LC Physics in LHC Era

Transcription

1 LC Physics in LHC Era Frank E. Paige, BNL LHC scheduled to start in 27. LC will not be before 212 [TESLA TDR]. LC technology still needs further R&D [Loew]. Must justify LC physics assuming LHC has been operating for 5y. Focus of worldwide LHC/LC Study Group [Weiglein,... ]: georg/lhclc/ schellma/lhclc/ Goal is to justify general expectation that LHC will find new physics, but LC needed for full understanding. Concurrent running of LC with LHC is essential. Will concentrate on Higgs and SUSY physics. Frank E. Paige 1 LC Physics in LHC Era

2 Higgs Physics Electroweak precision data from SLD/LEP/Tevatron test Standard Model (SM) to 1% [LEPEWWG-22]: Preliminary A,l fb.2399 ±.53 A l (P τ ) ±.41 A l (SLD).2398 ±.26 A,b fb ±.31 A,c fb.2322 ±.79 <Q fb >.2324 ±.12 χ theory uncertainty α had = α (5).2761± ±.12 Average ± χ 2 /d.o.f.: 1.6 / 5 2 m H [GeV] α (5) had =.2761 ±.36 m Z = ±.21 GeV m t = ± 5.1 GeV sin 2 θ lept eff = (1 g Vl /g Al )/4 Excluded Preliminary m H [GeV] Standard Model Higgs has M h 2GeV accessible at 5GeV LC. Frank E. Paige 2 LC Physics in LHC Era

3 Caveats: SM fit not very good; conflict with direct bounds worsens if A b fb and A removed. [Chanowitz]. SLC Higgs bound is weakened to 4GeV if new physics adds additional T [Chivukula]. Agreement with SM is then accidental. Must still avoid FCNC, etc. T GeV m H 95% CL 68% CL 1 GeV 15 GeV 2 GeV Τ 3 GeV 5 GeV 7 GeV 1 GeV S Should expect light Higgs both in SM and in SUSY. Best physics case for LC-5: can access both e e Zhand e e ννh. Frank E. Paige 3 LC Physics in LHC Era

4 Production of Higgs at LHC dominated by gg fusion. Cross section now known to NNLO [Harlander, Kilgore]. Dominant h h h γγ, bbmode swamped by QCD. Must rely on rare decays: ZZ 4. Key goal of ATLAS, CMS. h γγ has large γγ, γ j, and j j backgrounds. Needs outstanding EM resolution and 14 rejection for γ j. Detailed simulations OK, especially for M h 115GeV [CMS]. Events/5 MeV for 1 fb a) m γγ (GeV) Events/5 MeV for 1 fb b) m γγ (GeV) Probably the most carefully studied process at LHC. Frank E. Paige 4 LC Physics in LHC Era

5 h ZZhas much better S good resolution in both e and µ channels. B. ATLAS and CMS have Branching ratio becomes small when h WW is allowed. Rates are small [CMS]. Events / 2 GeV / 1 fb H ZZ* l + l l + l - tt + Zbb + ZZ* M l + l l + l (GeV) Various other channels may also be used.... Frank E. Paige 5 LC Physics in LHC Era

6 Signal significance LHC should discover Higgs for any mass above LEP limit. High luminosity allows observation in several channels at each mass, each with 5σ [ATLAS]. 1 2 H γ γ + WH, tth (H γ γ ) tth (H bb) H ZZ (*) 4 l H WW (*) lνlν WH WWW (*) H ZZ llνν H WW lνjj Total significance ATLAS 1 Similar results hold for SUSY Higgs in decoupling limit, M A MZ. L dt = 1 fb -1 (no K-factors) 5 σ m H (GeV) Mass resolution in γγ and (from Z) is 1%. Expect Mh Mh channels is 1%. 1%, and calibration Frank E. Paige 6 LC Physics in LHC Era

7 New work has emphasized WW fusion [Zeppenfeld... ]. Potential discovery channels, and important for measuring properties of Higgs. q q qq H W,Z W,Z q H q Complex analysis. Requires full simulation to study forward jet tags and central jet veto. Many backgrounds must be considered.... H WWanalysis uses double forward jet tag and central jet veto, angular correlation of from spin- Higgs. See excess in transverse mass σ acc (fb) M T E / ET 2 p /p T 2.1 Accepted dilepton σ 3 3fb 1 7fb m T (GeV) Frank E. Paige 7 LC Physics in LHC Era

8 evts / 5 GeV H ττ analysis uses double forward jet tag and central jet veto. Separate analyses for eµ, eeµµ, and h modes m H =12 GeV Z jj t t, WW EW Reconstruct M ττ by projecting /p T 3 on τ directions. 2 Accepted σ 1 fb 5fb m ττ (GeV) Want to use various Higgs processes to determine combinations of couplings. Inclusive cross sections known to NLO or NNLO. Must understand acceptance to same accuracy. Frank E. Paige 8 LC Physics in LHC Era

9 h Can ultimately measure WW Bσ Bσ (σ*br)/(σ*br) 1 2% [ATLAS]: WW ττ and other processes with * H WW l ν l ν * H ZZ 4 l H γγ * VBF: H WW l ν VBF: H ττ ATLAS + CMS -1 L dt=3 fb per experiment l ν (GeV) m H Expect comparable errors for some couplings that signal is a Higgs boson. reasonable confidence Frank E. Paige 9 LC Physics in LHC Era

10 Many more channels possible for MSSM Higgs at LHC. Plot assumes maximal stop mixing and no SUSY decays [ATLAS]: Frank E. Paige 1 LC Physics in LHC Era

11 5fb, compared to e e ZH at LC-5 has σ 3fb for e e qq [Snowmass1]: Premium on very high luminosity: 5fb 1 17 Z s at LEP. 25k events. Compare with Frank E. Paige 11 LC Physics in LHC Era

12 Can observe Higgs in missing mass independent of decay mode [Snowmass1]: NLC at 35 GeV (µ + µ - X) NLC at 5 GeV (µ + µ - X) Events/2.(GeV) (a) 115 GeV 12 GeV 14 GeV 16 GeV WW ZZ Events/2.(GeV) (b) 115 GeV 12 GeV 14 GeV 16 GeV WW ZZ Z Recoil Mass (GeV) Z Recoil Mass (GeV) Can observe all decay modes even invisible ones. Basis for detailed study of Higgs properties. Frank E. Paige 12 LC Physics in LHC Era

13 Analysis using TESLA detector and DELPHI algorithms can tag both bb and cc. Errors for 5fb 1 at 35GeV [Battaglia]: SM Higgs Branching Ratio m H (GeV/c 2 ) Theory errors (bands) dominated by quark masses; should improve.... Should also study measurements using e e ννhat 8GeV. Frank E. Paige 13 LC Physics in LHC Era

14 Clearly better than LHC: smaller errors with less theory uncertainty. Good enough to be interesting? In MSSM light Higgs has g hzz g SM hzz sin β α g hbb g SM hbb sinα cosβ Decouples for M A, but above errors still sensitive to: tan β 5 TESLA L = 5 fb -1 8GeV (68%) 45 6GeV (9%) GeV (95%) 3 Heavy Higgs not easy to detect at LHC. Simple SUSY models favor large M A, but these are useful limits m A (GeV/c 2 ) Frank E. Paige 14 LC Physics in LHC Era

15 Another example: Higgs-radion mixing [Hewett]: Mixing can have large effects on h ggbranching ratio as functions of unknown mixing parameter ξ. O Might observe deviation at LHC, but it would be difficult to separate from other effects. 1 Want to verify Higgs self-coupling by measuring Zhh: Small cross section; 8 events for 2fb 1 : Frank E. Paige 15 LC Physics in LHC Era

16 .6.4 κ=1.5 κ=1 SM: e + e - ZHH M H = 11 GeV σ pol [fb].2 κ= s[gev] Also want to measure e e tth. NLO result known [Dawson... ]. Really need 8GeV to have enough rate for this: 1 1 LO NLO σ(fb) 1 s=1 TeV s=5 GeV M h (GeV) Frank E. Paige 16 LC Physics in LHC Era

17 Supersymmetry SUSY at TeV scale is probably best motivated extension of SM.... SUSY production at LHC dominated by g and q. Cross section comparable to QCD at same Q 2. Cascade decays give multiple jets, leptons,..., plus missing χ 1 / E T. After simple multijet and /E T cuts cross section at large M eff /E T p T j is dominated by SUSY with S j B Events/5 GeV/1 fb Background for SUSY is SUSY itself M eff (GeV) Frank E. Paige 17 LC Physics in LHC Era

18 Discovery of /E T signature at 1TeV possible in 1 month [Denegri]: 14 g(3) L dt = 1, 1, 1, 3 fb -1 A =, tanβ= 35, µ > 12 CMS miss E T (1 fb -1 ) miss E T (3 fb -1 ) h(123) 1 g(25) one m 1/2 (GeV) 8 6 TH Ωh 2 =.4 q(2) g(15) g(2) miss E T (1 fb -1 ) q(25) one 4 Ωh 2 = 1 q(15) miss E T (1 fb -1 ) g(1) one one 2 q(5) h(11) EX Ωh 2 =.15 g(5) q(1) cosmologically plausible region Fermilab reach: < 5 GeV DD_ m (GeV) Frank E. Paige 18 LC Physics in LHC Era Catania 18

19 14 12 E miss T q (25) (3 fb -1 ) SUSY cascade decays give many inclusive signatures [CMS]: /E T + jets. TH E miss T no leptons g (3) CMS 1 fb -1 h (123) g (25) /E T + jets /E T + jets + 1. /E T + jets + /E T + jets +.. m 1/2 (GeV) 8 6 q (2) 2 OS 2 SS g (2) g (15) Problem at LHC is not to observe SUSY but to separate channels and to measure masses and other properties. 4 2 q (5) h(11) EX g (5) q (1) q (15) g (1) visibility of dilepton structure D_D_1266c.mod m (GeV) Frank E. Paige 19 LC Physics in LHC Era

20 Good strategy: identify and measure kinematic endpoints [Hinchliffe... ]. E.g., χ 2 χ1 dilepton endpoint measures M χ M χ1. 2 Dilepton distributions for χ 2 and χ2 χ1z [CMS]: 25 m = 9 GeV, m 1/2 = 22 GeV µ >, A = 5 m = 15 GeV, m 1/2 = 25 GeV µ >, A = Events / 4 GeV / 1 fb e ± µ tanβ = 2 tanβ = 35 e + e -,µ + µ ± Events / 4 GeV / 1 fb e + e -,µ + µ e ± µ ± M(I + I - ) (GeV) SM 1 2 M(I + I - ) (GeV) 3 Blois 2 Can use shape of distribution to distinguish sources. Frank E. Paige 2 LC Physics in LHC Era

21 Long decay chains allow more measurements. At SUGRA Point 5 q L R q χ1 q is dominant source of χ 2. Can combine leptons with two hardest jets to form endpoints M 1 M, q M 2 q and threshold T cm max. Can then solve for masses [Allanach... ]: 2q χ q for M q, O1 S ')(+* $&%!#" -,. /132 / ;:=< >@? ACB=D Frank E. Paige 21 LC Physics in LHC Era

22 Have now examined many SUSY points for LHC. General assessment: SUGRA in main region giving CDM has light sleptons, so enhanced lepton decays. Generally like above case. GMSB models are generally easier. AMSB models are comparable to SUGRA, but no 1 signatures. Models with tanβ 1tend to decay to τ s. Harder, but can potentially measure τ polarization chiral structure. SUGRA models in focus point region give complex signatures, e.g., g χ12tb, with many jets and leptons. R-parity violation: χ 1 cds decays are quite difficult. L-violating decays are generally easy, except perhaps for τ s. At least some endpoint measurements possible for all cases studied so far. But what is possible at LHC depends on entire pattern of SUSY masses and decays. Frank E. Paige 22 LC Physics in LHC Era

23 LC signatures much less model dependent if energy is sufficient. Strategy is to use kinematics to reconstruct missing χ 1. For e e with χ1 can determine masses from minimum and maximum E : Errors are 1% [Martyn]. For any visible SUSY particle can measure χ 1 1% in favorable cases at LHC. mass to 1%. Compare to Frank E. Paige 23 LC Physics in LHC Era

24 Important to include γγ background. Can remove with p T 4GeV cut. Signals for right and left polarization from Colorado study with undergraduate students [Nauenberg... ]: Number of Events Number of Events Energy of e + /e - GeV Energy of e + /e - GeV If both and L R produced, then can cancel γγ background with double subtraction method. Also reduces systematic errors. Frank E. Paige 24 LC Physics in LHC Era

25 Precision SUSY tests with slepton masses possible, e.g., M 2 L M 2 R 5M 2 2 M2 ν M 2 L M 2 W cos2β χ 2 =1 M 2 ( GeV 2 ) 2 Universal Scalar Mass A M el M er (GeV 2 ) But may have ν ν χ1 as at SUGRA Point 5. Frank E. Paige 25 LC Physics in LHC Era

26 Can apply similar analysis to reconstruct χ 1 χ1qq : 18 Events e + e χ+χ 1 1 s = 5 GeV 2 fb 1 (a) Mχ 1 (GeV) χ (b) Input E jj (GeV) Mχ 1 (GeV) 775A11 Chargino sector depends only on µ, M 2, tanβ, and M νe for σ χ Many observables: M χ, σ R, A FB 1 R, σ L, A FB L. Detailed analysis possible for both charginos and neutralinos even including CP violation [Kalinowski]. 1. Frank E. Paige 26 LC Physics in LHC Era

27 Ultimate goal is to determine entire SUSY spectrum. Then use RGE s to extrapolate to high Q 2, rather than fitting to specific model. Example using estimated errors for LHC and LC-5 reconstructs SUGRA unification at GUT scale [Blair]. Requires at least q, g from LHC and precise χ 1, slepton, and gaugino measurements from LC. Frank E. Paige 27 LC Physics in LHC Era

28 LHC should find SUSY if it exists at TeV scale. Emphasizes q, g, and their decay products. No signal in a year LC unlikely to see SUSY. LC potentially measures and lighter χ well, including especially no reliable estimate of required s. χ 1 χ1. But mass at LC might allow extraction of individual masses from decay chains at LHC. Branching ratios for χ 2 and χ 1 from LC would facilitate extraction of q and q χ2q χ 1 q at LHC. τ signatures are important but difficult. Probably easier at LC because of CCD vertexing and less soft background. More study needed. Frank E. Paige 28 LC Physics in LHC Era

29 Precision Physics: Giga-Z LC could produce 1 9 Z s per year. Could redo LEP every day with polarization. current bound m t α Also precise W and t masses from threshold scans LEP/SLC/Tevatron Need e and e polarization to control A LR systematics [Blondel]. Would give extremely precise test of SM [Heinemeyer] GeV 15 GeV 12 GeV LEP/SLC/LHC GigaZ Any disagreement between measured ellipse and SM trapezoids new physics Frank E. Paige 29 LC Physics in LHC Era

30 Conclusion Precision electroweak tests of SM strongly suggests light Higgs. LHC should find Higgs, measure mass and some couplings. LC clearly better for measuring Higgs couplings. Strongest argument to proceed with LC now. Expect new physics at TeV scale beyond SM Higgs: SUSY, or perhaps something quite different. LHC should discover it and provide many measurements. LC can provide better measurements of accessible SUSY particles, particularly χ 1 and. But do not know required s. Combination of LC and LHC measurements seems essential. Essential both to sharpen physics case and to demonstrate technology if we are to build LC in timely fashion. Frank E. Paige 3 LC Physics in LHC Era