Musings on the current status of HEP

Abstract

In 2012 I published an article [1] presenting my personal views on the state of affairs in "our science," HEP theory. 1 That "old" article opens with a rather optimistic epigraph "Paraphrasing Feynman: Nature is more imaginative than any of us and all of us taken together. Thank god, it keeps sending messages rich on surprises." Has Feynman's prophecy come true?2012 was also the year of the Higgs boson discovery closing the age of the Standard Model (SM) confirmation. Now, seven years later, I will risk to offer my musings on the same subject. The seven years that have elapsed since [1] brought new perspectives: the tendencies which were rather foggy at that time became pronounced. My humble musings do not pretend to be more than they are: just a personal opinion of a theoretical physicist... For obvious reasons I will focus mostly on HEP, making a few marginal remarks on related areas.I would say that the most important message we have received is the absence of dramatic or surprising new results. In HEP no significant experimental findings were reported, 2 old ideas concerning Beyond the Standard Model (BSM) physics hit dead-ends one after another and were not replaced by novel ideas. Hopes for key discoveries at the LHC (such as superpartners) which I mentioned in 2012 are fading away. Some may even say that these hopes are already dead. Low energy-supersymmetry is ruled out, and gone with it is the concept of naturalness, a basic principle 3 which theorists cherished and followed for decades. Nothing has replaced it so far. 4 With the disappearance of this principle the issue of mass hierarchies becomes almost (if not completely) meaningless. 5 The Standard Model is still unchallenged: today no observed natural phenomena require its expansion. Dark matter composition is still a huge question mark.

The large-Nc limit of borelized spectral sum rules and the slope of radial Regge trajectories

“…In the limit of infinite Borel parameter, our borelized sum rule for the vector and axial channel becomes one of the usual planar sum rules which were considered many times in the past [9]. Indeed, taking the limit M 2 → ∞ in Eq.…”

“…The experimental information on the electromagnetic decay constants F n of radially excited light vector and axial mesons is poor. The quark-hadron duality requires that F n must be constant for the exactly linear spectrum (or decrease at least exponentially with n) [9]. For the sake of simplicity (a minimal number of inputs), we will assume that F n represent just a universal constant in the large-N c limit, F n = F .…”

“…of both sides in (1). Such planar sum rules were considered many times in the case of the linear Regge ansatz for radial spectrum motivated by the phenomenology [9,10],…”

Semileptonic tau decays beyond the Standard Model

“…This approximation works very precisely if the upper limit of the integral, s 0 , is large enough, except maybe near the positive real axis. In the previous expression, δ DV (s 0 ; n) accounts for the small deviations from it, known as quark-hadron Duality Violations (DV) [3][4][5][165][166][167][168][169].…”

Quantum entanglement in the initial and final state of relativistic heavy ion collisions

“…Historically parton-hadron duality was used to explain the perturbative part of the spectrum in elementary collisions [13], but the apparent similarity between the gluon densities required to explain the nuclear suppression factors measured in relativistic heavy-ion collisions at RHIC and the number of charged hadrons measured in the detector can also lead to the application of the model in larger multi-body systems [14]. In this picture the gluon saturation scale will determine the final state hadron multiplicities.…”