Measurements of longitudinal and transverse momentum distributions for neutral pions in the forward-rapidity region with the LHCf detector

Abstract

The differential cross sections for inclusive neutral pions as a function of transverse and longitudinal momentum in the very forward rapidity region have been measured at the Large Hadron Collider (LHC) with the Large Hadron Collider forward detector (LHCf) in proton-proton collisions at √ s = 2.76 and 7 TeV and in proton-lead collisions at nucleon-nucleon center-of-mass energies of √ sNN = 5.02 TeV. Such differential cross sections in proton-proton collisions are compatible with the hypotheses of limiting fragmentation and Feynman scaling. Comparing proton-proton with protonlead collisions, we find a sizable suppression of the production of neutral pions in the differential cross sections after subtraction of ultra-peripheral proton-lead collisions. This suppression corre-arXiv:1507.08764v3 [hep-ex]

AAfrag: Interpolation routines for Monte Carlo results on secondary production in proton–proton, proton–nucleus and nucleus–nucleus interactions

“…2, we plot the calculated spectrum of neutral pions in the c.m. frame together with the data of the LHCf experiment [13] for proton-proton collisions at 7 TeV c.m. energy.…”

“…Calculated invariant energy spectrum x E dn π 0 pp /dx F , with x E = 2E/ √ s, of neutral pions (red line) in the c.m. frame for pp-collisions at √ s = 7 TeV, compared to the data (black errorbars) of the LHCf experiment[13]. Calculated rapidity distributions dn/dy of antiprotons (solid red lines) and antineutrons (dashed blue lines) for pp-collisions at different incident momenta (from left to right: 31, 40, 80, and 158 GeV/c), compared to NA61 data on p-production[14] (black errorbars).…”

Strong Interactions - Experimental Overview

“…The difficulty in obtaining a proper description of the forward energy flow has been also observed by the CMS experiment which compared the total energy measured in the range −6.6 < η < −5.5 in pp interactions at 13 TeV to various MC generators [14]. Moreover, while the data taken at different √ s at the LHC indicate that Feynman scaling holds in the forward region [13,15], in the MC generators the scaling is pushed to the extreme forward region. This is shown in Fig.…”

“…The spectra of forward-produced neutrons [12] and π 0 [13] have been investigated by the LHCf Collaboration, whose calorimeters are located at ±140 m from the ATLAS interaction point. The aim of this experiment is the study at the LHC accelerator of the neutral-particle production cross sections in the very forward region of proton-proton and nucleus-nucleus interactions to provide essential input for understanding the development of atmospheric showers induced by very high energy cosmic rays hitting the Earth atmosphere.…”

On the threshold resummation in forward pA collisions

“…This implies that the so-called threshold logarithm can start to appear and become important in the dilute-dense factorization approach. In addition, the ultra-forward rapidity hadron spectrum has been measured recently by LHCf [22], which is sensitive to the very large x region of the projectile hadron and extremely small x region of the target nucleus [23]. In this case, we believe that the threshold resummation becomes indispensable.…”