Searching for Fermiophobic Higgs in OPAL Data: Signal Channels and Background Analysis

1. Searching for fermiophobic HIGGS in OPAL data.

2. What is the femiophobic Higgs. • Doesn’t couple to fermions. • Couples just to vector bosons. f H f Z* W* g H H H W Z g

3. Higgs production. • Higgsstruhlung is the main production channel. • In eejjjj and ee jjjj vector boson fusion interferes. • Three possible final states: • ZH->ZWW • ZH->ZZZ • ZH->Zgg • We consider first two channels (two photon channel has been considered by the OPAL collaboration already) • Each of vector bosons decays into two fermions->6 fermion final state.

4. Main Signal Channels

5. Higgs production. • The main channels are: (ZWW)->… • Z->jj channels (multihadronic) • W->jj;W->jj 6 jet channel26.83 events • W->jj;W->l 4 jets+l+ channel25.04 events • W->l;W->l 4 jets + 2l channel5.84 events • Z-> missing energy channels (missing energy) • W->jj;W->jj 4jet + Emiss channel 9.35 events • W->jj;W->l 2jet + l + 3 channel 8.72 events

6. 1 lepton channels We look at 1l channels: • Multihadronic channel • W->jj;W->l 4 jets+l+ channel25.04 events • Missing energy channel • W->jj;W->l 2 jets+l+Emiss channel8.72events • The lepton can come either from on-shell W or from of-shell W*. Of course, those leptons have different energies. So, for each channel we split our analysis into two parts: hard lepton and soft lepton part.

7. That how it looks.

8. Our channels • Our channels: • 1l multihadronic high pt channel • 1l multihadronic low pt channel • 1l missing E high p channel • 1l missing E low p channel • 2l multihadronic channel • 4q missing E channel • 6q multihadronic channel

9. Background. • High multiplicity bg • 2q • WW->qqlEmiss;WW->qqqq • ZZ->qqll; ZZ->qqEmiss;ZZ->qqqq • gg

10. The analysis: channel by channel: 1l multihadronic high E channel • 1 isolated lepton high pt lepton pl>25GeV • Pt>15GeV to reduce  • Nc>15 to reduce low multiplicity events • Eobs>150GeV to separate from Emiss events • Y23>0.25 to ensure at least three jets • Event is split into three jets. Each of them should contain at least 3 charged tracks. Reduces  bg. • Mw*1.3<mr<150GeV. Where mr is the mass of the system which recoils against lepton. To reduce ZZ and WW bg. • Pr<sqrt(2/4-MW2)-0.2*MW

11. The analysis: channel by channel: 1l multihadronic low E channel • 1 isolated lepton high pt lepton 8<pl<25GeV • Pt>15GeV to reduce  • Nc>10 to reduce low multiplicity events • Eobs>150GeV to separate from Emiss events • Y34>0.15 to ensure at least four jets • Event is split into three jets. Each of them should contain at least 3 charged tracks. Reduces  bg. • Mr>1.6mW • ml>10GeV, where ml is the invariant mass of the lepton neutrino system. This cut reduces tau bg.

12. The analysis: channel by channel: 1l missing E high E channel • 1 isolated lepton high p lepton pl>25GeV • Pt>15GeV to reduce  • Abs(pz)<40GeV and fw<2GeV and sw<5GeV and gc<5GeV to reduce  • Nc>3 • Eobs<85GeV to separate from Emiss events • M’W’>0.85mW where M’W’ is the reconstructed mass of the W boson, assuming signal scenario. • Event is split into two jets. E1/E2<5, where E1 and E2 are jet’s energies. To kill events, containing soft leptons misidentified as jets.

13. The analysis: channel by channel: 1l missing E low E channel • 1 isolated l low E lepton 3<El<25GeV • Pt>15GeV to reduce  • Abs(pz)<40GeV and fw<2GeV and sw<5GeV and gc<5GeV to reduce  • Nc>3 • Eobs<120GeV to separate from Emiss events • Pr<sqrt(2/4-MW2)-0.1*MW • 10GeV<ml<60 GeV, where ml stands for the invariant mass of l and  system. Lower cut kills taus. Upper cut kills WW and ZZ bg. • 0.2-0.1*(mH-105)<cos(ljj, )<0.65-0.1**(mH-105), where cos(ljj, ) stands for the angle between ljj system and the neutrino (assumning signal hypothesis is correct)

14. The analysis: channel by channel: 0l multihadronic 6 quark channel • 0 isolated leptons • <Pt> >50GeV. Events are spitted into 4 jets. Their average pt should be higher, than 50GeV. Very strong cut, used to kill ->4q. Usual usual Pt does not help here because of no missing energy. • Nc>25 to reduce low multiplicity events • Eobs>180GeV to separate from Emiss events • Y45>0.25 to ensure at least five jets • Event is split into three jets. Each of them should contain at least 3 charged tracks. Reduces  bg. • Events are splitted into 5 jets. Look for the pair with invariant mass, closest to Z mass. The difference should be not higher than 15 • After applying step 6, take remaining 3 jets and find the mass closes to that of W. The difference should be less, than 40

15. The analysis: channel by channel: 0l multihadronic 4 quark channel • 0 isolated leptons • Pt>15GeV • Pz and fw cuts • Nc>25 to reduce low multiplicity events • 100<Eobs<120GeV to separate from Emiss events • Mvis>MW*1.2. The invariant mass of event is Mh for the signal and mw for bg. • Pvis<sqrt(ecms**2-mw**2)-0.35*mw • Missing mass>Mz*0.9. To kill ww and ZZ bg.

16. The analysis: channel by channel: 2l multihadronic 2 quark channel • 2 isolated leptons • Pt>10GeV • Nc>5 to reduce low multiplicity events • Eobs<180GeV to separate from Emiss events • El1>25 and 3GeV<El2<25GeV. To isolate high and lot energy leptons. • Pr<sqrt(ecms**2-mw**2)-0.15*mz

17. Here we are done. Results for each channel for Higgs mass of 105GeV

18. Our and others results: We: Expected exclusion is at 105.9GeV Observed exclusion is at 108.2GeV (no ggStudy). OPAL:MH>105.5 GeV (just gg) channel. hep-ex/0212038 ? Somebody should combine these two studies: should not be difficult. A3: Expected exclusion for WW is at 107.5GeV Observed exclusion is at 104.6 GeV hep-ex/0204029 DELPHI:MH>104.1GeV (just gg) channel hep-ex/0406012 Combined gg: MH>109.7 GeV