Motivation:

Followed the pp 500 GeV Year 2013 EEMC-dijet trigger & pp 500 GeV Year 2012 high tof multiplicity dihadron correlation where near-side Dphi distribution shows a bump with |Deta|>1.3. 
See: drupal.star.bnl.gov/STAR/blog/yili/pp-500-gev-year-2013-dihadron-correlation-eemc-dijet-data        
       drupal.star.bnl.gov/STAR/blog/yili/pp-500-gev-year-2012-dihadron-correlation-tofmult4tofmult3vpd-data

Similar result also seen in pythia simulation: drupal.star.bnl.gov/STAR/blog/yili/pp-510-gev-pythia-dihadron-correlation-hardqcd-20151007

Here is the MB trigger from pp 500 GeV Year 2012. 
 

See master page: drupal.star.bnl.gov/STAR/blog/yili/master-page-dihadron-pp-500-gev
 

Dataset:

pp 500 GeV 
Year 2012
filetype=daq_reco_MuDst,events!=0,trgsetupname=pp500_production_2012,filename~st_physics,production=P13ib,storage!=hpss,sanity=1
trigger id = 380002 -- VPDMB-nobsmd

Cuts:

|Vz|<50 cm 
nHits >= 25 points
nHits/nHitsPoss >=0.51
|dca|< 3 cm 
|eta|<1

Method:

Dihadron Deta-Dphi correlation. 

Not normailzed (a.u.). mixed event corrected. 

All TPC tracks are required to matched to BEMC of BTOF to reduce pileup effect. 

1<pT<3 GeV/c for both trigger and associated particles 

Mixed event:
<= 1 tracks difference in Ntrk in TPC
<= 1 cm difference in Vz

Result:

1. refmult distribution:
refmult is read from Mudst directly, not pile up removal matching. 
(events < 2 tracks are not included in histogram)

2. Delta eta distribution with |Delta phi|<1

3. Delta phi distribution with 1.3<|Delta eta|<1.5

4. Delta phi distribution with 1<|Delta eta|<1.5