A paradigm shift in physics until 2025 because of the LHC? David Côté (CERN)

Transcription

1 A paradigm shift in physics until 2025 because of the LHC? David Côté (CERN)

2 Overview Brief self-presentation Introduction Physics beyond the Standard Model The Large Hadron Collider (LHC) My research plans Search for dark matter produced in the laboratory Development of diamond-based detectors 2

3 Before my thesis (2002): B Ph.D. BaBar 0 4 B After my thesis (2007): B V stat syst theo 0 B stat 0.08syst 0.01theo ub stat syst theo 10 4 Phys.Rev.Lett. 98, (2007) Eur.Phys.J. C38, (2004) 3

4 Postdoc positions on ATLAS CERN Research Fellow, Marie Curie Fellow DESY Fellow ( ) Main work: Inclusive searches for supersymmetry (SUSY) coordinating a team of 30 people Editorial Board for Higgs analysis Software infrastructure development data reconstruction coordinator at Tier0, derived physics datasets, SUSY group production, etc. 4

5 Introduction 5

6 Large Small Large and small scale physics related by the Big Bang and by dark matter! 6

7 The Standard Model Interactions of elementary particles (quarks & leptons) via three forces (electro-magnetic, strong, weak). Missing link: the Higgs boson All the predictions of the Standard Model agree with experimental data since

8 Problems of the Standard Model Incomplete, does not include: gravity dark matter dark energy neutrino masses Theoretical inconsistencies at very high energy Fine-tuning: hierarchy problem of Higgs mass (~10-32 ) absence of anti-matter in the Universe (~10-9 ) 8

9 Hypotheses beyond the Standard Model New particles Supersymmetry (SUSY) New symmetry New force New spatial dimensions Number of articles on ArXiv per topic and year 9

10 About SUSY Boson fermion symmetry Main motivations: solves fine-tuning problem of Higgs mass neutralino is WIMP dark matter candidate Drawback: minimal SUSY model has 124 free parameters! a few parameters are decisive: stop mass, gluino mass 10

11 The LHC at CERN Collides protons and heavy ions Circumference: 27 km Large experiments: ATLAS, CMS, LHCb, Alice Energy ( ): 7 TeV (max: 14 TeV) Luminosity (2011): 3.6 x cm -2 s -1 (max: 50 x cm -2 s -1 ) LHCb ATLAS ALICE CMS 11

12 The ATLAS detector ATLAS-Canada: 9 universities + TRIUMF Hermetic detector in concentric layers. 12

13 Detection of particles ATLAS can measure all the known particles neutrinos & dark matter measured from missing momentum (energy conservation) E T miss 13

14 Status of data-taking Proton collisions in energy: 7 TeV integrated luminosity: 2010: ~0.035 fb : ~5 fb -1 Proton collisions in 2012 LHC start-up is ongoing target luminosity: fb -1 energy: 8 TeV 2x sensitivity for high-mass searches 14

15 Tremendous success! LHC performance beyond expectation 350 papers published in expanded our knowledge of particle physics in almost all domains: beyond Standard Model Higgs boson b and top quarks strong interaction (QCD) electroweak interaction quarks & gluon plasma 15

16 Highlighted results First LHC discovery! new bb bound-state: b (3P) arxiv: accepted by Phys.Rev.Lett. Updated flagship searches Higgs SUSY 16

17 Higgs: CERN Seminar (Dec. 2011) Press event to present updated Higgs results by ATLAS & CMS 70 journalists and 40 media on site circulation to 629 million people Webcast: distinct viewers Twitter: followers Live blog: followers 17

18 Great work by CERN for science popularization International exposure for the LHC 18

19 ATLAS-CONF Higgs: exclusion (Moriond 2012) Full mass range Zoom at low mass range Standard Model Higgs excluded for all relevant masses except for two narrow regions! LEP excess at 114 GeV now excluded by ATLAS at 95% C.L. 19

20 ATLAS-CONF Higgs: excess (Moriond 2012) Higgs mass Dominant decay channel Local p 0 Global p 0 ATLAS 126 GeV H, H ZZ CMS 125 GeV H CDF GeV H bb D GeV H WW

21 Is it really the Higgs? Most significant raw data shown on this slide (H ) size of excess should not be overstated need more data to conclude 4x more data in 2012 discovery or full exclusion is almost guaranteed! 21

22 Consequences of m H =125 GeV If confirmed, a Higgs boson of ~125 GeV would be really great! 5 measurable channels at the LHC lots of information, precise tests Compatible with broad hypotheses beyond Standard Model constraints on many specific models Finding the Higgs would be a great success, but it is only a milestone towards the ultimate goal of discovering physics beyond the Standard Model at the LHC. 22

23 My research work Search for dark matter produced in the laboratory past, present, future Development of diamond-based detectors 23

24 How to create a paradigm shift in physics? Dark Matter experimental evidence already established dominant component of the Universe here & now 24

25 Dark matter in the laboratory Production: E=mc 2 jet WIMP jet With sufficient energy, it is plausible that we produce dark matter at the LHC. Detection: If so, dark matter should be detectable with the ATLAS detector after careful data analysis. E T miss 25

26 The dark matter search triangle astrophysical dark matter q q WIMP WIMP direct weak production WIMP = 0 LHC indirect strong production SUSY q g q ~ 0 q g q ~ 0 26

27 Astrophysical properties of dark matter Detected by gravitational effect galactic rotation curves, gravitational lensing composes 22% of the present Universe Favored explanation: Weakly Interacting Massive Particle (WIMP) direct searches by dedicated experiments CDMS, CoGeNT, COUPP, CRESST, DAMA, DEAP/CLEAN, PICASSO, SIMPLE, XENON, 27

28 The dark matter search triangle astrophysical dark matter q q WIMP WIMP direct weak production WIMP = 0 LHC indirect strong production SUSY q g q ~ 0 q g q ~ 0 28

29 direct dark matter searches The same process is studied by astro-particle and the LHC interpreted with effective contact interaction operators the LHC powerfully complements direct detection experiments! probes unexplored region at very low WIMP mass better spin-dependent sensitivity than direct detection 29

30 The dark matter search triangle astrophysical dark matter q q WIMP WIMP direct weak production WIMP = 0 LHC indirect strong production SUSY q g q ~ 0 q g q ~ 0 30

31 Search for strong SUSY production First ATLAS-SUSY paper Phys. Rev. Lett. 106, (2011) l + E T miss heavy colored particles production fully benefits from the LHC power if SUSY: gluinos & squarks surpassed Tevatron with only fb -1 most cited papers of the LHC so far 31

32 Dark matter interpretation ATLAS: E T miss +jets+lep LHC & astro-particle both constrain msugra 32

33 The E T miss +jets+lepton search A flagship analysis of the LHC discovery channel for: new heavy colored particle (SUSY or other) dark matter (WIMP) My personal contributions analysis coordinator since September 2011 brand new result released on March 17 th! look for different experimental signatures new signal samples with very low lepton p T simultaneous measurement of signal and main backgrounds from fit to multiple data samples large increase in sensitivity interpretation of results with simplified models l + E T miss 33

34 ATLAS-CONF Inputs to simultaneous fit Jet multiplicity in control samples constrain background uncertainties Effective mass shape increases signal exclusion sensitivity 34

35 ATLAS-CONF New results (March 2012) Huge improvements since September! Most advanced SUSY search in the world! 35

36 ATLAS-CONF New results (March 2012) l + E T miss First LHC search for SUSY with soft lepton Sensitivity to compressed SUSY increased by 25x 36

37 The future of SUSY searches Wished-for easy SUSY is not there nice challenge for the talented researchers! 5 fb -1 = billion collisions* luminosity: fb -1 energy: TeV And if there is no SUSY? dark matter exists nevertheless! excess of E T miss over the known background independent of any model about new physics *2 billion collisions recorded. 37

38 LHC timeline First collisions TeV Energy: 8 TeV Lumi: fb -1 Energy: 14 TeV Lumi: 50 fb -1 Energy: 14 TeV Lumi: 300 fb -1 Energy: 14 TeV Lumi: 3000 fb First LHC beams. Energy: 7 TeV Lumi: fb -1 Phase-I upgrade LHC: luminosity ATLAS: trigger, muons Phase-0 upgrade LHC: energy ATLAS: inner-most pixels Phase-II upgrade LHC: luminosity ATLAS: tracker, FCAL 38

39 ATLAS upgrade Phase-II (2022) Tracker and Forward Calorimeter damaged and saturated at this extremely high luminosity. Tracker: entirely new detector with new design very exciting opportunity! Calorimeter: modest modifications to existing design natural continuity of past ATLAS-Canada contributions 39

40 New tracker Current ATLAS tracker All solid-state Outside inside: silicon strips planar silicon pixels inner-most layers need R&D: high-voltage silicon pixels? 3D silicon pixels? diamond pixels? new tracker 40

41 Diamond-based detectors 41

42 Diamond technology: a good strategy for ATLAS-Canada Diamond-based detectors are established for beam monitoring in ATLAS large potential for calorimetry & tracking Build upon existing Canadian leadership in this community More upgrade projects are also very interesting even if not covered in this talk! 42

43 Pros & cons of diamond Cons: high cost, large-scale production uncertainties small operational experience Pros: no leakage current (i.e. small background) signal to noise largely insensitive to temperature high thermal conductivity radiation hard fast response compared to silicon Diamond should produce better overall performance if practical problems are solved and tracker design is correctly optimized. 43

44 Topics of diamond R&D Optimize tracker layout to take advantage of good properties of diamond e.g. reduce dead material from cooling Optimize front-end electronics for S/B and fast response of diamond Optimize diamond quality for operations after large irradiation doses Learn how to produce diamond ourselves potentially reduce the production cost 44

45 Conclusion The LHC and ATLAS perform beautifully and have extraordinary scientific potential the Higgs boson is just the beginning Producing dark matter in the laboratory would create a paradigm shift in physics The development of diamond-based detectors could lead to major Canadian contributions to the ATLAS upgrades 45

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47 Details of Higgs exclusion Moriond EW

48 Higgs combination Moriond EW

49 Higgs p-values Moriond EW

50 Higgs best fit Moriond EW

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52 Forward Calorimeter upgrade Two options considered: MiniFCal or sfcal MiniFCal: additional instrumented shielding for FCAL copper absorber, diamond sensors ATLAS-Canada leadership in this project 52

53 Searches for Supersymmetry 53

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55 The interpretation of LHC data has some model-dependence (JHEP 1012:048(2010), arxiv: ) 55

56 Direct detection of dark matter V. Zacek, LLWI 2007 D. Cline WIMP WIMP quark quark 56

57 NEUTRALINO INTERACTION CROSS SECTIONS Z q ~ q q q q q q H Spin-dependent Spin-independent General form of cross sections: A 4G 2 F M M M A M A 2 C A F( q 2 Enhancement factor ) C A SI : Spin independent coherent interaction A 2 C A SD : Spin dependent interaction <S p,n > 2 F(q 2 ) : nucl. form facor important for large q 2 and large A

58 After the LHC e+e- colliders: ILC (250 GeV 1 TeV) CLIC (1 3 TeV) 58

59 arxiv:

60 Simplified models 60

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62 collisions of quarks/gluons E = [ ] TeV for 7 TeV arxiv:

63 arxiv: accepted by Phys.Rev.Lett. 63

64 Higgs mass fine-tuning in SUSY 64

65 Towards the Planck energy 65