## Collectivity from interference

## Abstract

In hadronic collisions, interference between different production channels affects momentum distributions of multi-particle final states. As this QCD interference does not depend on the strong coupling constant α s , it is part of the no-interaction baseline that needs to be controlled prior to searching for other manifestations of collective dynamics, e.g., in the analysis of azimuthal anisostropy coefficients v n at the LHC. Here, we introduce a model that is based on the QCD theory of multi-parton interactions and that allows one to study interference effects in the production of m particles in hadronic collisions with N parton-parton interactions (“sources”). In an expansion in powers of 1/( *N* _{c} ^{2} – 1) and to leading order in the number of sources *N*, we calculate interference effects in the m-particle spectra and we determine from them the second and fourth order cumulant momentum anisotropies v _{n} {2} and v _{n} {4}. Without invoking any azimuthal asymmetry and any density dependent non-linear dynamics in the incoming state, and without invoking any interaction in the final state, we find that QCD interference alone can give rise to values for v _{n} {2} and v _{n} {4}, n even, that persist unattenuated formore »

- Authors:

- Technion-Israel Inst. of Tech., Haifa (Israel). Dept. of Physics
- Univ. of Sao Paulo, Sao Paulo (Brazil). Dept. of Applied Mathematics
- Pennsylvania State Univ., University Park, PA (United States). Dept of Physics
- European Organization for Nuclear Research (CERN), Geneva (Switzerland). Theoretical Physics Dept.

- Publication Date:

- Research Org.:
- Pennsylvania State Univ., University Park, PA (United States)

- Sponsoring Org.:
- USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)

- OSTI Identifier:
- 1507416

- Grant/Contract Number:
- FG02-93ER40771

- Resource Type:
- Accepted Manuscript

- Journal Name:
- Journal of High Energy Physics (Online)

- Additional Journal Information:
- Journal Name: Journal of High Energy Physics (Online); Journal Volume: 2017; Journal Issue: 12; Journal ID: ISSN 1029-8479

- Publisher:
- Springer Berlin

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Heavy Ion Phenomenology

### Citation Formats

```
Blok, Boris, Jäkel, Christian D., Strikman, Mark, and Wiedemann, Urs Achim. Collectivity from interference. United States: N. p., 2017.
Web. doi:10.1007/jhep12(2017)074.
```

```
Blok, Boris, Jäkel, Christian D., Strikman, Mark, & Wiedemann, Urs Achim. Collectivity from interference. United States. doi:10.1007/jhep12(2017)074.
```

```
Blok, Boris, Jäkel, Christian D., Strikman, Mark, and Wiedemann, Urs Achim. Thu .
"Collectivity from interference". United States. doi:10.1007/jhep12(2017)074. https://www.osti.gov/servlets/purl/1507416.
```

```
@article{osti_1507416,
```

title = {Collectivity from interference},

author = {Blok, Boris and Jäkel, Christian D. and Strikman, Mark and Wiedemann, Urs Achim},

abstractNote = {In hadronic collisions, interference between different production channels affects momentum distributions of multi-particle final states. As this QCD interference does not depend on the strong coupling constant α s , it is part of the no-interaction baseline that needs to be controlled prior to searching for other manifestations of collective dynamics, e.g., in the analysis of azimuthal anisostropy coefficients v n at the LHC. Here, we introduce a model that is based on the QCD theory of multi-parton interactions and that allows one to study interference effects in the production of m particles in hadronic collisions with N parton-parton interactions (“sources”). In an expansion in powers of 1/(Nc2 – 1) and to leading order in the number of sources N, we calculate interference effects in the m-particle spectra and we determine from them the second and fourth order cumulant momentum anisotropies v n {2} and v n {4}. Without invoking any azimuthal asymmetry and any density dependent non-linear dynamics in the incoming state, and without invoking any interaction in the final state, we find that QCD interference alone can give rise to values for v n {2} and v n {4}, n even, that persist unattenuated for increasing number of sources, that may increase with increasing multiplicity and that agree with measurements in proton-proton (pp) collisions in terms of the order of magnitude of the signal and the approximate shape of the transverse momentum dependence. We further find that the non-abelian features of QCD interference can give rise to odd harmonic anisotropies. These findings indicate that the no-interaction baseline including QCD interference effects can make a sizeable if not dominant contribution to the measured v n coefficients in pp collisions. Prospects for analyzing QCD interference contributions further and their possible relevance for proton-nucleus and nucleus-nucleus collisions are discussed shortly.},

doi = {10.1007/jhep12(2017)074},

journal = {Journal of High Energy Physics (Online)},

number = 12,

volume = 2017,

place = {United States},

year = {2017},

month = {12}

}