Fourth Tropical Workshop on Particle Physics and Cosmology FLAVOUR PHYSICS AND PRECISION COSMOLOGY 9-13 June 2003, Cairns, Queensland, Australia CP Violation, Dark Matter and Extra Dimensions in the D-Zero experiment at the Tevatron ? Peter Ratoff Lancaster University

The Tevatron p-p collisions at  s = 1.96 TeV _

The DØ Detector in Run 2 + New Software (OO C++) + STT displaced track trigger, Summer’03

Tevatron operating parameters 396 – 132 ns 2 x cm -1 s TeV 6.5 – 11 fb Run ns 3.5  s Bunch spacing 4.5 x cm -2 s -1 2 x cm -2 s -1 Luminosity 1.96 TeV1.8 TeV c.m. energy ~200 pb  110 pb -1 Integrated Luminosity – 1996 Date NowRun 1

Run 2 Luminosity Performance

Physics in Run 2 W: mass, width, gauge couplings Top: mass, cross- section, branching ratios Electroweak Jet cross-section, shapes  multijet events QCD Higgs, SUSY, extra dimensions, leptoquarks compositeness, etc. Searches Lifetimes, cross-section, B c,  B, B s studies, CP violation, x s Heavy flavour # events in 1 fb

Detector Performance: electrons and muons Electrons: Muons D0: 10% Lumi error

Detector Performance: Jets Dominant systematic error: Jet energy scale (will improve with statistics)

Detector Performance: b’s and B’s Signed IP Jet TrackInteraction vertex Golden mode for CP viol’n (Sin2  )

Detector Performance: Taus Z   +  -  e  h Evidence for Z   +  -  e  h (similar study in Z  h ) Isolated electron opposite to narrow, single track jet. Signal enhanced using NN: (New at DØ)

Putting everything together: the top ! 3  observation X-section:

B Physics at the Tevatron? Large Cross Section! Produce bottom mesons with all flavor combinations as well as bottom baryons –B d, B u, B c, B s,  b,  b,... DØ is a multipurpose detector capable of reconstructing many B final states Rich B physics program –Cross-sections –B s mixing –B lifetime –CP violation in B d and B s –Rare decays bb BsBs BdBd

B Physics Triggers Have to go down from 2.5 MHz crossing rate to 50 Hz writing to disk (0.25 MB/event) –Sophisticated 3-level trigger system Most useful triggers for B physics so far: dimuon triggers (simple and unprescaled) –Central (|  | 3.5 GeV –Forward ( GeV But can also do physics with single muon trigger... Coming soon (this summer): –L2 track trigger (track match to  /e) –L2 (STT) silicon track trigger (displaced vertices)

T   +jet Begin with  in jet cross section Extract b content via fit to p T rel distribution Unfold jet energy resolution (unsmearing) Dominant error: jet energy scale corrections Inclusive b cross-section

J/  data sample Exploit J/    +  – mode Results based on 40 pb -1 collected data (75k J/  ) Calibration not finalized, mass not in good agreement with PDG

Charged B lifetime Full reconstruction (B ±  J/  K ± ): no hadronization or momentum uncertainties = 1.76  0.24(stat) ps (PDG :  0.018) c  B = L xy M B / p T B

Semi-leptonic B meson decay 2% of current Run II data ! single muon trigger works! abundance of SL B decays other decay channels to follow: B   D*X B   D+X B   D s X excellent opportunities for various B measurements (mixing, CP viol) good source of B hadrons for technical studies (trigger, b-tagging)

 : efficiency for a tag = D: Dilution = B mixing - flavour tagging status % % D= %D= %  = %  = % D= %D= %  = %  = % Jet tagMuon tag Signal region Sidebands  D 2 for signal Tagging power:  D 2 Significance of a mixing measurement is proportional to  D 2 Muon tag:Charge of highest p T muon in the event (excluding those from reconstructed B) gives (opposite-side) b-tag Jet tag: Q=  q i p Ti /  p Ti, count events with |Q|>0.2 Tagging performance measured in B+  J/  K+ - close to simulation expectations

CP violation in B hadron decays Able to reconstruct “golden’’ channels for CP violation measurements High statistics measurements with B S only possible at hadron colliders

B physics prospects (with 2fb-1)  B s mixing: B s  D s  (D s  ) ( x s up to 60, with x d meas. one side of U.T.)  Angle  : B 0  J/  K s (refine CDF Run1 meas. up to  (sin2  )  0.05)  CP violation, angle  : B 0   (  K), B s  KK(K  )  Angle  s and  s /  s : B s  J/   (probe for New Physics)  Precise Lifetimes, Masses, BR for all B-hadrons: B s, B c,  b … (CDF observed: B c  J/  e(  ). Now hadronic channels B c  B s X can be explored)  Cross sections  Stringent tests of SM … or evidence for new physics !! Both competitive and complementary to B -factories

SUSY models –SUSY is the best motivated scenario today for physics beyond the Standard Model doesn’t contradict precise Electroweak data predicts light Higgs unification of gauge couplings at GUT scale essential element of String Theories … provides explanation of Cold Dark Matter in the Universe! –SUSY must be broken symmetry (otherwise M SUSY = M SM ) variety of models proposed - differ mainly in the nature of the “messenger interactions” most experimental results obtained in the context of the SUGRA and GMSB models

SUSY production Neutralinos/charginos - trilepton channel - dilepton channel squarks/gluinos (dominant) –jets + mE T stop and sbottom b 1  b  2 0   1 0 e + e - ~ ~ ~ ~ squarks and gluinos are quite heavy  decay via multi-step cascades:  many high Pt jets and leptons plus large missing transverse energy

SUGRA models SUSY breaking is communicated to the physical sector by gravitational interactions GUT scale parameters + RGE’s  low-scale phenomenology M 0 = common scalar mass M 1/2 = common gaugino mass A 0 = common trilinear coupling value tan  ratio of the V.E.V. of the two Higgs doublets sign of  = Higgsino mass parameter  LSP is lightest neutralino - a neutral WIMP  excellent CDM candidate Highly constrained minimal SUGRA

GMSB models ‘Messenger’ sector couples to source of SUSY-breaking and physical sector of MSSM (through gauge interactions) The identity of the NLSP and its lifetime determine the phenomenology SMTCFTCAL Tracks as we knowKinksLarge dE/dx Hot cell Photons as we know Impact parameter slepton l  lG cc NLSP neutralino  G

Current DØ searches for new phenomena Model Independent e  + X Supersymmetry: SUGRA-inspired Jets + Missing E T (Squarks) Trileptons (Gauginos) GMSB Diphotons + Missing E T Leptoquarks 1 st and 2 nd generations New Gauge Bosons Dielectrons Large Extra Dimensions Dielectrons + Diphotons Dimuons

Jets + missing E T Generic signature for squarks and gluinos which, in SUGRA inspired models, cascade decay to (quarks and gluons  jets) + (two LSP’s  missing E T ) “Proof of existence” with ~ 4 pb -1 Select events with at least one jet with p T > 100 GeV Apply topological cuts (e.g., on jet- missing E T angles) Simulate physics backgrounds (with real missing E T ) Estimate the large instrumental QCD background from the data (empirical fit) No surprise: For missing E T > 100 GeV: 3 events observed vs. (2.7  1.8) expected

BackgroundsData GeV < M(ee) < 70 GeV p T (e 1 ) > 15 GeV, p T (e 2 ) > 10 GeV 3216± ± 19.1 M T > 15 GeV 96.4± 8.1 Add. Isolated Track, p T > 5 GeV 3.2± 2.3 Missing E T > 15 GeV 0.0± 2.0 eel + X Signal: Start from dielectron sample (~40 pb -1 ) Typical mSUGRA selection efficiency: 3 to 4% at the edge of the excluded region Sensitivity still about a factor 7 away from extending the excluded domain “Golden channel”: very low backgrounds, but large statistics will be needed allows for  h Similar analysis in the e  l channel

GMSB - diphotons In GMSB, the LSP is a light gravitino With a “bino” NLSP, the signature is therefore two photons with missing E T : Require two isolated photons with p T > 20 GeV Apply topological cuts Determine the instrumental QCD background from the data (inversion of photon quality cuts) Theory = "Snowmass“ slope: M = 2 , N 5 = 1, tan  = 15,  > 0 With ~50 pb-1, the Run I limit is approached

Large Extra Dimensions Search for the effects of KK graviton exchange in the ee,  and  final states: Two discriminating variables are used: the dilepton/diphoton mass the scattering angle in the rest frame where M s is the fundamental Planck scale. To solve the hierarchy problem, one can have M s in the TeV scale for n > 2 extra dimensions (n=1 is ruled out and n=2 is tightly constrained).

LED in the ee/  channels Require 2 EM objects with p T > 25 GeV and missing E T < 25 GeV Fit  G => M S > 1.12 TeV in GRW formalism Determine Physics backgrounds from simulation Instrumental backgrounds from data (with ~50 pb -1 : close to Run I, similar to LEP) M EM-EM = 394 GeV cos  * = 0.49

LED in the  channel M  = 347 GeV Require 2 opposite sign muons with p T > 15 GeV and M  > 40 GeV Determine Drell-Yan background from simulation QCD background from data With ~ 30 pb -1 : M S > 0.79 TeV in GRW formalism (New channel at the Tevatron, similar to LEP)

Fit the distributions in the M ll - cos  * plane to determine the value of  G (  G = 0 in SM) Di-EM analysis:  G = 0.0  0.27 TeV -4 Di-Muon analysis:  G = 0.02  1.35 TeV -4 Extract 95% CL upper limits on  G Translate to 95% CL lower limits on Planck scale M S, in TeV, using different formalisms for F Large Extra Dimensions Search: Results Di-EM limit close to Run I Di-Muon (new )

Summary and Conclusions DØ is almost fully operational following major upgrades for Run II (some trigger improvements to come e.g STT) The Run I data sample has now been exceeded and physics results are emerging from the first pb-1 The B physics potential of DØ has been established Good lepton, photon, jet and missing E T detection enables DØ to perform many new physics searches Measurements of cosmological significance can be expected in the coming few years with data samples > 5 fb-1 CP violation (unitary triangle angles, beyond the SM?) dark matter candidates/limits (e.g. neutralino LSP) large extra dimensions/limits

SUSY Particle Zoo

Where we are standing: Run I vs Run II Run IIRun I (120 pb -1 ) SUSY search  x BR  < 2.2 pb (42 pb -1 ) M(  0 )=62 GeV mE T >15 GeV  x BR  < 0.3 pb M(  0 )  60 GeV mE T >10-15 GeV lll +mE T (Run I) eel +mE T (Run II) A x   <0.1 pb (33 pb -1 ) mE T >45 GeV ? e  +mE T  x  < 4.2 pb (4.1 pb -1 ) mE T >70 GeV Jets +mE T (new)

Where we are standing: Run I vs Run II M LQ > 179 (43 pb -1 )M LQ > 225 GeV1 st LQ 2 e + 2 jets Run IIRun I (120 pb -1 ) Analysis M S > 1.0 (50 pb -1 )M S > 1.1 TeVLED 2em M(  0 ) > 66 (40 pb -1 )M(  0 ) > 75 GeV SUSY 2  + mE T M LQ > 157 (30 pb -1 )M LQ > 200 GeV 2 nd LQ 2  + 2 jets M S > 0.71 (30 pb -1 ) LED 2  (new) A lot of another analyses are going on: gauge interactions search, SUGRA particles search with the different jets & leptons & mE T signatures … etc