I believe you trying to see where user is getting Authenticated (against which user directory) .
Option #1 :
There is a default HTTP headers which carries the name of the directory against which the Policy Server authenticates the user.
Default HTTP Headers Used by the Product - CA Single Sign-On - 12.52 SP1 - CA Technologies Documentation
HTTP_SM_AUTHDIRNAME
Indicates the name of the directory against which the Policy Server authenticates the user. The administrator specifies this directory with the Administrative UI.
Option #2 :
Below are log snippets from smtracedefault.log which has references to the Authenticated User directory.
[11/27/2018][10:32:14.405][10:32:14][6724][6968][SmAuthUser.cpp:5289][CSmAuthUser::Authenticate][][][][][][][][][][][][][][][][][][][][][Enter function CSmAuthUser::Authenticate]
[11/27/2018][10:32:14.405][10:32:14][6724][6968][SmAuthUser.cpp:5440][CSmAuthUser::Authenticate][][][][ashokpearl][][][][CA-Dir-UserStore][][][][][][][][][][][][LDAP://mutas02-S11981:2389/uid=ashokpearl,ou=Users,o=sso,c=US][Authenticating user by the auth scheme]
[11/27/2018][10:32:14.405][10:32:14][6724][6968][SmAuthHtml.cpp:279][SmAuthenticate][][][][][][][][][][][][][][][][][][][][][Enter function SmAuthenticate]
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[11/27/2018][10:32:14.405][10:32:14][6724][6968][Sm_Auth_Message.cpp:5405][CSm_Auth_Message::FormatAttribute][s17/r4][iis.agent][][ashokpearl][][DisplayHTTPHeaders.asp][111Ashoktest][CA-Dir-UserStore][][][][][][][][][][][][LDAP:][Send response attribute 215, data size is 5]
[11/27/2018][10:32:14.405][10:32:14][6724][6968][Sm_Auth_Message.cpp:4902][CSm_Auth_Message::SendReply][s17/r4][iis.agent][][ashokpearl][][DisplayHTTPHeaders.asp][111Ashoktest][CA-Dir-UserStore][][][][][][][][][][][][][** Status: Authenticated. ]
[11/27/2018][10:32:14.405][10:32:14][6724][6968][Sm_Auth_Message.cpp:4906][CSm_Auth_Message::SendReply][][][][][][][][][][][][][][][][][][][][][Leave function CSm_Auth_Message::SendReply]
Regards
Ashok