![cdf](cdf_ii_logo2.gif) |
INCLUSIVE PP
DIFFERENTIAL CROSS-SECTIONS
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Authors:
Manuel Mussini, Niccolo' Moggi
and Franco Rimondi
University and INFN, Bologna
for the CDF
Collaboration
Abstract
We present a measurement of the
inclusive charged particle pT and ΣEt differential cross section in
Minimum-Bias proton-antiproton interactions at sqrt(s)=1960 GeV. The
correlation of the particle average transverse pT with the particle
multiplicity in the event is also reported. Results are based over 506pb-1 of
CDF RunII data and corrected to hadron level. These measures give some of the
basic features if the inelastic-non-diffractive particle production
spectra.
Blessed plots in brief
Data were collected
with the Minimum-Bias trigger in low instantaneous luminosity conditions.
Efficiency and acceptance of the trigger have been measured by comparison with
a 0-bias sample. Vertex and track reconstruction efficiency were computed with
a Pythia tuneA run-dependent MC sample. The calorimeter response to the event
ΣEt was also measured with MC.Tracks are selected in
pT>0.4 GeV. Both tracks and ΣEt in |η|<1.
The
track pT differential cross section
d3σ/pTdΦdydpT.
This measure extends the spectrum range a factor 15 wider than the
previous CDF measure in 1989. The differential cross-section now spans
over 11 orders of magnitude.
In the plot below is shown the total uncertainty: statistical (solid
line) and systematic (yellow
band).
(click on the image on the right for a
high resolution eps file)
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The
convolution of all corrections applied is reflected in the overall
variation of the raw to the corrected spectrum as shown here.
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Here
is shown how the function used in Run0 to fit the region [0.4 - 10] GeV
becames inadequate at higher pT. The dotted line is the Run0 fit. The
continuous green line a fit to the present data in the same limited
region.
f = A ( p0 / pT+p0 ) ^n
The
same power-law function cannot be employed for a fit to the whole
spectrum.
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![](dsdpt_fit_pub.gif) |
Correlation of the average track pT with the event
multiplicity (number of primary tracks). RunII measure is compared with
RunI and gives no indication of structures at high multiplicities as
may be expected in some non-perturbative production
models.
In this plot are used also events collected from a special
"high-multiplicity" trigger which selects Minimum-Bias interactions
with more that 23 tracks converging to the primary vertex and no other
requirements.
Statistical and systematic uncertainties are shown
in the lower plot.
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![](ptm_pub.gif) |
Same
plot compared to the Pythia (tuneA) Min-Bias particles production.
Regardless all the improvements in the comprehension of low-pT
production, the models are still unable to reproduce second order
quantities such as final state particle correlations.
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![fig5](ptm_pythia_pub.gif) |
MC with full
calorimeter simulation is employed to evaluate the response of the
central calorimeter to the event ΣEt. |
![](sumetabscor_pub.gif) |
The
raw ΣEt distribution undergoeas a number of corrections. The most
important is shown above and requires that the corredted distribution
is "unfolded" to correct for smearing among bins. The unfolding factor
is computed with a sample of MC re-weighted to best reproduce the data
distribution. |
![](sumetunfold_pub.gif) |
The
ΣEt cross-section spectrum d3Et/dηdΦdEt.
The (transverse) energy
is measured in the central region only as the sum of the Et of each
calorimeter tower in |η|<1. This plot shows the fully
corrected distribution. Statistical (solid line) and systematic
uncertainties (yellow band) are shown below.<1). the plot shown
is the fully corrected distribution. Statistical (solid line) and
systematical uncertainties are shown below.
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![](dsdet_pub.gif) |
The
measure of the sum Et is very sensitive to multiple interactions. For
this reason we selected only crossings with only one reconstructed
primary vertex and limited the analysis to the very low-luminosity
runs. Still, some undetected multiple interactions remain (mostly cases
of overlapping vertices). We can evaluate their amount by studying how
the average track multiplicity varies with the instantaneous
luminosity. The effect of multiple interactions is then corrcted
for. |
![](multlum_pub.gif) |
this page by niccolo' moggi (moggi@fnal.gov)
last update: 2008/05/06