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Kaushik De University of Texas at Arlington September 26, 2012.

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Presentation on theme: "Kaushik De University of Texas at Arlington September 26, 2012."— Presentation transcript:

1 Kaushik De University of Texas at Arlington September 26, 2012

2 Introduction to the LHC September 26, 2012Kaushik De2 The Large Hadron Collder (LHC) at CERN near Geneva

3 LHC Underground The worlds most powerful particle accelerator In a tunnel, 16.8 miles around, 330 feet underground Running spectacularly for the past two years © CERN

4 Motivation Why do we need the LHC? We have an excellent description of the physical world around us Called the Standard Model (SM) of Physics Consistent with experiments and observations of nature from the smallest to the largest scale But many unsolved questions about the Standard Model and beyond 4September 26, 2012Kaushik De

5 Unsolved Questions A small biased selection: How do particles get mass? Higgs? Maybe solved by ATLAS already! What is Dark Matter? Unification of fundamental forces? How does gravity fit in the SM? Are there extra dimensions? Fine tuning of Higgs mass? … September 26, 2012Kaushik De5

6 Methodology How will the LHC help in solving the fundamental mysteries of nature? The LHC is a particle accelerator. Protons are accelerated close to the speed of light -> aim for head-on collision! Collisions occur millions of times/second We need a massive camera to take pictures of these particle collisions. The ATLAS experiment is the camera 6September 26, 2012Kaushik De

7 Why is the LHC Important? The LHC is at the energy frontier – and will remain there for the next few decades 7 TeV 8 TeV … TeV center-of-mass proton-proton collision energy Exploration of unknown frontier Discovery through precision measurements The ATLAS perspective Unprecedented data = Rich program of physics 193 publications in arXiv, and growing September 26, 2012Kaushik De7

8 ATLAS Experiment 8September 26, 2012Kaushik De

9 ATLAS Detector September 26, 2012Kaushik De9 Unique device to record pp collisions at the LHC

10 Some ATLAS Facts ATLAS took ~15 years to build and commission The detector is 45 meters long, 25 meters high, 7000 ton weight ATLAS runs 24 hours when in operation We expect to collect and analyze data from ATLAS for the next years The scale of ATLAS is far beyond anything done before in basic physics research 10September 26, 2012Kaushik De

11 People in ATLAS September 26, 2012Kaushik De11 Over 3000 collaborators from 174 institutes in 38 countries

12 U.S. Institutions at the LHC 12September 26, 2012Kaushik De

13 Texas on LHC Baylor University: CMS Rice University: CMS Southern Methodist University: ATLAS Texas A&M University: CMS Texas Tech University: CMS University of Houston: ALICE University of Texas, Arlington: ATLAS, WLCG University of Texas, Austin: LHC University of Texas, Dallas: ATLAS 13September 26, 2012Kaushik De

14 UTA Involvement in ATLAS UTA contributed to ATLAS for ~17 years Build and operate the Intermediate Tile Calorimeter SouthWest Tier 2 Computing Center for ATLAS at UTA Many contributions in hardware, computing and physics 15 authors from UTA were on Higgs paper 14September 26, 2012Kaushik De

15 Building ATLAS at UTA September 26, 2012Kaushik De15

16 More Pictures from UTA September 26, 2012Kaushik De16

17 UTA in the ATLAS Pit September 26, 2012Kaushik De17

18 It can be Fun… September 26, 2012Kaushik De18

19 Testing in the pit September 26, Kaushik De

20 Other UTA Contributions PanDA Distributed computing software used by ATLAS Deployed at hundreds of computing centers Used by thousands of physicists Computing Operations Billions of events collected and analyzed from the LHC to extract physics results All physics results need massive data processing UTA involved from the beginning PAT, AFP, shift coordination and many more contributions by other UTA faculty 20September 26, 2012Kaushik De

21 21 PanDA Similar to cloud computing engine But developed 8 years ago, long before cloud computing became a buzzword Used by ATLAS world-wide Many other experiments interested now One of the most important U.S. computing contributions to ATLAS Cited as example of Big Data innovation Major new initiative announced by Obama in April PanDA received $1.7M DoE ASCR Big Data grant Major focus of research effort at UTA September 26, 2012Kaushik De

22 ATLAS Jobs/week September 26, 2012Kaushik De22

23 SouthWest SuperComputing Center UTA leads the SouthWest Tier 2 center for ATLAS Multi-million dollar NSF funded facility Contributing to hundreds of physics papers Helps physicists in the SouthWest region to quickly analyze ATLAS data September 26, 2012Kaushik De23

24 SWT2 in LHC September 26, 2012Kaushik De24

25 September 26, 2012Kaushik De25 ATLAS Status ATLAS is operating with data taking efficiency > 95% Almost 20 fb -1 delivered by the LHC Highest luminosity so far = 7.73·10 33 cm -2 s -1 Total Collisions = 1.29·10 15

26 Two Years of LHC Operations LHC performance has been phenomenal Good start to 7 TeV program in 2010: 45 pb-1 recorded Outstanding in : ATLAS recorded 5.25 fb-1 in 7 TeV 14 fb-1 so far in 8 TeV Perspective: In 2011, almost 1 million top pairs produced, over half billion W bosons produced September 26, 2012Kaushik De26

27 What will ATLAS Measure September 26, 2012Kaushik De27

28 28September 26, 2012Kaushik De

29 According to Bookies 29September 26, 2012Kaushik De

30 September 26, 2012Kaushik De30 Some Standard Model Processes

31 September 26, 2012Kaushik De31 Start with the Top Quark World's largest sample of top quarks produced Precision SM tests, while looking for new physics Summer results in top quark production and decay arXiv: Measurement of the t-channel single top-quark production cross section in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector arXiv: Measurement of the top quark pair cross section with ATLAS in pp collisions at sqrt(s) = 7 TeV using final states with an electron or a muon and a hadronically decaying tau lepton

32 September 26, 2012Kaushik De32 W Polarization in Top Decays arXiV Test of Wtb vertex 1.04 fb -1 of data analyzed No anomalous couplings

33 September 26, 2012Kaushik De33 Search for tb Resonances arXiV fb -1 of data analyzed No excess observed Benchmark limit on mass W' R >1.13 TeV at 95% CL

34 Single top summary September 26, 2012Kaushik De34

35 September 26, 2012Kaushik De35 Physics with Gauge Bosons Study of W/Z are important SM measurements used in precision fits, PDG results, MC tuning... Anomalous results could signal new physics Topics W/Z production and decays, associated particles Di-boson production – high rates at the LHC Summer result ArXiv: : - Measurement of tau polarization in W->taunu decays with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV

36 September 26, 2012Kaushik De36 W and Z Production arXiV fb -1 of data analyzed Limits on triple gauge couplings

37 September 26, 2012Kaushik De37 Why did P. Higgs Visit ATLAS Higgs is was the last unobserved particle in the SM Global EW fit: m H = GeV Above plot shows region not excluded by ATLAS at the beginning of the summer

38 Whats a Higgs Boson? © CERN 38September 26, 2012Kaushik De

39 How to Look for the Higgs The Higgs boson has variety of decays H -> H -> ZZ H->WW H->bb H-> Hunt requires many techniques WW (*) l l < ZZ (*) llll ZZ ll September 26, 2012Kaushik De

40 Limits from Various Channels September 26, 2012Kaushik De40

41 Have we Found the Higgs? arXiv: , Phys. Lett. B 716 (2012) 1-29Phys. Lett. B 716 (2012) 1-29 H->ZZ->4l, H->WW->emnn, H->gg modes Combining September 26, 2012Kaushik De41

42 The Evidence September 26, 2012Kaushik De signal of a new neutral boson with mass GeV More details in colloquium by Haleh Hadavand in January, 2013

43 Future of Higgs Higher precision measurements Next, verify all decay modes Most important, ZZ, WW is most challenging Measurement of Higgs couplings Couplings to gauge bosons important for EWSB WWH and ZZH processes Many other couplings – global fit strategy Look for deviations – search for new physics beyond the Standard Model September 26, 2012Kaushik De43

44 Dark Matter Astronomy tells us: The matter we know is 5% of the universe The rest is dark matter And dark energy 80 year old mystery Maybe we can make DM at the LHC? SLAC/Nicole Rager 44September 26, 2012Kaushik De

45 September 26, 2012Kaushik De45 Search for Supersymmetry Doubling of SM particles, and more Higgs states None seen yet Most searches assume R-parity is conserved LSP = dark matter candidate Expect missing Et from LSP

46 September 26, 2012Kaushik De46 Scalar Top Search arXiv NGMSB model 2.05 fb -1 analyzed 2 SFOS leptons, missing Et, b-tag Consistent with SM

47 September 26, 2012Kaushik De47 SUSY Trilepton + Missing Et arXiv: Chargino+NLSP cascade 2.06 fb -1 analyzed Consistent with bkground

48 SUSY Mass Limits September 26, 2012Kaushik De48

49 September 26, 2012Kaushik De49 Prognosis for SUSY MSSM SUSY models OK since low mass Higgs found mSUGRA models in trouble: Baer et al, arXiV ATLAS pushing sparticle mass limits near 1 TeV These searches require high missing Et from LSP Maybe R-parity not strictly conserved – MPV models Maybe large mass splitting for stops and sbottoms – NMSSM models, focus of recent ATLAS searches

50 Combined stop results September 26, 2012Kaushik De50

51 Other BSM Searches September 26, 2012Kaushik De51

52 Mystery - why is Gravity so Weak Electromagnetism is confined to our usual three dimensions of space Maybe Gravity sees other dimensions of space? As the force is spread out, it is weakened. 52September 26, 2012Kaushik De

53 September 26, 2012Kaushik De53 Black Hole Signature of LED arXiv: fb -1 : require 3 high PT objects, at least 1 lepton Consistent with SM bkground Also sets limit on string balls

54 Extra Dimensions or Dark Matter Recent result: arXiv Photon + missing Et LED (ADD), WIMP models 4.6 fb-1 & TeV Consistent with SM September 26, 2012Kaushik De54

55 September 26, 2012Kaushik De55 Conclusion Successful two years with ATLAS at the LHC Low mass SM Higgs hunt is almost over! Precision measurements of Standard Model going well – no surprises so far Search for new physics on many fronts


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