John MarshallHZ Recoil Mass1 HZ Recoil Mass Analysis: Production Requests LCD WG6 Meeting, 28/02/2012 J.S. Marshall, University of Cambridge

John MarshallHZ Recoil Mass2 CDR V3 Benchmark Process  s = 500GeV L int = 500fb -1 m H =120GeV No polarization Relevant processes for this study are the recoil reaction e + e -  HZ  Hff, commonly called Higgs-strahlung. By detecting decay products of the Z, can search for Higgs signals without further assumption about Higgs decay modes: “model independent analysis”. For CDR V3, will search for decays Z  and Z  ee: “  X” and “eeX” channels. Signal is selected by identifying two well- measured leptons in final state, yielding Z mass. Can then compute recoil mass:

John MarshallHZ Recoil Mass3 Analysis for ILD LoI Very similar analysis was performed for the ILD Letter of Intent: Excellent starting point for considering MC samples required for the analysis:  s = 250GeV L int = 250fb -1 P e- = -80% P e+ =+30% *signal samples generated to yield L int = 10ab -1 Process description Cross-section Cross-section after pre-cuts Events simulated Eff. selection cross-section  X (signal) fb 116,700*6.38 fb  pb84.86 fb 2.1  fb  fb 1.6   fb 1.2  fb  ff fb 3.0  fb eeX (signal)12.55 fb 125,500*4.61 fb ee17.30 nb57.14 fb 8.9  fb  fb 1.6  fb ee fb 1.6  fb eeff fb 1.1  fb

John MarshallHZ Recoil Mass4 Analysis for CLIC CDR V3 Process description Whizard process ID Cross-section Required events  X (signal) hzmumu2.18 fb54,500*  e2e fb 2.3  10 5  e3e fb 2.3  10 5  e2e2nn fb 8.0  10 4  ff e2e2ff fb 2.3  10 6 eeX (signal)hzee2.18 fb54,500* eee1e nb 8.7  10 9  e3e fb 2.3  10 5 ee eenunu fb 2.1  10 5 eeff e1e1ff fb 3.0  10 6 *signal samples requested to yield L int = 25ab -1 Cross-sections for the signal and background processes relevant to analysis for CLIC CDR V3 obtained from Whizard (thanks to Stephane for providing binary with relevant processes). Set parameters: sqrts=500, USER_spectrum_mode=  13 for correct beam simulation, mH=120GeV for signal samples, mH=12TeV for background. Select desired process and run: m  m recoil Examine stdhep files

John MarshallHZ Recoil Mass5 2-Fermion Backgrounds Looking into ILD LoI study in more detail, see that 2-fermion background were reduced to negligible levels. If computing resources are stretched, could justify neglecting production of 2-fermion background samples. Number of events left after each cut.  X eeX

John MarshallHZ Recoil Mass6 4-Fermion Backgrounds Process description Fraction passing cut: p T l+l- > 10GeV + Additional cut: |cos  l+ / l- | < Additional cut: (71.18 <M ll < 111.8) GeV  X (signal) 100.0%97.0%92.7%  15.3%14.6%0.0%  84.2%73.2%48.5%  ff 22.6%16.9%2.6% eeX (signal)99.8%96.9%88.6% ee4.0%2.0%0.0% ee 90.8%69.4%39.8% eeff 69.0%32.5%26.5% Largest remaining requests are the 4-fermion background samples. Investigate a few simple generator-level cuts to help save computing resources in generation of these samples. Use stdhepcut package, adding simple lepton p T and invariant mass cuts, in style of existing lepton angle cut class i.e. same function call to find leptons, no cuts made if >2 leptons match criteria. As initial reaction, suggest application of p T l+l- and |cos  l+ / l- | pre-cuts to  ff and eeff samples.

John MarshallHZ Recoil Mass7 Request Summary Process description Whizard process ID Cross-section Cross-section after pre-cuts Events requested  X (signal) hzmumu2.18 fb 54,500  e2e2nn fb 8.0  10 4  ff e2e2ff fb fb 3.9  10 5 eeX (signal)hzee2.18 fb 54,500 ee eenunu fb 2.1  10 5 eeff e1e1ff fb fb 9.8  10 5 Generator-level cuts for background samples  ff and eeff p T l+l- > 10GeV, cut on transverse momentum, calculated from vector sum of two leptons |cos  l+/l- | < 0.95, cut on angle of either of leptons