Alias particles in hadron decays

[Frank Siegert]

Request from LHCb: It would be useful to be able to define alias particles and their decay tables such that one can define signal decays similar to EvtGen.

[Frank Siegert]

Hi Julian,

I have implemented the alias functionality on our decays branch. I don't know whether it's worth trying to merge it into the current release/trunk, which would be possible, but a bit of work. How soon do you need this feature?

Does the alias functionality make the fixed decays feature obsolete? Then I would remove the fixed decays from the code.

Cheers, Frank

[Frank Siegert]

Replying to fsiegert:

I don't know whether it's worth trying to merge it into the current release/trunk, which would be possible, but a bit of work. How soon do you need this feature?

Actually it seems to be simpler than I thought. I have attached a patch against 1.2.x which allows you to use alias decays.

E.g. to create a signal decay chain B_s -> Jpsi phi -> mu mu K+ K- for all B_s signal particles (i.e. the ones that you have created with kfcode 7001 in your interface) you would create the following files:

---

Decaydata/HadronAliases.dat

7001->531   # create alias for B_s
7002->443   # create alias for J/psi
7003->333   # create alias for phi

---

Decaydata/AliasDecays.dat

7001    ->   Bs/      Decays.7001.dat    # add separate decay table for all 7001 B_s which
                                         # will make it always decay into 7002(jpsi) 7003(phi)
                                         # (see below)

7002    ->   Jpsi1S/  Decays.7002.dat    # add separate decay table for all 7002 Jpsi
                                         # making them decay into muons
                                         # (see below)

7003    ->   phi1020/ Decays.7003.dat    # add separate decay table for all 7003 phi
                                         # making them decay into K+ K-
                                         # (see below)

---

Decaydata/Bs/Decays.7001.dat

{7002,7003}  |  0.00135   |  Bs_Jpsi1Sphi1020.dat;   # assuming you want to use the same decay
                                                     # channel file as for normal Bs -> Jpsi phi

---

Decaydata/Jpsi1S/Decays.7002.dat

{13,-13}  |  0.0593(0.0006)[PDG]  |  Jpsi1S_mu-mu+.dat;  # again unchanged decay channel info

---

Decaydata/phi1020/Decays.7003.dat

{321,-321}  |  0.491(0.006) [PDG]  |  phi1020_K+K-.dat;  # again unchanged decay channel info

---

Does this look useful?

Frank

[Frank Siegert]

This is implemented in trunk r14835 and will be available in the next release.

[Stefan Hoeche]

Milestone old deleted