How to control production of Ks using all tracks

How to control production of Ks using all tracks

A new way of making Ks using all type of tracks has been introduced in DaVinci v9r0, via the

package Phys/Ks2PiPiSel v1r0.

Example options for tight or loose selection are provided in $DAVINCIROOT/options and are

included as example in DaVinci.opts.

DaVinciKshortLoose.opts contains

//--- loose Ks Selection

ApplicationMgr.DLLs += { "Ks2PiPiSel" };

#include "$KS2PIPISELROOT/options/PreLoadPions.opts"

#include "$KS2PIPISELROOT/options/Ks2PiPi.opts"

#include "$KS2PIPISELROOT/options/KsCheckMC.opts"

DaVinciKshortTight.opts contains

//--- tight Ks Selection

ApplicationMgr.DLLs += { "Ks2PiPiSel" };

#include "$KS2PIPISELROOT/options/PreLoadPions.opts"

#include "$KS2PIPISELROOT/options/bestKs2PiPi.opts"

#include "$KS2PIPISELROOT/options/KsCheckMC.opts"

Three types of pions are loaded in PreLoadPions.opts and stored at

"/Event/Phys/UpstreamPion"

"/Event/Phys/LongPion"

"/Event/Phys/VTTPion"

Loose or tight selection of 4 types of Ks are done with the option file Ks2PiPi.opts or bestKs2PiPi.opts.

The output locations are

"/Event/Phys/LLKs"

"/Event/Phys/UUKs"

"/Event/Phys/LVKs"

"/Event/Phys/LUKs"

TrTransporter is used for KsAlgorithm.ParticleStuffer with TrHerabExtrapolator as the extrapolator.

Finally the check of performance is done in KsCheckMC.opts for 4 types of Ks separately and

histograms are put in separate directories .

The KsReco package in longer in DaVinci as it is not compatible with the new package.

Users are recommended to try the tight selection as the cuts are carefully chosen based on the monitoring algorithm so that any source of severe background is (tried to be) removed with not too big loss of efficiency. Especially ks background from prompt tracks are rejected by a tighter zKsMin cut. And the pt cut is chosen to be small (50 MeV) for LL and LV and lager for UU and LU.

However, if users intend to choose their own cuts according to their special situation, they can start from the loose selection and then tighten some options.

A new type of ks is selected: long + upstream tracks. As expected, the number of true ks in this catogery is small (<10% of UU), while the background is higher than the LV case. Anyway, it can be tried.