Thu·Jun 11, 2020Thursday·June 11, 2020

1. 01*

   Review of results using heavy ion collisions at CMS

   Georgios Konstantinos Krintiras (on behalf of the CMS Collaboration)🇺🇸

   Ultrarelativistic heavy ion collisions at the laboratory provide a unique chance to study quantum chromodynamics (QCD) under extreme temperature ($\approx 150\mathrm{MeV}$) and density ($\approx 1\mathrm{GeV}/{\mathrm{fm}}^3$) conditions. Over the past decade, experimental results from LHC have shown further evidence for the formation of the quark-gluon plasma (QGP), a phase that is thought to permeate the early Universe and is formed in the high-density neutron-star cores. Various QCD predictions that model the behavior of the low-$x$ gluon nuclear density, a poorly explored region, are also tested. Since the photon flux per ion scales as the square of the emitting electric charge $Z^2$, cross sections of so far elusive photon-induced processes are extremely enhanced as compared to nucleon-nucleon collisions. Here, we review recent progress on CMS measurements of particle production with large transverse momentum or mass, photon-initiated processes, jet-induced medium response, and heavy quark production. These high-precision data, along with novel approaches, offer stringent constraints on initial state, QGP formation and transport parameters, and even parametrizations beyond the standard model.

   nucl-ex4 citations
2. 02*

   Systematic reduction of the proton-removal cross section in neutron-rich medium-mass nuclei

   J. Díaz-Cortés🇪🇸 · J. Benlliure🇪🇸 · J.L. Rodríguez-Sánchez🇪🇸 · H. Álvarez-Pol🇪🇸 · T. Aumann🇩🇪 · C.A. Bertulani🇺🇸 · B. Blank🇫🇷 · E. Casarejos🇪🇸 · D. Cortina-Gil🇪🇸 · D. Dragosavac🇪🇸 · V. Föhr🇩🇪 · A. Gargano🇮🇹 and 15 other authors

   Single neutron- and proton-removal cross sections have been systematically measured for 72 medium-mass neutron-rich nuclei around Z=50 and energies around 900A MeV using the FRagment Separator (FRS) at GSI. Neutron-removal cross sections are described by considering the knock-out process together with initial- and final-state interactions. Proton-removal cross sections are, however, significantly smaller than predicted by the same calculations. The observed difference can be explained as due to the knockout of short-correlated protons in neutron-proton dominating pairs.

   nucl-exnucl-thPLB(2020)·14 citations
3. 03*

   On a chi^2-function with previously estimated background

   Fernando M.L. Almeida Jr.🇧🇷 · Andre A. Nepomuceno🇧🇷

   There are intensive efforts searching for new phenomena in many present and future scientific experiments such as LHC at CERN, CLIC, ILC and many others. These new signals are usually rare and frequently contaminated by many different background events. Starting from the concept of profile likelihood we obtain what can be called a profile ${\chi }^2$-function for counting experiments which has no background parameters to be fitted. Signal and background statistical fluctuations are automatically taking in account even when the content of some bins are zero. This paper analyzes the profile ${\chi }^2$-function for fitting binned data in counting experiment when signal and background events obey Poisson statistics. The background events are estimated previously, either by Monte Carlo events, ``idle" run events or any other reasonable way. The here studied method applies only when the background and signal are completely independent events, i.e, they are non-coherent events. The profile ${\chi }^2$-function has shown to have a fast convergence, with fewer events, to the ``true'' values for counting experiments as shown in MC toy tests. It works properly even when the bin contents are low and also when the signal to background ratio is small. Other interesting points are also presented and discussed. One of them is that the background parameter does not need to be estimated with very high precision even when there are few signal events during a fitting procedure. An application to Higgs boson discovery is discussed using previously published ATLAS/LHC experiment data.

   ↳ hep-phhep-exnucl-exphysics.data-anBraz.J.Phys.(2020)·0 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.