This is the list of the proposed standard AliFemto cuts.

event

---

fabs(AliESDEvent::GetPrimaryVertex()->GetZv())<7

Vertex z within 7 cm of the TPC center in the z direction
Do we need to restrict our events to 7 cm? If we use TPC only we can go further out, depending on the actual true distribution of z-vertex.-- AdamKisiel - 21 Jul 2008

AliESDEvent::GetPrimaryVertex()->GetZRes()<0.1

Error on vertex position estimation (z vertex resolution)

no cut on multiplicity (other than via the ZRes cut above)

track

---

AliESDtrack *track = AliESDEvent::GetTrack(i);

if (<nop>track-&gt;IsOn(AliESDtrack::kTPCrefit)) return 0;

require TPC refit

if (track->GetTPCNcls() < 120) return 0;

minimum number of TPC clusters

AliExternalTrackParam *tp = track->GetTPCInnerParam();
if (<nop>tp) return 0;

momenta and charges will be taken from TPCInnerParam. Reject tracks with no parameters at the entrance to the TPC.

chi2, as obtained via GetTPCchi2(), seems to look good for tracks with 120 clusters so maybe we do not have to cut on it explicitly.

Float_t r,z; 
track->GetImpactParameters(r,z); 
if (fabs(z)>0.2) return 0;

impact parameter in z

if (fabs(r)>0.1) return 0;

impact parameter in xy

-0.5 < eta < 0.5

Eta acceptance

Concerning the kt bins I propose to use the following values: 0.0-0.1 GeV 0.1-0.2 GeV 0.2-0.3 GeV 0.3-0.4 GeV 0.4-0.5 GeV 0.5-1.0 GeV (kt is defined as the vector sum of the two pt's, divided by two.) If you don't have kt bins then please just make sure that your kt range limits coincide with my bin limits, and I will sum up several bins. I am not sure if we can get particles below 0.1 GeV with TPC only information. I will reconfirm this with Marian Ivanov.-- AdamKisiel - 21 Jul 2008

pair

---

at least 2 cm separation at the entrance to the TPC (how do you do this?)
The TPC entrance and exit points of each track is stored in the AliESD. It can then be used to calculate the separation for each particle pair. An example of how to extract this information is located e.g. in AliFemtoEventReaderESDChain.cxx:435-442:

      esdtrack->GetInnerXYZ(xtpc);
      xtpc[2] -= fV1[2];
      trackCopy->SetNominalTPCEntrancePoint(xtpc);

      esdtrack->GetOuterXYZ(xtpc);
      xtpc[2] -= fV1[2];
      trackCopy->SetNominalTPCExitPoint(xtpc);

Where fV1 is an array holding the position of the event primary vertex (read from TPC only if needed).-- AdamKisiel - 21 Jul 2008

-- AdamKisiel - 21 Jul 2008