The Particle Physics Playbook Konstantin Matchev

This talk will not contain Predictions of what new physics CDF might discover The latest new physics models –See talks from LHC conference at Santa Barbara The latest advances in NLO calculations –See talks from LHC conference at Santa Barbara –Come to F. Petriello’s talk on Wednesday morning The model I have recently been working on –But in case you are interested: UMSSM = NMSSM + U(1) +  + exotica Interesting features of UMSSM –Z’ gauge boson and Z’-ino neutralino –Scalar LSP: right-handed sneutrino dark matter –TeV scale colored exotics –Z 3 discrete symmetries B 3 (leptophobic Z’), L 3, M 3 –R-parity violation –Stable proton Lee,KM,Nasri 2007 Lee,KM,Wang 2007 Luhn,Lee,KM 2007 Kang,Langacker,Nelson 2007

This talk will contain Jokes Homework assignments General classification of new physics signatures –Bump hunting –Bean counting Review of (some) existing techniques for precision measurements at hadron colliders –Mass measurements –Spin measurements Opportunities to do such measurements with existing Tevatron data The discussion will be signature-based and largely model-independent Useful “theorems”

What do we do for a living? Look for new particles. How? -Full reconstruction (bump hunting) -Backgrounds can be measured from data -Easy to do mass, width measurements -More likely to be done with early data -Excess of events (bean counting) -Prone to systematic errors -Difficult to measure particle properties -Less likely to be done with early data It is worth thinking about bump hunts first! It is possible to give an exhaustive and systematic classification of all resonance searches Run II V. Shary CALOR04

Classification of resonance searches How many resonances per event? (1 or 2) How many objects does the resonance decay to? (2,3,4,…) What are those objects? Note the absence of a “Missing energy calorimeter”

List of all di-object resonances The scheme can be generalized to –three body decays etc. –pair-production etc.  e  jetb   Z’LQ W’ eZ’LQ W’  h jetZ’LQ bh  hW’ - ‘Z’, ‘t’, ‘W’…

A single resonance decaying to 3 objects (inclusive) Pair production of resonances Such searches are very model-independent To summarize - just ask: –How many new resonances are present in each event? –What did each one decay to? More complicated topologies

Homework (Warm-up exercise) Classify all existing CDF new physics (and Higgs) searches according to this scheme. Notice if there are any remaining empty slots. Can you think of any reason why such a resonance should not exist? –If “yes”, report to me and/or the Theory Group –If “no”, then proceed to next step. Think of a model where such a resonance would exist. (Ask your theory friends for help.) Is there a good reason why CDF is not looking for such a resonance? –If “Yes”, go back to previous step. –If “No”, proceed. Is D0 looking for it? If yes, talk to D0. If no, proceed. Are ATLAS/CMS going to look for it? If yes, talk to them. If no, proceed. If you got here, talk to your physics coordinator.

Useful Theorems Hinchliffe’s theorem: If the title of a paper is in the form of a “Yes/No” question, the answer is always “No” –Corollary: “If the abstract of the paper claims the answer is “Yes”, the paper is wrong and should be rejected” Folk theorem: If you ask a theorist a question starting with “Is it possible to have a model where [I get signature X]?” the answer is always “Yes” –Exception: Signature X violates some fundamental conservation law (e.g. charge conservation, Lorentz invariance etc.) –Corollary: CDF should be on the lookout for all allowed signatures. Some “easy” examples –e  resonance –trilepton resonance

SUSY and R-parity Violation What is R-parity? –SM particles: +1 –Superpartners: -1 Who needs R-parity? –Proton decay –Dark matter What if R-parity was violated? –Superpartners will still decay down to the LSP –The LSP will decay to SM particles (resonance?) –The LSP does not have to be neutral(ino)!

R-parity Violation Baryon number violation: W BV = ijk U i D [j D k] Lepton number violation: W LV = ijk L i Q j D k + ijk L [i L j] E k

Signatures of R-parity Violation 2 LSP’s per event, large cross-sections The leptons may be different flavor LSPUDDLQDLLE 00 3j ljj, jjll gluino3j ljj, jjjjll squark2jlj jll sleptonljjj2j l sneutrino jj 2jll chargino*3j ljj, jj 3l

Midpoint summary Look for all possible resonances R-parity violation: SUSY under the lamppost –Large rates from squark/gluino production –Resonances from LSP decays –Hard leptons if LV LQD, LLE

Missing energy signatures Motivated by the dark matter argument Inevitable model dependence No resonances Follow the general classification: –How long was the cascade? –What were the emitted SM particles? What can we measure? Mass? Spin?

Missing energy signatures  e  jetb   WWW  e  jet bttt  A B a C b a b Can be extended to longer cascades Two such cascades per event Repeat the previous homework Can we measure the mass/spin of A,B?

Mass measurements Single semi-invisibly decaying particle Use the transverse mass distribution W e

Mass measurements A pair of semi-invisibly decaying particles Use the “stransverse” mass (M T2 ) W e W  Kong, KM This formula is valid for m =0. Lester,Summers 99 Barr,Lester,Stephens 03

Homework Use M T2 to measure the W mass in dilepton W pair events Use M T2 to measure the top quark mass in dilepton tt-bar events Cho,Choi,Kim,Park 2008

SUSY or UED? Folk theorem: Any signals of new physics can be explained with some SUSY model A more recent theorem Any SUSY signature can be faked by some UED or Little Higgs model –Corollary: Any signal of new physics can have alternative explanations unless we can measure spins KK masses at one-loop Cheng,KM,Schmaltz 2002 Only the LKP is stable. The LKP is neutral (DM!)

Model discrimination/Spin determination What is the nature of A,B,C,D? –Find $N,000,000,000 and build an ILC –Find the momentum of A, fully reconstruct the event –Study m 2 distributions of visible particles The distributions depend on –Spins of A,B,C,D –Masses of A,B,C,D –Chirality of couplings –Initial state (particles vs antiparticles) Most spin studies compare two sets of spin assignments, but fix everything else That is not a true measurement of the spin Battaglia,Datta, DeRoeck,Kong,KM 05 Cheng,Engelhardt, Gunion,Han,McElrath 08 Athanasiou et al 06, Kilic,Wang,Yavin 07, Csaki,Heinonen,Perelstein 07, S. Thomas (KITP)

“SUSY” vs “UED” Mass spectrum {A,B,C,D}={1000,600,420,210} GeV Burns,Kong,KM,Park 08

Homework Consider dilepton WW events and try to discriminate the following alternatives: –W pair -> 2 leptons + 2 neutrinos, –Slepton pair -> 2 leptons + 2 neutralinos –Chargino pair -> 2 leptons + 2 sneutrinos –KK lepton pair -> 2 leptons + 2 KK photons Consider dilepton top pair events and try to discriminate the following alternatives –t -> b W -> b+lepton+neutrino –t -> b H + -> b+lepton+neutrino –stop -> b chargino -> b+lepton+sneutrino –KK top -> b KK W -> b+lepton+KK neutrino

A positive note Clean multilepton + MET events in SUSY –3 leptons: gold plated mode –4 leptons: platinum plated? –8 leptons: ??? What is the max number of leptons? hino qLqL lLlL lRlR wino bino qL q wino l bino l lLlL hino ll lRlR

Advertisement Check out the MC4BSM workshops –Fermilab 2006 –Princeton 2007 –CERN 2008

Summary Think about model-independent signature based searches. –Resonances –Missing energy Ask for the theory model later. Think of ways to test the proposed methods for precision measurements at the LHC (masses, spins etc.) with existing Tevatron data. Do the homework.

BACKUP SLIDES

How do we know LHC will find anything new or interesting? The X 7 argumentWhere is the Higgs?