From 8a6c5bd34676654ff830bd30642c61b86cdebd7c Mon Sep 17 00:00:00 2001 From: altsybee Date: Tue, 4 Nov 2025 14:33:09 +0100 Subject: [PATCH 1/2] small refinements in EventSelection.md --- docs/analysis-tools/EventSelection.md | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/docs/analysis-tools/EventSelection.md b/docs/analysis-tools/EventSelection.md index ec5f2176..9c14b951 100644 --- a/docs/analysis-tools/EventSelection.md +++ b/docs/analysis-tools/EventSelection.md @@ -465,7 +465,7 @@ A single-value "integrated" occupancy estimator for a given collision can be cal float occupancyByFT0C = col.ft0cOccupancyInTimeRange(); // range: from 0 up to ~150k ``` -Notes: +_Notes:_ - Both occupancy estimators are pre-calculated per each collision in the event selection routine, [EventSelectionModule.h](https://github.com/AliceO2Group/O2Physics/blob/daily-20251029-0000/Common/Tools/EventSelectionModule.h#L1361). - In the occupancy calculation, multiplicities of nearby collisions are "weighted" according to their time separation from a collision-of-interest, to reflect the "severity" of their influence on that collision - Estimators return `-1` if a given collision is close to Time Frame borders (so, not enough information for the occupancy calculation, while we need information within -40 µs...+100 µs time range wrt a given collision), event loss ~1.2%. @@ -475,7 +475,7 @@ Notes: In addition to the occupancy estimators described above, several special event selection bits are implemented to better clean up various nearby effects from other collisions (related not only the TPC but also the ITS, e.g. due to high occupancies in the ITS Readout Frames). -The following table summarizes the event selection bits used to mitigate occupancy effects in Pb-Pb: +The following table summarizes the event selection bits that can help to mitigate the occupancy effects: | **Bit** | **Definition** | **Strictness** | **Typical Effect / Event Loss** | |---------|----------------|----------------|--------------------------------| @@ -516,6 +516,8 @@ Note that TPC-related occupancy effects are most pronounced in Pb–Pb runs, how - These dead periods correlate also with **drops in ITS–TPC matching efficiency**. - The effect appears both in **A-A** and **pp** data. +For more details, see the [report at DPG AOT meeting, Jan 2025](https://indico.cern.ch/event/1493023/#3-rejection-of-events-with-dea). + ### Using special event selection bits To reject events recorded during the affected time intervals, several event selection bits were introduced in O2Physics ([PR #9038](https://github.com/AliceO2Group/O2Physics/pull/9038), Dec 2024): From 505085f38b3031a2ac287bd6c750d3e002527239 Mon Sep 17 00:00:00 2001 From: altsybee Date: Wed, 5 Nov 2025 14:15:46 +0100 Subject: [PATCH 2/2] refinements in the text --- docs/analysis-tools/EventSelection.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/docs/analysis-tools/EventSelection.md b/docs/analysis-tools/EventSelection.md index 9c14b951..2101c4b3 100644 --- a/docs/analysis-tools/EventSelection.md +++ b/docs/analysis-tools/EventSelection.md @@ -480,7 +480,7 @@ The following table summarizes the event selection bits that can help to mitigat | **Bit** | **Definition** | **Strictness** | **Typical Effect / Event Loss** | |---------|----------------|----------------|--------------------------------| | `kNoCollInTimeRangeNarrow` | Rejects events if another collision within **±0.25 µs** | Narrow veto | Useful to suppress residual BC mis-associations; minimal event loss, ~1-1.5% | -| `kNoCollInTimeRangeStandard` | Rejects if: (1) another coll. within ±0.25 µs, or (2) multiplicity of a coll. in dt −4…+2 µs > threshold | Medium | Further suppression of effects from nearby collisions; ~3-7% event loss depending on IR | +| `kNoCollInTimeRangeStandard` | Rejects if: (1) another coll. within ±0.25 µs, or (2) multiplicity of a coll. in delta time −4…+2 µs > threshold | Medium | Further suppression of effects from nearby collisions; ~3-7% event loss depending on IR | | `kNoCollInTimeRangeStrict` | Rejects events if another collision is within **±10 µs** | Very strict | Strongly reduces effects from nearby events; large loss of statistics at high IR (can exceed 30–40%) | | `kNoCollInRofStrict` | Rejects events if >1 collision in the same **ITS Readout Frame** (~15 µs in Pb-Pb) | Very strict | Removes in-ROF pileup; at 38 kHz Pb–Pb cuts ~35% of events | | `kNoCollInRofStandard` | Allows >1 collision per ROF but rejects if another has multiplicity > threshold (default: FT0C amplitude >5000 a.u. ≈ 500 tracks) | Medium | Retains more stats, but protects against large in-ROF pileup |