Search for NMSSM Higgs at LHC in h → aa → mmmm signature

1. Search for NMSSM Higgs at LHC in h→aa →mmmm signature Alexander Belyaev (South Hampton) Jim Pivarski, Alexei Safonov, Sergey Senkin (Texas A&M)

2. Motivation • NMSSM is a viable extension of MSSM • Additional singlet superfield • Elegant solution to m problem of MSSM • Much less fine tuning and little hierarchy problem of MSSM • Fifth neutralino “singlino” can be consistent with WMAP • Expanded higgs sector • If Br(h1→a1a1) significant, softening of direct LEP limits on higgs • Large parameter space • Mostly explored region ma>2mt • Need large luminosity to directly detect (10-100 ifb), challenging experimentally • Region of ma<2mt not thoroughly explored • Clean signature of two pairs of collimated muons • Could be a near zero background early LHC search

3. Motivation II • Studies of the region ma>2mt show that this is a difficult analysis • Collimated pairs of tau or b jets make it challenging from experimental point of view, large backgrounds force to use VBF production • Need 10-100 ifb • Strictly speaking, there is no reason not to explore the ma<2mt region • Process pp→h1+X→a1a1+X • Can rely on muons if Br(a1→mm) is large enough • Experimentally very easy analysis (although a few tricks are required), low backgrounds, can use all higgs production modes • Lack of missing energy allows direct measurement of ma1, mh1

4. Analysis Strategy • In the region of interest these events appear as two collimated di-muon pairs • Relatively simple topology • Many constraints: • m(mm)=m(a1) m(mmmm)=m(h1) • Benchmark using CMS detector TDR • Also note sensitivity to dark matter light bosons * Analysis does not have to change if considering various production mechanisms, only acceptance will

5. Acceptance Estimates • Calculate acceptance using Pythia gg→h1 →a1 a1→mmmm • Grid in ma = 0.5-5 GeV, mh=60-120 GeV • Simple selections: • Require a muon w/ pT>20 GeV within |h|<2.4 • 3 more muons w/ pT>5 GeV within |h|<2.4 • Sort nearby opposite charge muons into pairs using DR(mm) • Large acceptance • of the order of 30-40% • Many ways to increase • e.g. tracks instead of some of the muons

6. m1234 m34 m12 Signal Shape • Signal: narrow 3D bump in (m12, m34, m1234) space • Background: mostly smooth function (next slide) • Symmetrize in m12 and m34

7. Backgrounds • E/weak pp->4l: CalcHEP • Negligible • QCD: • 2->2 Pythia • Leptons from heavy flavor, including J/psi • 20 events/100 ipb • Direct J/psi+X production (also Pythia) • Negligible • Fakes from QCD with misidentified muons • Use 2->2 Pythia with 3 leptons+track smearing with decay probabilities • Also around 20 evts/100 ipb • Background numbers normalized to “large” region • 0.5<m12<4 • 60<m1234<120

8. m1234 m34 m12 Sensitivity • Fit directly in 3D using binned likelihood for: • aS(m12, m34,m1234) +bB(m12, m34,m1234) • Background function comes from parameterizations on last page • Note that 0.4 background evts/ipb in full space • Fit looks for excess on the diagonal • There the background is tiny Ma=3 GeV Ma=2 GeV Ma=1 GeV

9. Branching of a to muons • Branching to muon is fairly independent of anything else • Muons compete with a→gg and lower with lighter quarks Obtained using NMSSMTools package

10. D-Zero Limit • D-Zero: direct 4mu search, similar to what we do: • Limit on sigma x BR of the order of 0.1pb • About 40 times smaller x-section given everything else equal (and acceptances are very similar): • 100 ipb LHC = 4 ifb TeV • LHC should quickly surpass Tevatron due to much higher x-section

11. Phenomenology • Now let’s look at what this means for NMSSM • Zoom into the region where ma is small • We started with gg→h1→a1a1 • Use NMSSMTools package for couplings • FeynHiggs for SM x-section

12. Parameter Space Controls coupling of new superfiled to SM • Navigate to the region with small ma and high Br(h→aa) • Avoid fine tuning, sort of go with the flow and see what happens

13. h1 Production and Decay 40-120 GeV • Scan in the selected range for production x-section of the lightest CP-even higgs h1 and Br(h1→a1a1) • Range used for the plot is mh=40-150 GeV • Scale SM Higgs x-sections (FeynHiggs) using couplings from NMSSMTools M(h1)~120 Two distinct scenarios for light a1: When m(h1) is light, it has strong coupling to light a1, decouples from SM; h2 is SM-like (~120 GeV) If m(h1) is a bit heavier, then it becomes SM-like higgs

14. CP-odd Higgs Decay • BR(a→mm)~10-20% for ma<2mt threshold • Largely independent of other parameters • Factoring in Br(h→aa), overall Br(h → 4m)~2-3%

15. Gluon Fusion x-section • We cut somewhat into the allowed space, but the preferred region has very small cross-section through gluon/b-fusion

16. Conclusions and Plans • Attractive and technically simple analysis, LHC will surpass Tevatron with just ~200 ipb • Have taken a look at the low m(a) scenario: • Still need to finalize the results, but it look like in the NMSSM parameter space allowing light ma, h1 becomes a singlet • Looking now into the pp→h2→h1h1 • If the branching ratio is large, may be able to see both a1 and h1 at LHC • If small, h1 will be hard to detect

17. Production Cross Section • NLO FeynHiggs: • NLO cross-section and width for SM higgs: • NMSSMTools: • Branching ratio for h1→gg, h1 width, reduced bbh1 coupling: