Physics with CMS. Panos Razis University of Cyprus

Transcription

1 Physics with CMS Outline Introduction LEP/L3 results CMS Experiment at LHC Decisive Searches at LHC Search for the higgs boson Search for supersymmetry / Dark Matter Search for Large Extra Dimensions Applications Summary Panos Razis University of Cyprus UCY HEP 1

2 Introduction: Particles and Forces 2

3 Introduction: LEP/L3 results E CM = GeV L= cm -2 s -1 B= 0.5 Tesla 3

4 Introduction: LEP/L3 results (1) Measurement of the number of Neutrino species Indirect N ν =2.9840± (all 4) Direct N ν =2.98±0.05±0.04 (L3) (2) Prediction of the top quark mass m t (LEP) = 177±11±19 GeV m t (CDF) = 174±10±13 GeV Today: m t =171.2±2.1 GeV (3) Measurement of the Z 0 lineshape M Z = ± GeV Γ Z = ± GeV 4

5 Introduction: LEP/L3 results (4) New Particle Searches M H > 112 GeV SM Higgs M H > GeV (all 4 expts) M h > 86.0 GeV MSSM M A > 86.5 GeV M H± > 76.5 GeV (5) Excited Leptons m e* > GeV m μ* > GeV m τ* > 99.9 GeV m νe* > 99.3 GeV m νμ* > 99.4 GeV m ντ* > 93.9 GeV χ 0 1 mχ 0 1 Limits on Couplings (6) Search for SUSY Dark Matter candidates Neutralino s χ 0 1, χ0 2, χ0 3, χ0 4 Lightest Supersymmetric Particle (LSP) > 32.5 GeV tanβ > 0.7 M H = GeV 5

6 Introduction: LEP/L3 results (7) Tests of QED / Study of Rare Decays Br(Z μτ ) < 19 x 10-6 Br(Z π 0 γ) < 5.2x10-5 Br(Z eτ ) < 13 x 10-6 LFV Decays Br(Z γγ) < 5.2 x 10-5 Rare Decays Br(Z eμ ) < 6 x 10-6 Br(Z ηγ) < 7.6 x 10-5 (8) Searches for unstable neutral/charged heavy leptons, 4 th generation quarks, leptoquarks, other rare decays, SUSY particles etc (9) Measurements of coupling contants, parameters, sin 2 θw, study of hadronic and leptonic physics, jets, forward physics, cosmic rays etc 6

7 Introduction: LEP/L3 results (9) Measurement of the W properties M W = ±0.046±0.031 Γ W = 2.18±0.11±0.09 (10) Running of the coupling constant as 7

8 Standard Model Electromagnetic e + γ q Electroweak u Charged Weak e - e + Neutral e + q Strong g q' e - q d W ν e e - Z o e - q q' e + e + e - ν e e + e + q q g g g g 16 γ W Z o g g e - e - u d e - e - q' q' g g g g Range, relative strength =10-2 Range ~10-18 m, relative strength ~10-14 Range ~ m, relative strength = 1 Matter particles (spin 1/2) interact via force particles (spin 1) Standard Model: internal symmetry SU(3)xSU(2)xU(1) 8

9 Standard Model Standard Model very successful Describes almost all physical phenomena to ~10-32 sec but it is an effective theory, cannot be the full story LEP1 LEP2 Z W 9

10 Problems with the Standard Model sin 2 θw, proton lifetime, many free parameters Why is electromagnetism so different than weak force? Why is the photon mass so different from the W/Z mass? Answer within SM: Higgs mechanism A field (spin-0) permeates all space; γ and W/Z couple differently Fairly elegant and economic explanation Quadratic divergence in the higgs mass Need to find the higgs boson ( p 2 ) = m 2 ( 2 Λ ) 2 + Cg Λ One of major motivations of the LHC experiments (CMS) CMS designed to discover the SM higgs within entire range of allowed masses m 2 2 dk 2 p 2 10

11 Problems with the Standard Model What is the composition of the missing mass (dark matter)? observation theory Dark matter! 2 mv GMm GM = v = 2 r r r How about dark (vacuum) energy? Huge energy density (10 54 times larger than observed the cosmological constant) 11

12 Large Hadron Collider Program CERN - LHC 27 km περίμετρος CMS Lac Leman Genève LHCb ALICE ATLAS 12

13 CERN - LHC 27 km περίμετρος Large Hadron Collider Program 13

14 CMS Experiment at LHC E CM = 14 TeV L= cm -2 s -1 B= 4 Tesla 14

15 CMS Experiment at LHC 15

16 CMS Experiment at LHC 16

17 CMS Experiment at LHC Conditions at LHC for CMS L = cm -2 s -1 High Radiation 0.18 Gy/h at n =0, 6.5 Gy/h at n =2.6 High Event Rate 40 MHz High Magnetic Field 4 Tesla Wide Dynamic Range 20MeV 2TeV Thermal/Mechanical Stresses t Varying Conditions (temperature etc.) Long Duration >10 Years 17

18 Electromagnetic Calorimeter PbWO 4 Crystals ( 26 X 0 ) LIGHT CREATION High Density Moderate Light Yield Fast Luminescence Radiation Hardness Low Production Cost Density g/cm Radiation Length cm 0.89 Moliere Radius cm 2.19 Index of Refraction (at λ=500nm) 2.30 Luminescence nm Peak Emission nm 440 Typical Light Yield p.e./mev in 1 μsec 10 Light Yield % in 25nsec 85% Temperature Dependence of Light Yield %/ 0 C

19 Electromagnetic Calorimeter Avalanche PhotoDiodes (APD s) LIGHT CONVERSION Small size (5x5mm 2 ) Fast (2ns) High Quantum Efficiency (70-80%) Small Nuclear Counter Effect Insensitive to Magnetic Field Compatible Spectral Sensitivity Internal Gain / Low Noise Sensitivity: Temperature, Bias Voltage, High Radiation 19

20 Electromagnetic Calorimeter Very Front End Electronics (VFE) ANALOG - Floating Point PreAmps (FPPA) - Gain Ranging Multiplexer (1,5,9,33) - Floating Point Sample and Hold - Voltage Sampling ADC Optical Link-Upper Level Readout DIGITAL - High Speed Data Links - Pipeline - Tower Energy sums - Interface to Trigger and DAQ Light Monitoring Systems - Q-switched Red and Green Lasers -Optical Fibers -Normalization by Si PN Diodes - LED Light Source SIGNAL PROCESSING LARGE DYNAMIC RANGE 20

21 Electromagnetic Calorimeter (a) Radiation Damage (c) Electronic Noise (e) Signal Amplification (g) Collection Time (b) Temperature and HV variation (d) Energy sharing in crystals (f) Quantum Efficiency (h) Light Yield 21

22 Search for the (SM) higgs boson 22

23 Supersymmetry For every particle in the SM, there is a super-partner with spin ½ difference In SUSY, the loops cancel naturally: Candidate for dark matter! 23

24 Supersymmetry SUSY doubles the particle spectrum must be a broken symmetry unseen till now SUSY enables the unification of the strong, weak and EM forces: 60 α α 1 α α 1 3 With SUSY Q (GeV) 8303A5 24

25 Search for Supersymmetry in CMS Many hard Jets Large missing energy 2 LSPs Many neutrinos Many leptons In a word Spectacular! 25

26 Large Extra Dimensions Number (D) of space-time dimensions form of force observed E+M: F~1/r 2 because D=3+1 For ants living in D=2+1 dimensions, E+M is actually a F~1/r force Side Conclusion: the running of the force changes in the presence of additional dimensions 26

27 Large Extra Dimensions Different models, different signatures: Channels with missing E T : E miss T +(jet/γ) (back-to-back) Direct reconstruction of KK modes (W. Z search) Warped extra dimensions (graviton excitations) 27

28 Applications Education Technology Basic Research 1. Study of the Atom Atomic Structure chemical physical properties of matter Transitions E/M radiation, spectra, lasers Electric Charge conductors, semiconductors, electronics Telecommunications, Computers, Electronic Appliances 2. Study of the Nucleus Nuclear Structure Ε-Μ Transformations Particle Radiation isotopes, medical diagnosis, archeometry, fission-fusion of Βαρύτητα nuclei, reactors, electricity production medical therapy, agriculture, industry Nuclear Industry, Medical Diagnostics and Therapy, Fusion (2025?) 28

29 Applications 3. Study of Fundamental Particles Accelerators 99% used in applications : Medicine: radioisotopes, X-rays, therapy with particles beams Materials Industry: integrated circuits, ions implantation, production of alloys Chemistry/Biology/Solid State: synchrotron radiation, high intensity beams Food Industry: food conservation and sterilization Agriculture/Oceanography: samples dating Superconductivity Industry: magnets, radiofrequency cavities, high speed trains, separation of minerals, carbon purification, accelerators, energy storage Medicine: MRI, diagnosis and therapy of tumors, NMR tomography 29

30 Applications Detectors Industry: Geiger counters, scintillators, steel and carbon industry, food industry, defence systems Medicine: radiation detection, proportional ionization chambers tomography Solar Energy: Cerenkov counters, mirrors, solar panels Industry/Biology: bubble chamber techniques for map reading, cells recognition, identification of defect materials Electronics new protocols (PXI, fastbus ), faster electronics, ADC s, TDC s, more precise measurements Computers/Networks faster and cheaper computers, larger memories, more efficient architectures, faster networks New applications under study usage of accelerators for energy production and simultaneous neutralization of radioactive waste 30

31 Summary Standard Model: cornerstone of 20 th century science great success, but still missing ingredients ( symmetry breaking sector Several unanswered questions (no gravity, dark matter,...) LHC/CMS designed to produce and search for the higgs, Designed also to explore all possible physics at TeV scale Studying all reactions of interest at higher energies LHC/CMS will definitely discover the higgs (if it is there) Possible signatures from supersymmetric particles Can also probe new and unexpected physics, even signs of extra dimensions Expectations: LHC will reformulate our understanding of nature at the most fundamental scale 31