Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 248.882 LHC PhysicsExperimental Methods and MeasurementsOnia as Probes in Heavy Ion Physics[Lecture 10, March 9, 2009]C.Paus, LHC Physics: Onia as Probes in Heavy Ion Physics 2Lecture Outline Onia as Probes in Heavy Ion Physics●what are onia? and bit of history●why are they interesting in heavy ion physics?●what can we do with them in High Energy physics?●production and their decay●general reconstruction of oniaC.Paus, LHC Physics: Onia as Probes in Heavy Ion Physics 3Positronium Started it All Positronium (lives ≈100 ns, discovered 1951 by Martin Deutsch, MIT)●quasi stable system of electron and positron (exotic atom)●decays to n photons (more than 1, spin argument 2 vs 3)●compares closely to hydrogen atom: energy levels (Bohr)●difference to hydrogen: reduced mass (m*)h – Planck's constantqe – electron chargeε0 – electric constant●plugging in the numbers we findC.Paus, LHC Physics: Onia as Probes in Heavy Ion Physics 4Charge Shielding in Plasma Debye length●defines distance over which mobile charge carriers shield out electric fields in a plasma (for colder ions)Te – electron temperatureε0 – permittivity of free spacene – electron density Charge becomes invisible to outside●positronium is nothing but a dipole●charge screening should affect positronium in a plasma●modified energy levels (high energy levels disappear first)●for high enough densities it should even disappear all togetherC.Paus, LHC Physics: Onia as Probes in Heavy Ion Physics 5(Quark)Onia Flavorless meson: quark and its own antiquark●only heavy quarks (c, b, (t)) are relevant, because light quarks all mix together because of similar masses●charmonia: J/Ψ, Ψ', Ψ'' etc. are from: ●J – Brookhaven fixed target experiment (S.C.C. Ting, MIT)●Ψ – SLAC e+e-- experiment (B. Richter, SLAC)●November Revolution: 1974, Nobel prize 1976●lifetime: 0.72 x 10-20 secsC.Paus, LHC Physics: Onia as Probes in Heavy Ion Physics 6(Quark)Onia Flavorless meson: quark and its own antiquark●bottomonia: Upsilon(1S, 2S, 3S, 4S) etc. are from: ●Upsilon – E288 FNAL experiment (L. Lederman, Columbia)●discovered in 1977●lifetime: 1.21 x 10-20 secs●toponium doesn't exist, too short livedC.Paus, LHC Physics: Onia as Probes in Heavy Ion Physics 7Theory of Onia Theory predicts properties of Onia●most importantly the masses●very difficult because it is the typical example for the non-perturbative regime of QCD●next order might be larger then the preceding one●only general method (first principles) is lattice gauge theory●speed of heavy quarks in onia small (0.3c for charmonia, and 0.1c for bottomonia)●expand is orders of β and use for lattice (Non Relativistic QCD = NRQCD)●some approximate theories work surprisingly well though●effective potentialsC.Paus, LHC Physics: Onia as Probes in Heavy Ion Physics 8Effective Theory of Quarkonia Use non relativistic potential theory (not exact)●Schroedinger equation: ●Cornell potential: Coulomb potential, coupling, a ≈ π/12confining string tension: b ≈0.2 GeV2 Quarkonia masses, mi, and radii, riC.Paus, LHC Physics: Onia as Probes in Heavy Ion Physics 9Account of Quarkonia Masses Summary from potential models** lifted from talk by Hans Satz at http://hp2006.lbl.gov/source/program.htm ΔE – binding energy ΔM – mass difference observed with predictionC.Paus, LHC Physics: Onia as Probes in Heavy Ion Physics 10Relevance of Onia in HEP and HI Onia in High Energy Physics●defined new era of HEP●quark constellation formed around J/Ψ, 1974 (u,d,s to [u,d], [c,s])●family model emerged●discovery of the third family, 1977 ([t,b]) with the Upsilon●started long search for the top quark (TeVatron 1994)●onia production and spectroscopy (NPQCD) Onia in Heavy Ion Physics●naïve consideration of Debye screening analogy in quark gluon plasma●onia form a simple color dipole●high excited states disappear first●finally onia disappear all togetherC.Paus, LHC Physics: Onia as Probes in Heavy Ion Physics 11Recent Excitement in Spectroscopy In the last 4 years spectroscopy had a revival●penta quarks (observations 2003 turned out not to be real)●very interesting example how things can go wrong in spectroscopy●typical 'observation' plot .. and statistics of observation/null results●penta quarks: particles containing 5 quarks (meson 2, baryon 3 ...)●new excited states of the Ds meson●excited charmonia or new types of matter? Observations are real but what do they represent? ex. X(3872) followsmasseventsC.Paus, LHC Physics: Onia as Probes in Heavy Ion Physics 12Overview of Charmonia Usual complex picture of energy states●xDy candidates are next to be tackled●mass predictions are at 50 MeV level, but not rock solidC.Paus, LHC Physics: Onia as Probes in Heavy Ion Physics 13Observation of the X(3872) In August 2003 Belle announced●looking for the next charmonium state (3D2)●new particle at energy ≈ 3872 MeV in decay to J/ψ π+π--●confirmed very shortly afterwards at CDF Search strategy at Belle (e+e--)●in decay B+ → J/ψ π+π-- K+●events: 35.7 ± 6.8 10.3 std. deviations●mass: 3872.0 ± 0.6 ± 0.5 MeV●width: smaller 2.3 MeV (90% CL)●is this a charmonium?C.Paus, LHC Physics: Onia as Probes in Heavy Ion Physics 14Nature of the Particle: What is it? Coined the X because of its unclear nature●obvious candidate: excited charmonium but mass different●mass very close to DD* thresholdhypothesis of DD*moleculeBig deal: new type ofbinding – QDCC.Paus, LHC Physics: Onia as Probes in Heavy Ion Physics 15CDF Charmonia Look at charmonia at the TeVatron●classic example is J/ψ→μμ: prompt versus B → J/ψX●B longer lived so J/ψ is displaced: ≈20% from B Muon decay is crucial●muons are clean (lecture 11)●trigger is simple and low rate Separate prompts●use silicon detector●achieve statistical separation One of standard candles for calibrationsC.Paus, LHC Physics: Onia as Probes in Heavy Ion Physics 16CDF Observation of X(3872) Combinatorics the killer●most X(3872) expected prompt●clean J/ψ→μμ but two more pions: X→J/ψπ+π-- many possibilities●restrict phase space: pT, angles●calibrate with: ψ' → J/ψπ+π--●almost same kinematics Analysis