot interact with other photons BUT, gluons DO CARRY COLOR CHARGE, and therefore Gluons can interact with other gluons via the strong force This is a dramatic difference between EM and the STRONG force,which is the root of the short range of the strong force. The results of this is that the proton isa complicated bag of valence quark, gluonsand even virtual quark+antiquarks

19. Quarks, Baryons & Mesons • Quarks combine to form “color neutral”particles:1 RED + 1 BLUE + 1 GREEN = COLORLESSWhen combined this way  baryons Can quarks combine in any other way to form a color neutral object? Mesons contain 1 quark + 1 antiquark The quark has “color” and the antiquark has “anticolor”(hard to show anticolor) Does this mean that quarks are actually green, red or blue? No ! It’s just a way of expressing that the intrinsic property has 3 values. Gluons interact with quarks b/c they have color charge.

20. Matter ! The Standard Model • 6 types of quarks • 6 types of leptons • 4 Fundamental Forces Exchange of force carriers == Force

21. Accelerators & Detectors • Accelerator: Aim is to produce beams of particles which aresubsequently brought into collision. • Three key factors: • What types of particles to accelerate (p, p, e+ e-) • Beam energy  Create new particles (E = mc2) • Luminosity: To “see” rare events, need a lot of collisions! • Detector: Reconstruct as much as you can about the remnants of the collision (like a detective collecting clues!) • Trigger: Can’t record all collisions; reject “uninteresting” ones and keep (save on a disk) the interesting ones. • Detectors: • Reconstruct momentum of all particles and identify them.(p, e, p, K, m, g) • Specialized detectors surrounf collision region to measuremomentum and determine particles’ identities.

22. Tunnel CLEO-c Rate for e+e- hadrons y(3770): cc bound state ZD DriftChamber CLEO-c • Collide electrons into positrons. • Each beam has energy ~ 2 GeV e - e+ Copious source of D mesons:

23. Why study D Mesons Excellent probe of the weak interaction. Recall heavy quarks decay via the weak interaction Also probes the strong interaction, since there are quarks involved.(Perturbation theory not applicable here. Unlike QED, in which aEM~1/137, as is not small at low energy) WeakInteractioncse+ne e Example of a Weak DecayD+  K0e+ne e+ W+ c Gluonicinteractionsbetween thequarks

24. CLEO-c Detector • The CESR optics are tuned to producea collision between the e+ and e-in the center of the CLEO magneticspectrometer. • Detector formed as concentricbarrels of subdetectors. • Charged particle tracking • drift chamber • Particle identification • dE/dx • Ring Imaging Cherenkov (RICH) • Reconstruction of EM showers • Identify: p0gg, hgg • Muon system: identify muons • Solenoid for measuring momentum. e - e+

25. Chargedparticle Outer Drift Chamber Reconstruct the helicaltrajectory using patternrecognition software (ie., connect the dots!) Particle’s charge and momentum determined from the curvature: Chamber filledwith He-Propane gas (60:40) p = qBR Electrons drift toward sense wireV= +2000 V • Position Measurement • vdrift~25 mm/ns (~constant) • Large multiplication near wire E ~ 1/r (Gauss’ Law) • Distance from wire (d) d = vdrift x time • Collected charge • Total Q #primary ions • Total Q different for p, e, p, K, m (particle identification) Sense Wire Field Shaping Wires Measuure

26. Inner Drift Chamber (ZD)

27. UV photons liberate electrons in TEA gas.Collected using a wirechamber LiF Radiator Ring Imaging Cherenkov Detector Aim: Particle Identification - When v>c in a medium, Cherenkov radiation (photons) are emitted: cos qc=1/bn, where b = v/c = p/(p2c2+m2c4)  If you measure qc,  “compute” m  Particle ID ! Designed/built atSyracuse

28. RICH Construction

29. RICH Performance True Kaons True Pions Before RICH # of detected photons After RICH qc(RICH)- qc(exp) (mrad)

30. CsI Calorimeter CsI crystal: Inorganic scintillator When a photon enters the crystal, because of it’s high Z, the photon “converts”: ge+e- Then, each electron will “radiate” a photone-(+)  e-(+) g The process continues again & again  EM shower Photodiodes couples to the back of the crystal detect the photons.The total number of photons produced is proportional to the incident energy.

31. Example event (DATA)e+e-y(3770)DD ElectromagneticShowers End view of detector Charged particlesreconstructed indetector Note that the charged particles are bending, as the entire detector is in a magnetic field (B into page)

32. Reconstructed D Mesons in CLEO-c K- p+p0p0 K-p+p0 K-p+ KSp+ p- p0 KSp+p- K- p+p+p- MBC K-K+ p-p+p0 KSp0 D Mesons decaying in 9 different ways (there are many more!!)

33. The Collider of the Future - LHC E = mc2 ~6 miles KEp = 7,000,000,000,000 eV Mp = 1,000,000 eV Depth ~50-150 m

34. A View of ATLAS Atlas, CMS will look to produce new forms of matter.The energy of the collision, which is very high, can be transformedinto mass

35. A collision at the LHC (ATLAS) 27 km

36. Aim: Discovery/Search for New Physics using B ( bq ) mesons The LHCb Detector p p VELO

37. The LHCb Vertex Locator Beam pipe

38. Particles passing through VELO

39. Summary • Over the last 100 years, we’ve been probing deeper & deeper into matter. • A successful description of data is provided by the Standard Model, but it can’t be the end • Many questions remain unanswered though: • Where did all the antimatter go? • What is the dark matter? It may bea particle yet to be observed! • How do particles acquire their masses ? • Do the forces unify at some high energy scale? • How does gravity fit into this picture? • Why do we have 3 families of particles withthe observed mass patterns? • We hope that some of these questions will be answered when the LHC turns on in 2007-8.. Stay tuned ! p p

40. CLEO-c ZD DriftChamber CLEO-c • Collide electrons into positrons. • Each beam has energy ~ 2 GeV If there exists a particle which hasthe same quantum numbers as thephoton, and its mass is aboutequal to the collision energy, there isa significant probability that thephoton can “transform” into thisparticle. Copious source of D mesons: y(3770)

41. K p d p Collected Charge versus Momentum • Amount of ionization depends on b=v/c, andcharge of particle. • Measure ionization indrift chamber • p/K separation to 0.7 GeV • p/p separation to 1.3 GeV • K/p separation to 1.3 GeV