Coherent pion analysis with garsoft: status report December 10, - - PowerPoint PPT Presentation

▶
coherent pion analysis with garsoft status report
SMART_READER_LITE
LIVE PREVIEW

Coherent pion analysis with garsoft: status report December 10, - - PowerPoint PPT Presentation

Feb 23, 2024 344 likes •490 views

Coherent pion analysis with garsoft: status report December 10, 2019 Leo Bellantoni MPD meeting From DESY workshop 135 CC coh + in 11 shifts of data Its a pretty plot Reverse the |t| cut & get 1 + ~60% pure for

slide-1
SLIDE 1

Coherent pion analysis with garsoft: status report

December 10, 2019 Leo Bellantoni MPD meeting

slide-2
SLIDE 2

2

From DESY workshop

  • 135 CC coh π+ in 11 shifts of

“data”

  • It’s a pretty plot
  • Reverse the |t| cut & get 1 π+

~60% pure for free

  • Reverse dE/dx cut & get

CCQE ~60% pure for free

  • Shows we can kill converted

pairs & ECAL background

  • Shown to LBNC last week

But! No overlaid inspill activity

slide-3
SLIDE 3

3

Adding overlays

  • GarSoft does not yet handle 10μs spill well – MC vertex can

be up to 10μs × 3cm/μs = 30cm closer to the endcap than the reconstructed vertex

  • I can match in the transverse plane fairly well
  • Now must loop over reco vertex & quiz matching MC

vertex; earlier I started at the MC vertex and found matching reco vertex

  • Therefore, have to change the definitions of my

backgrounds

  • What about tracks that cross the membrane & are late?

Then there are disconnected tracks and they might form vertices

  • Tom’s been stitching these, and I’ll talk about them later
slide-4
SLIDE 4

4

Adding overlays

  • Back-to-back verts killable with cos(ΘOPEN) > −0.90
  • Narrow angle cut more critical as there is signal there

I did a crude optimization on ~40% of the data

  • cos(ΘOPEN) < +0.98
slide-5
SLIDE 5

5

“Mystery” background

  • ~56 days of “data” (with downtime)
  • What’s that white “Mystery” background? It is

disconcertingly similar to the signal

  • It was in the Hamburg analysis, just not visible
slide-6
SLIDE 6

6

“Mystery” background

  • 1st look at events

shows that many of these are reco verts with no matching MC vertex

  • Only track quality cut

available is(basically) Nº TPCClusters – no χ2 available yet

  • Cut at ≥ 55 Clusters
slide-7
SLIDE 7

7

“Mystery” background

  • Helps but does not cure
  • A slightly prettier version of this plot might be

possible – this would be our “money” plot

slide-8
SLIDE 8

8

“Mystery” Background

  • Total 1113 events in the “Mystery” background
  • 209 actually can be matched to other kinds of MC

vertices than {RES, DIS, CCQE}:

  • In addition to good vertices from bad tracks we can also

have bad vertices from good tracks.

  • Only vertex quality cut available is distance between

trackends in the vertex – no χ2 available yet p – π−; I’ve seen Λs on smaller samples 106 pbar – π+ 2 π+ – π−, presumably from KS 74 e+ – e−. Remember that this is after the PTRACK > 150 MeV cut 26 π+ with some other thing 1

slide-9
SLIDE 9

9

  • Red line is reco verts that

match to MC vertices, black dots are ”Mystery” backgrounds (including those 209 that did match)

  • Pretty clear bias towards

bad reco verts in the unmatched reco verts

“Mystery” Background

slide-10
SLIDE 10

10

A Bump in the Middle

After the opening angle cut the membrane bump is still there, but smaller. Left, the before/after ratio when I do not require that there be an MC vertex matched back to the reco vertex; right, when I do.

slide-11
SLIDE 11

11

A Bump in the Middle

After the opening angle cut the membrane bump is still there, but smaller. Left, the before/after ratio when I do not require that there be an MC vertex matched back to the reco vertex; right, when I do.

We thought the shoulders here were delayed particles produced by GEANT. So why are they cos(ΘOPEN) ≅ ±1? These bumps have σ = 23.5 cm. Cut off distance between trackends to even be vertexed in the 1st place is 12 cm, half that. ∃ some background of bogus reco vertices with cos(ΘOPEN) far from ±1 and it is uniform in x,

slide-12
SLIDE 12

12

A Bump in the Middle

After the opening angle cut the membrane bump is still there, but smaller. Left, the before/after ratio when I do not require that there be an MC vertex matched back to the reco vertex; right, when I do.

It makes sense that “real” MC matchable vertices generally pass the -0.90 < cos(ΘOPEN) < +0.98 cut But why is there a bump still in the middle? There is supposed to be only 50 μm of material there, right? And why the dip before the bump? (These plots before the ΘFWRD, dE/dx, Nº TPC Cluster cuts)

slide-13
SLIDE 13

13

Conclusions / Discussion

  • I believe we know what these events are caused by
  • If it were a real dataset, it wouldn’t be ready for PRD
  • It will be hard to advance this analysis further

without sinking a lot of time into GArSoft, which would be a good thing to do actually

  • How to wrap this up into something for the CDR &

call it done?

  • How long a section in the CDR?
  • Could show the with-overlays plot or show the Hamburg era

plot and then talk about how overlays impact the analysis

slide-14
SLIDE 14

14

Backup

  • Hamburg analysis (no overlays) with new background

definitions