Add HLT2 line Bu2DspPPbar

Add one HLT2 line of B^{+}\to D_{s}^{+}p\bar{p} for spectroscopy study.

The rate is estimated by hlt1_filtered 2024 minbias samples as

rate_MinBias_BuToDspPPbar
#= 1110033.0 Sum= 83.0 Eff = ( 0.007 +/- 0.001 )% | rate = ( 89.7 +/- 9.8 ) Hz

The related builders are quoted from b_for_spectroscopy and c_to_hadrons.

Given the fact there is no need for persistreco, this line isn't included in the make_Bu containter, but taken as an independent line and registered in hlt2_bandq directly.

And its mass for b-meson extends to cover the Bc mass since the rate is still within the limit.

FYI @jfu

Hlt/Hlt2Conf/python/Hlt2Conf/lines/bandq/builders/b_for_spectroscopy.py

@@ -260,6 +260,14 @@ def make_kaons_from_b():
         pt_min=pt_min_from_b, p_min=k_p_min_from_b)
 
 
+def make_protons_from_b():
+    return charged_hadrons.make_detached_protons(
+        pt_min=150. * MeV,
+        p_min=1. * GeV,
+        mipchi2dvprimary_min=4,
+        pid=F.require_all(F.PID_P > 5., (F.PID_P - F.PID_K) > 0.))
+
+
 #------- Charm hadrons, tight versions specifically to build B-hadrons
 import Hlt2Conf.lines.bandq.builders.c_to_hadrons as c_to_hadrons
 make_Dz = c_to_hadrons.make_tight_Dz
@@ -497,6 +505,17 @@ def make_BuToDmPiPi(process):
     )
 
 
+@configurable
+def make_BuToDspPPbar(process):
+    protons = make_protons_from_b()
+    ds = c_to_hadrons.make_DspToKmKpPip()
+    return make_b2cx_for_spectroscopy(
+        particles=[ds, protons, protons],
+        am_max=6400 * MeV,
+        m_max=6320 * MeV,
+        descriptor='[B+ -> D_s+ p+ p~-]cc')
+
+
 @configurable
 def make_BdToDmPip(process):
     pion = make_pions_from_b()