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Trigger Criteria for Level 1

Trigger Criteria for Level 1. Joel Butler. Objective. The use of the requirement of “N” detached tracks EACH with impact parameter greater then “M” standard deviations as the Level 1 requirement has been with us from the earliest days of the Level 1 Trigger development

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Trigger Criteria for Level 1

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  1. Trigger Criteria for Level 1 Joel Butler

  2. Objective • The use of the requirement of “N” detached tracks EACH with impact parameter greater then “M” standard deviations as the Level 1 requirement has been with us from the earliest days of the Level 1 Trigger development • It is natural to ask whether • Some other criteria would have somewhat improved efficiency. Possible gains are small for B’s but potentially large for charm where efficiency is low • What effect this trigger criteria has on the proper time distribution (an effect of the current trigger first observed by Harry Cheung) and whether some other criteria would have a smaller effect.

  3. Game Plan • Study the effect on the efficiency and proper time distribution for our usual trigger for “typical states” of B and charm decay • Study alternatives

  4. Trigger Efficiency B-->D*p for Final Signal Events

  5. Trigger Efficiency for B-->D*p for all signal events

  6. Normal Trigger Level 1 Trigger Efficiency For generated minbias: Upper left: 300 MeV/c Upper right: 500 MeV/c Lower left: 700 MeVc

  7. Proper time for B-->D*p Affect of proper time Resolution seen clearly In untriggered curve to 1 ps and to triggered through whole distribution

  8. Reduced proper time for B-->D*p No trigger t’ = t - Ns where N is the L/s cut L1 Trigger It means you start the decay clock after Ns. This works only if s does not depend on t. This is useful for lifetime measurements but not for mixing where the interaction starts the clock. The lifetime fit with no trigger Is very close to the MC value.

  9. Fit Results The result of the fit to the “untriggered” t’ distribution: 1.67ps The result of the fit to the “triggered” t’ distribution: 1.98ps The uncertainty is about 0.02. One can probably do a bit better By tailoring the ranges, but the f(t’) will still not be flat. Nothing here is fatal but it would be very good to improve the situation

  10. Conclusion from B study • The trigger affects the time distribution requiring “f(t)” corrections. These are always subject to complaint and should be kept as small as possible

  11. Charm Study • Study undertaken with directly produced Do--> Kp. • Used a “candidate driven” algorithm to build the primary vertex for each candidate D. This is the first time I have a completely “unprompted” analysis. Valid only for all charged final states • Consider also Pt cut on “detached” candidates

  12. Level 1 Trigger Efficiency For generated CCBAR: Upper left: 300 MeV/c Upper right: 500 MeV/c Lower left: 700 MeVc

  13. Level 1 Trigger Efficiency For generated D0-->Kp: Upper left: 300 MeV/c Upper right: 500 MeV/c Lower left: 700 MeVc

  14. Charm • Pt cuts cause less trouble than I would have imagined • The “standard” trigger has an efficiency of around 10%, which is not bad. Roughly, speaking, the “effective” charm luminosity is 15-20% of the B luminosity • Improvements would be welcome

  15. In progress • Change trigger criteria • Require two tracks each with M>3 • Require sum of normalized detachment squared greater than some number, like 72 (2X62) and then explore from there

  16. Sum of normalized impact parameters squared for all detached tracks associated with each primary Each track must have at least 3 s, which for two tracks gives 9, so a sum of 18 min is already required

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