Tilman Plehn. Dresden, 4/2009

Transcription

1 New Physics at the Universität Heidelberg Dresden, 4/2009

2 Outline

3 The Large Hadron Collider: starting Summer 20XX

4 The Large Hadron Collider: starting Summer 20XX Einstein: beam energy to particle mass E = mc 2 smash 7 TeV protons onto 7 TeV protons produce anything that couples to quarks and gluons search for it in decay products repeat every 25 ns [energy unit GeV: proton mass] huge detectors, computers, analysis... experimental particle physics prejudice, fun and smart comments... theoretical particle physics

5 New Physics at the The Large Hadron Collider: starting Summer 20XX Einstein: beam energy to particle mass E = mc 2 smash 7 TeV protons onto 7 TeV protons [energy unit GeV: proton mass] produce anything that couples to quarks and gluons search for it in decay products repeat every 25 ns huge detectors, computers, analysis... experimental particle physics prejudice, fun and smart comments... theoretical particle physics life as an experimentalist life as a theorist

6 New Physics at the The Large Hadron Collider: starting Summer 20XX Einstein: beam energy to particle mass E = mc 2 smash 7 TeV protons onto 7 TeV protons [energy unit GeV: proton mass] produce anything that couples to quarks and gluons search for it in decay products repeat every 25 ns huge detectors, computers, analysis... experimental particle physics prejudice, fun and smart comments... theoretical particle physics life as an experimentalist life as a theorist

7 The Large Hadron Collider: starting Summer 20XX Einstein: beam energy to particle mass E = mc 2 smash 7 TeV protons onto 7 TeV protons produce anything that couples to quarks and gluons search for it in decay products repeat every 25 ns [energy unit GeV: proton mass] huge detectors, computers, analysis... experimental particle physics prejudice, fun and smart comments... theoretical particle physics Everything you always wanted to know... Atlas/CMS: measure anything flying around signal: everything new, exciting and rare background: yesterday s signal Standard Model: theory of background QCD: evil background theory trying to kill us N events = σ L [ cross section times luminosity ] trigger: soft jets not on tape jet: everything except for leptons/photons crucial: what is inside a jet [q, g, b, τ tagged?] discovery N S / p N B > 5 σ (nb) proton - (anti)proton cross sections σ tot Tevatron σ b σ jet (E jet T > s/20) σ W σ Z σ jet (E jet T > 100 GeV) σ t σ jet (E jet T > s/4) σ Higgs (M H = 150 GeV) σ Higgs (M H = 500 GeV) events/sec for L = cm -2 s s (TeV)

8 Standard Model effective theory A brief history of our Standard Model mess... Fermi 1934: theory of weak interactions [n pe νe] (2 2) transition amplitude A G F E 2 probability/unitarity violation pre-80s effective theory for E < 600 GeV Yukawa 1935: massive particle exchange four fermions unitary for E M: A g 2 E 2 /(E 2 M 2 ) unitarity violation in WW WW current effective theory for E < 1.2 TeV [ energy!!] W

9 Standard Model effective theory A brief history of our Standard Model mess... Fermi 1934: theory of weak interactions [n pe νe] (2 2) transition amplitude A G F E 2 probability/unitarity violation pre-80s effective theory for E < 600 GeV Yukawa 1935: massive particle exchange four fermions unitary for E M: A g 2 E 2 /(E 2 M 2 ) unitarity violation in WW WW current effective theory for E < 1.2 TeV [ energy!!] Higgs 1964: spontaneous symmetry breaking unitarity for massive W, Z unitarity for massive fermions fundamental scalar below TeV

10 Standard Model effective theory A brief history of our Standard Model mess... Fermi 1934: theory of weak interactions [n pe νe] (2 2) transition amplitude A G F E 2 probability/unitarity violation pre-80s effective theory for E < 600 GeV Yukawa 1935: massive particle exchange four fermions unitary for E M: A g 2 E 2 /(E 2 M 2 ) unitarity violation in WW WW current effective theory for E < 1.2 TeV [ energy!!] Higgs 1964: spontaneous symmetry breaking unitarity for massive W, Z unitarity for massive fermions fundamental scalar below TeV t Hooft & Veltman 1971: renormalizability beware of 1/M couplings gauge theories without cut-off truly fundamental theory 35 years later no sign of weakness...

11 Standard Model effective theory What is the Standard Model? gauge theory with local SU(3) SU(2) U(1) massless SU(3) and U(1) gauge bosons massive W, Z bosons [Higgs mechanism] Dirac fermions in doublets with masses = Yukawas generation mixing in quark and neutrino sector renormalizability L m 2 W WµW µ m f ψψ + ghψψ? + g M HWµνW µν fundamental theory: particle content, interactions, renormalizability

12 Standard Model effective theory What is the Standard Model? gauge theory with local SU(3) SU(2) U(1) massless SU(3) and U(1) gauge bosons massive W, Z bosons [Higgs mechanism] Dirac fermions in doublets with masses = Yukawas generation mixing in quark and neutrino sector renormalizability L m 2 W WµW µ m f ψψ + ghψψ? + g M HWµνW µν fundamental theory: particle content, interactions, renormalizability

13 Standard Model effective theory What is the Standard Model? gauge theory with local SU(3) SU(2) U(1) massless SU(3) and U(1) gauge bosons massive W, Z bosons [Higgs mechanism] Dirac fermions in doublets with masses = Yukawas generation mixing in quark and neutrino sector renormalizability L mw 2 WµW µ m f ψψ + ghψψ +? g HWµνW µν M fundamental theory: particle content, interactions, renormalizability And how complete experimentally? dark matter? [solid evidence for low scale new physics!?] quark mixing flavor physics? [new operators above 10 4 GeV?] neutrino masses and mixing? [see-saw at GeV?] matter antimatter asymmetry? [universe mostly matter?] gauge coupling unification real? gravity missing? [mostly negligible but definitely unrenormalizaby] physical cut-off unavoidable, size negotiable, renormalizability desirable who the hell cares???

14 Standard Model effective theory H H Theorists care!! t W Heisenberg: compute quantum corrections to Higgs mass... [ t E < 1]

15 Standard Model effective theory H H Theorists care!! t W Heisenberg: compute quantum corrections to Higgs mass......and watch the field theory desaster unfold m 2 H m2 H g2 3 (4π) 2 2 Λ 2 m 2 W h i m 2 H + 2m2 W + m2 Z 4m2 t + Higgs mass pulled to physical cut-off Λ [where Higgs at Λ is not a Higgs] hierarchy problem Higgs without stabilization incomplete

16 Standard Model effective theory H H Theorists care!! Heisenberg: compute quantum corrections to Higgs mass......and watch the field theory desaster unfold t W m 2 H m2 H g2 3 (4π) 2 2 Λ 2 m 2 W h i m 2 H + 2m2 W + m2 Z 4m2 t + Higgs mass pulled to physical cut-off Λ [where Higgs at Λ is not a Higgs] hierarchy problem Higgs without stabilization incomplete Starting from data which......indicates a light Higgs...indicates higher scale physics [e-w precision data] easy solution: counter term but gauge theories don t do tuning or new physics at TeV scale: supersymmetry extra dimensions little Higgs composite Higgs, TopColor YourFavoriteNewPhysics... typically cancellation by new particles or discussing away high scale beautiful concepts, but problematic in reality TeV scale models in baroque state [wish they were gone...]

17 Standard Model effective theory H H Theorists care!! t W Heisenberg: compute quantum corrections to Higgs mass......and watch the field theory desaster unfold m 2 H m2 H g2 3 (4π) 2 2 Λ 2 m 2 W h i m 2 H + 2m2 W + m2 Z 4m2 t + Higgs mass pulled to physical cut-off Λ [where Higgs at Λ is not a Higgs] hierarchy problem Higgs without stabilization incomplete Expectations from the find light Higgs? find new physics stabilizing Higgs mass? see dark matter candidate?

18 Example: TeV scale supersymmetry H H Supersymmetry t W partner for each Standard Model particle SUSY obviously broken by masses, mechanism unknown not an paradigm: maximally blind mediation [MSUGRA, CMSSM] scalars m 0 fermions m 1/2 tri-scalar A 0 Higgs sector sign(µ), tan β assume dark matter, stable lightest partner measure BSM spectrum with missing energy at

19 Example: TeV scale supersymmetry H H Supersymmetry t W partner for each Standard Model particle SUSY obviously broken by masses, mechanism unknown not an paradigm: maximally blind mediation [MSUGRA, CMSSM] scalars m 0 fermions m 1/2 tri-scalar A 0 Higgs sector sign(µ), tan β assume dark matter, stable lightest partner measure BSM spectrum with missing energy at searches: MSSM conjugate Higgs field not allowed give mass to t and b? five Higgs bosons SUSY Higgs alone interesting would be another talk... list of SUSY partners spin d.o.f. fermion f L, f R 1/2 1+1 sfermion fl, f R gluon Gµ 1 n-2 gluino g 1/2 2 Majorana gauge bosons γ, Z Higgs bosons h o, H o, A o 0 3 neutralinos χ o i 1/2 4 2 LSP gauge bosons W ± Higgs bosons H ± 0 2 charginos χ ± i 1/2 2 4

20 Supersymmetric signatures New physics at the (1) discovery signals for new physics (2) measurements spectrum, quantum numbers (3) parameters TeV scale Lagrangian, underlying theory approach independent of new physics model Special about, except bigger than Tevatron beyond inclusive searches [that was Tevatron] lots of strongly interacting particles cascade decays to DM candidate general theme: try to survive QCD rates not good in α s/(4π) 0.01 (collinear) jets everywhere good observables needed aim at underlying theory

21 Supersymmetric signatures New physics at the (1) discovery signals for new physics (2) measurements spectrum, quantum numbers (3) parameters TeV scale Lagrangian, underlying theory approach independent of new physics model Special about, except bigger than Tevatron beyond inclusive searches [that was Tevatron] lots of strongly interacting particles cascade decays to DM candidate general theme: try to survive QCD rates not good in α s/(4π) 0.01 (collinear) jets everywhere good observables needed aim at underlying theory

22 Supersymmetric signatures New physics at the (1) discovery signals for new physics (2) measurements spectrum, quantum numbers (3) parameters TeV scale Lagrangian, underlying theory approach independent of new physics model Special about, except bigger than Tevatron beyond inclusive searches [that was Tevatron] lots of strongly interacting particles cascade decays to DM candidate general theme: try to survive QCD rates not good in α s/(4π) 0.01 (collinear) jets everywhere good observables needed aim at underlying theory ! o + 2! 1 # # " t 1t " 1! 2o q! o 2 g Prospino2 (T Plehn) % tot [pb]: pp & g g, q q ", t 1t " 1,! o 2! + 1, # # ",! o 2 g,! o 2 q q q " g g $S = 14 TeV NLO LO m [GeV]

23 New physics measurements b b µ µ Spectra from cascade decays more than 10 7 squark gluino events thresholds & edges m 2 ij = E i E j p i p j cos θ ij g b ~ χ o 2 µ ~ o χ 1 m 2 χ 0 < m 2 0 m 2 µ µµ < 2 m µ m 2 µ m2 χ 0 1 m µ the longer decay chain the better new physics mass spectrum from cascade decays

24 New physics measurements b b µ µ Spectra from cascade decays more than 10 7 squark gluino events thresholds & edges m 2 ij = E i E j p i p j cos θ ij g b ~ χ o 2 µ ~ o χ 1 m 2 χ 0 < m 2 0 m 2 µ µµ < 2 m µ m 2 µ m2 χ 0 1 m µ the longer decay chain the better new physics mass spectrum from cascade decays

25 2 1 1 New Physics at the New physics measurements b b µ µ Spectra from cascade decays more than 10 7 squark gluino events thresholds & edges m 2 ij = E i E j p i p j cos θ ij g b ~ χ o 2 µ ~ o χ 1 m 2 χ 0 < m 2 0 m 2 µ µµ < 2 m µ m 2 µ m2 χ 0 1 m µ the longer decay chain the better new physics mass spectrum from cascade decays Cascade masses from kinematics all decay jets b quarks [otherwise dead by QCD] gluino mass to 1% what s more in m ij? m " 0! 1 m~ l R m " 0! 2 m~ - m 0 q " L! 1 - m! "0 l R m~ - m! "0 m! "0 b ~ 1 - m m g ~ m~ - m 0 b " 1! 1 m~ - m g " 0! 1 m~ q L m~ g m~ b Sparticle masses and mass differences [GeV]

26 New physics measurements When do I believe it s SUSY QCD? gluinos: strongly interacting Majorana fermions Majorana = its own antiparticle first jet in gluino decay: q or q final state leptons with charges 50% 50% gluino = like sign dileptons in SUSY like events g ũ! + µ + g ũ *! " µ "! 0

27 New physics measurements When do I believe it s SUSY QCD? gluinos: strongly interacting Majorana fermions Majorana = its own antiparticle first jet in gluino decay: q or q g ũ! + µ + g ũ *! "! 0 final state leptons with charges 50% 50% gluino = like sign dileptons in SUSY like events µ " All new physics is hypothesis testing b b µ µ loop hole: gluino is Majorana if it is a fermion assume gluino cascade observed straw-man model where gluino is a boson: universal extra dimensions g b ~ χ 2 o µ ~ o χ 1 [spectra degenerate ignore; cross section larger ignore] compare angular correlations L d%/d#$ bb [events/bin] SUSY UED:! (1) = 0, "/2 UED:! (1) = "/ L = 100 fb -1 SPS1a Mass Spectrum #$ bb [deg]

28 New physics measurements When do I believe it s SUSY QCD? gluinos: strongly interacting Majorana fermions Majorana = its own antiparticle first jet in gluino decay: q or q final state leptons with charges 50% 50% gluino = like sign dileptons in SUSY like events Asymmetries shorter sqark decay chain shape between endpoints: ˆm = m qµ/mqµ max dominant pp q g with q : q 2 : 1 production asymmetry with reduced errors A(m µj ) = σ(jµ+ ) σ(jµ ) σ(jµ + ) + σ(jµ ) kind of similar for gluino decay gluino = fermion with like-sign dileptons sin θ/2 q µ µ q ~! o 2 µ ~ o! 1

29 Weak boson fusion Illustrating useful jets: spin of LSP u W +! 0 1 d! + 1 Majorana LSP with like-sign charginos? hypotheses: like sign charginos (SUSY) like sign scalars (scalar dark matter) like sign vector bosons (little Higgs inspired) chargino decay/kinematics not used want to bet we can tell them apart just using the jets? u W +! + 1 d

30 Weak boson fusion Illustrating useful jets: spin of LSP u W +! 0 1 d! + 1 Majorana LSP with like-sign charginos? hypotheses: like sign charginos (SUSY) like sign scalars (scalar dark matter) like sign vector bosons (little Higgs inspired) chargino decay/kinematics not used want to bet we can tell them apart just using the jets? u W +! + 1 d

31 Weak boson fusion Like-sign scalars or fermions? charged Higgs in 2HDM H + H same as simple H 0 W radiated off quarks [Goldstone coupling to Higgs] 1 + (1 x)2 1 P T (x, p T ) 2x p 2 T (1 x)2 P L (x, p T ) x m 2 W p 4 T scalars with softer p T,j ) 1 1/! d!/dp T (jet "+" + WBF H+H+ W +W P T (jet ), GeV/c 1

32 Weak boson fusion Like-sign scalars or fermions? charged Higgs in 2HDM H + H same as simple H 0 W radiated off quarks [Goldstone coupling to Higgs] 1 + (1 x)2 1 P T (x, p T ) 2x scalars with softer p T,j p 2 T (1 x)2 P L (x, p T ) x m 2 W p 4 T Like-sign vectors or fermions? little Higgs inspired start with copy of SM, heavy W, Z, f Lorentz structure reflected in angle between jets vectors with peaked φ jj ) 2, jet 1 1/# d#/d"!(jet 0.9 $+$ + WBF 0.8 H+H W +W "!(jet, jet ) 1 2

33 Weak boson fusion Like-sign scalars or fermions? charged Higgs in 2HDM H + H same as simple H 0 W radiated off quarks [Goldstone coupling to Higgs] 1 + (1 x)2 1 P T (x, p T ) 2x scalars with softer p T,j p 2 T (1 x)2 P L (x, p T ) x m 2 W p 4 T Like-sign vectors or fermions? little Higgs inspired start with copy of SM, heavy W, Z, f Lorentz structure reflected in angle between jets vectors with peaked φ jj Or else... nightmare: strongly interacting WW ) 1 1/! d!/dp T (jet SM W+W+ W +W + (quark partners) W +W + (only W Z ) P T (jet ), GeV/c 1

34 Fundamental parameters From kinematics to weak scale parameters parameters: weak-scale Lagrangian measurements: better edges than masses, branching fractions, rates,... flavor, dark matter, electroweak constraints,... errors: general correlation, statistics & systematics & theory problem in grid: huge phase space, no local maximum? problem in fit: domain walls, no global maximum? problem in interpretation: bad observables, secondary maxima? Probability maps of new physics want probability of model being true p(m d) have exclusive likelihood map p(d m) over m Bayesian: p(m d) p(d m) p(m) with theorists bias p(m) [cosmology, BSM] frequentist: best fitting point max m p(d m) [flavor] getting rid of parameters: integration vs projection era: (1) compute high-dimensional map p(d m) (2) find and rank local best-fitting points (3) predict additional observables

35 Markov chains Define set of representative points in new physics space measure of representative : likely to agree with data [Markov chain] evaluate any function over chain (1) probability to agree with data (2) Higgs mass from LEP and DM relic density rates from LEP and DM relic density dark matter detection from LEP and/or dates of birth of people on shift... anything goes

36 Markov chains Define set of representative points in new physics space measure of representative : likely to agree with data [Markov chain] evaluate any function over chain (1) probability to agree with data (2) Higgs mass from LEP and DM relic density rates from LEP and DM relic density dark matter detection from LEP and/or dates of birth of people on shift... anything goes Bayesian probabilities vs profile likelihood Which is the most likely parameter point? How does dark matter annihilate/couple? m 0 (TeV) M 1/2 (TeV) L/L(max)

37 Fundamental parameters MSSM map for four neutralinos with (diagonal) mass parameters M 1, M 2, µ three of four mass-eigenstate neutralinos observed alternative solutions in parameter space µ e+0 1e M 1

38 Fundamental parameters MSSM map for four neutralinos with (diagonal) mass parameters M 1, M 2, µ three of four mass-eigenstate neutralinos observed alternative solutions in parameter space 6e e e /! 2 3e-07 1/! e e M 1 M 1 quality of fit not useful: all the same... µ < 0 µ > 0 M M µ tan β M M µl M µr A t ( ) A t (+) m A m t let s try to not miss too many particles...

39 Beyond the Why theorists involved? want to learn statistics know about theory errors know about link with other observations and models Beyond the remember: unknown sign(µ), believe based tan β from m h (1) maybe it s new physics: (g 2) µ tan β strongly correlated and promising (g 2) SPS1a tan β 10.0± ± M ± ± M ± ± M ± ± M µl 193.2± ± M q3l 481.4± ± M br 501.7± ± µ 350.5± ±

40 Beyond the Why theorists involved? want to learn statistics know about theory errors know about link with other observations and models Beyond the remember: unknown sign(µ), believe based tan β from m h (1) maybe it s new physics: (g 2) µ tan β strongly correlated and promising (g 2) SPS1a tan β 10.0± ± M ± ± M ± ± M ± ± M µl 193.2± ± M q3l 481.4± ± M br 501.7± ± µ 350.5± ±

41 Beyond the Why theorists involved? want to learn statistics know about theory errors know about link with other observations and models Beyond the remember: unknown sign(µ), believe based tan β from m h (1) maybe it s new physics: (g 2) µ tan β strongly correlated and promising (2) maybe we will see BR(B s µµ) tan 6 β stop-chargino sector missing prediction of f Bs missing

42 Beyond the Why theorists involved? want to learn statistics know about theory errors know about link with other observations and models Beyond the remember: unknown sign(µ), believe based tan β from m h (1) maybe it s new physics: (g 2) µ tan β strongly correlated and promising (2) maybe we will see BR(B s µµ) tan 6 β stop-chargino sector missing prediction of f Bs missing M 1 M 2 M 3 Renormalization group analysis SUSY breaking, unification, GUT? scale-invariant sum rules? 1/M i log(q)

43 Beyond the Why theorists involved? want to learn statistics know about theory errors know about link with other observations and models Beyond the remember: unknown sign(µ), believe based tan β from m h (1) maybe it s new physics: (g 2) µ tan β strongly correlated and promising (2) maybe we will see BR(B s µµ) tan 6 β stop-chargino sector missing prediction of f Bs missing Renormalization group analysis SUSY breaking, unification, GUT? scale-invariant sum rules? fundamental theory at all scales happy neighbors!

44 New physics at the Need for new physics there is physics beyond Standard Model Higgs and new physics the same question should find and study it Supersymmetry one well-studied example solves the hierarchy problem easily explains dark matter cascade decays rule to determine underlying model not only the biggest, but also the coolest machine!

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