Common femtoscopic hadron-emission source in pp collisions at the LHC
S. Acharya, D. Adamová, G. Aglieri Rinella, M. Agnello, N. Agrawal, Z. Ahammed, S. Ahmad, S. U. Ahn, I. Ahuja, A. Akindinov, M. Al-Turany, D. Aleksandrov, B. Alessandro, H. M. Alfanda, R. Alfaro Molina, Bushra Ali, A. Alici, N. Alizadehvandchali, A. Alkin, J. Alme, G. Alocco, T. Alt, Anna Rita Altamura, I. Altsybeev, Jesús Ricardo Alvarado García, M. N. Anaam, C. Andrei, N. Andreou, A. Andronic, Evgeny Andronov, V. Anguelov, F. Antinori, P. Antonioli, N. Apadula, L. Aphecetche, H. Appelshäuser, C. Arata, S. Arcelli, M. Aresti, R. Arnaldi, Jhoao Gabriel Martins Campos Almeida Arneiro, I. C. Arsene, M. Arslandok, A. Augustinus, R. Averbeck, M. D. Azmi, H. Baba, A. Badalà, J. Bae, Y. W. Baek, X. Bai, R. Bailhache, Y. Bailung, R. Bala, A. Balbino, A. Baldisseri, Bartosz Baliś, D. Banerjee, Z. Banoo, F. Barile, L. Barioglio, M. Barlou, Banajit Barman, G. G. Barnaföldi, L. S. Barnby, E. Barreau, V. Barret, L. Barreto, C. Bartels, K. Barth, E. Bartsch, N. Bastid, S. Basu, G. Batigne, D. Battistini, B. Batyunya, D. Bauri, J. L. Bazo Alba, I. G. Bearden, C. Beattie, P. Becht, D. Behera, I. Belikov, A. D. C. Bell Hechavarria, F. Bellini, R. Bellwied, S. Belokurova, L. G. E. Beltran, Yael Antonio Vásquez Beltran, G. Bencédi, S. Beolè, Y. Berdnikov, A. Berdnikova, L. Bergmann, Mihaela Gabriela Besoiu, L. Betev, Partha Pratim Bhaduri, A. Bhasin, M. A. Bhat, B. Bhattacharjee
Abstract
Abstract The femtoscopic study of pairs of identical pions is particularly suited to investigate the effective source function of particle emission, due to the resulting Bose–Einstein correlation signal. In small collision systems at the LHC, pp in particular, the majority of the pions are produced in resonance decays, which significantly affect the profile and size of the source. In this work, we explicitly model this effect in order to extract the primordial source in pp collisions at $$\sqrt{s}~=~13$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mspace/> <mml:mo>=</mml:mo> <mml:mspace/> <mml:mn>13</mml:mn> </mml:mrow> </mml:math> TeV from charged $$\uppi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>π</mml:mi> </mml:math> – $$\uppi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>π</mml:mi> </mml:math> correlations measured by ALICE. We demonstrate that the assumption of a Gaussian primordial source is compatible with the data and that the effective source, resulting from modifications due to resonances, is approximately exponential, as found in previous measurements at the LHC. The universality of hadron emission in pp collisions is further investigated by applying the same methodology to characterize the primordial source of $$\textrm{K}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mtext>K</mml:mtext> </mml:math> – $$\textrm{p}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mtext>p</mml:mtext> </mml:math> pairs. The size of the primordial source is evaluated as a function of the transverse mass ( $$m_{\textrm{T}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:mtext>T</mml:mtext> </mml:msub> </mml:math> ) of the pairs, leading to the observation of a common scaling for both $$\uppi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>π</mml:mi> </mml:math> – $$\uppi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>π</mml:mi> </mml:math> and $$\textrm{K}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mtext>K</mml:mtext> </mml:math> – $$\textrm{p}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mtext>p</mml:mtext> </mml:math> , suggesting a collective effect. Further, the present results are compatible with the $$m_{\textrm{T}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>m</mml:mi> <mml:mtext>T</mml:mtext> </mml:msub> </mml:math> scaling of the $$\textrm{p}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mtext>p</mml:mtext> </mml:math> – $$\textrm{p}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mtext>p</mml:mtext> </mml:math> and p $$-\Lambda $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>-</mml:mo> <mml:mi>Λ</mml:mi> </mml:mrow> </mml:math> primordial source measured by ALICE in high multiplicity pp collisions, providing additional evidence for the presence of a common emission source for all hadrons in small collision systems at the LHC. This will allow the determination of the source function for any hadron–hadron pairs with high precision, granting access to the properties of the possible final-state interaction among pairs of less abundantly produced hadrons, such as strange or charmed particles.